Remove useless docs

5 files changed, 0 insertions, 12232 deletions

diff --git a/libs/freeimage/src/LibPNG/CHANGES b/libs/freeimage/src/LibPNG/CHANGES
deleted file mode 100644
index 4b82118910..0000000000
--- a/libs/freeimage/src/LibPNG/CHANGES
+++ /dev/null
@@ -1,6051 +0,0 @@
-#if 0
-CHANGES - changes for libpng
-
-version 0.1 [March 29, 1995]
-  initial work-in-progress release
-
-version 0.2 [April 1, 1995]
-  added reader into png.h
-  fixed small problems in stub file
-
-version 0.3 [April 8, 1995]
-  added pull reader
-  split up pngwrite.c to several files
-  added pnglib.txt
-  added example.c
-  cleaned up writer, adding a few new transformations
-  fixed some bugs in writer
-  interfaced with zlib 0.5
-  added K&R support
-  added check for 64 KB blocks for 16 bit machines
-
-version 0.4 [April 26, 1995]
-  cleaned up code and commented code
-  simplified time handling into png_time
-  created png_color_16 and png_color_8 to handle color needs
-  cleaned up color type defines
-  fixed various bugs
-  made various names more consistent
-  interfaced with zlib 0.71
-  cleaned up zTXt reader and writer (using zlib's Reset functions)
-  split transformations into pngrtran.c and pngwtran.c
-
-version 0.5 [April 30, 1995]
-  interfaced with zlib 0.8
-  fixed many reading and writing bugs
-  saved using 3 spaces instead of tabs
-
-version 0.6 [May 1, 1995]
-  first beta release
-  added png_large_malloc() and png_large_free()
-  added png_size_t
-  cleaned up some compiler warnings
-  added png_start_read_image()
-
-version 0.7 [June 24, 1995]
-  cleaned up lots of bugs
-  finished dithering and other stuff
-  added test program
-  changed name from pnglib to libpng
-
-version 0.71 [June 26, 1995]
-  changed pngtest.png for zlib 0.93
-  fixed error in libpng.txt and example.c
-
-version 0.8 [August 20, 1995]
-  cleaned up some bugs
-  added png_set_filler()
-  split up pngstub.c into pngmem.c, pngio.c, and pngerror.c
-  added #define's to remove unwanted code
-  moved png_info_init() to png.c
-  added old_size into png_realloc()
-  added functions to manually set filtering and compression info
-  changed compression parameters based on image type
-  optimized filter selection code
-  added version info
-  changed external functions passing floats to doubles (k&r problems?)
-  put all the configurable stuff in pngconf.h
-  enabled png_set_shift to work with paletted images on read
-  added png_read_update_info() - updates info structure with transformations
-
-Version 0.81 [August, 1995]
-  incorporated Tim Wegner's medium model code (thanks, Tim)
-
-Version 0.82 [September, 1995]
-  [unspecified changes]
-
-Version 0.85 [December, 1995]
-  added more medium model code (almost everything's a far)
-  added i/o, error, and memory callback functions
-  fixed some bugs (16-bit, 4-bit interlaced, etc.)
-  added first run progressive reader (barely tested)
-
-Version 0.86 [January, 1996]
-  fixed bugs
-  improved documentation
-
-Version 0.87 [January, 1996]
-  fixed medium model bugs
-  fixed other bugs introduced in 0.85 and 0.86
-  added some minor documentation
-
-Version 0.88 [January, 1996]
-  fixed progressive bugs
-  replaced tabs with spaces
-  cleaned up documentation
-  added callbacks for read/write and warning/error functions
-
-Version 0.89 [June 5, 1996]
-  Added new initialization API to make libpng work better with shared libs
-    we now have png_create_read_struct(), png_create_write_struct(),
-    png_create_info_struct(), png_destroy_read_struct(), and
-    png_destroy_write_struct() instead of the separate calls to
-    malloc and png_read_init(), png_info_init(), and png_write_init()
-  Changed warning/error callback functions to fix bug - this means you
-    should use the new initialization API if you were using the old
-    png_set_message_fn() calls, and that the old API no longer exists
-    so that people are aware that they need to change their code
-  Changed filter selection API to allow selection of multiple filters
-    since it didn't work in previous versions of libpng anyways
-  Optimized filter selection code
-  Fixed png_set_background() to allow using an arbitrary RGB color for
-    paletted images
-  Fixed gamma and background correction for paletted images, so
-    png_correct_palette is not needed unless you are correcting an
-    external palette (you will need to #define PNG_CORRECT_PALETTE_SUPPORTED
-    in pngconf.h) - if nobody uses this, it may disappear in the future.
-  Fixed bug with Borland 64K memory allocation (Alexander Lehmann)
-  Fixed bug in interlace handling (Smarasderagd, I think)
-  Added more error checking for writing and image to reduce invalid files
-  Separated read and write functions so that they won't both be linked
-    into a binary when only reading or writing functionality is used
-  New pngtest image also has interlacing and zTXt
-  Updated documentation to reflect new API
-
-Version 0.89c [June 17, 1996]
-  Bug fixes.
-
-Version 0.90 [January, 1997]
-  Made CRC errors/warnings on critical and ancillary chunks configurable
-  libpng will use the zlib CRC routines by (compile-time) default
-  Changed DOS small/medium model memory support - needs zlib 1.04 (Tim Wegner)
-  Added external C++ wrapper statements to png.h (Gilles Dauphin)
-  Allow PNG file to be read when some or all of file signature has already
-    been read from the beginning of the stream.  ****This affects the size
-    of info_struct and invalidates all programs that use a shared libpng****
-  Fixed png_filler() declarations
-  Fixed? background color conversions
-  Fixed order of error function pointers to match documentation
-  Current chunk name is now available in png_struct to reduce the number
-    of nearly identical error messages (will simplify multi-lingual
-    support when available)
-  Try to get ready for unknown-chunk callback functions:
-    - previously read critical chunks are flagged, so the chunk handling
-      routines can determine if the chunk is in the right place
-    - all chunk handling routines have the same prototypes, so we will
-      be able to handle all chunks via a callback mechanism
-  Try to fix Linux "setjmp" buffer size problems
-  Removed png_large_malloc, png_large_free, and png_realloc functions.
-
-Version 0.95 [March, 1997]
-  Fixed bug in pngwutil.c allocating "up_row" twice and "avg_row" never
-  Fixed bug in PNG file signature compares when start != 0
-  Changed parameter type of png_set_filler(...filler...) from png_byte
-    to png_uint_32
-  Added test for MACOS to ensure that both math.h and fp.h are not #included
-  Added macros for libpng to be compiled as a Windows DLL (Andreas Kupries)
-  Added "packswap" transformation, which changes the endianness of
-    packed-pixel bytes (Kevin Bracey)
-  Added "strip_alpha" transformation, which removes the alpha channel of
-    input images without using it (not necessarily a good idea)
-  Added "swap_alpha" transformation, which puts the alpha channel in front
-    of the color bytes instead of after
-  Removed all implicit variable tests which assume NULL == 0 (I think)
-  Changed several variables to "png_size_t" to show 16/32-bit limitations
-  Added new pCAL chunk read/write support
-  Added experimental filter selection weighting (Greg Roelofs)
-  Removed old png_set_rgbx() and png_set_xrgb() functions that have been
-    obsolete for about 2 years now (use png_set_filler() instead)
-  Added macros to read 16- and 32-bit ints directly from buffer, to be
-    used only on those systems that support it (namely PowerPC and 680x0)
-    With some testing, this may become the default for MACOS/PPC systems.
-  Only calculate CRC on data if we are going to use it
-  Added macros for zTXt compression type PNG_zTXt_COMPRESSION_???
-  Added macros for simple libpng debugging output selectable at compile time
-  Removed PNG_READ_END_MODE in progressive reader (Smarasderagd)
-  More description of info_struct in libpng.txt and png.h
-  More instructions in example.c
-  More chunk types tested in pngtest.c
-  Renamed pngrcb.c to pngset.c, and all png_read_<chunk> functions to be
-    png_set_<chunk>.  We now have corresponding png_get_<chunk>
-    functions in pngget.c to get information in info_ptr.  This isolates
-    the application from the internal organization of png_info_struct
-    (good for shared library implementations).
-
-Version 0.96 [May, 1997]
-  Fixed serious bug with < 8bpp images introduced in 0.95
-  Fixed 256-color transparency bug (Greg Roelofs)
-  Fixed up documentation (Greg Roelofs, Laszlo Nyul)
-  Fixed "error" in pngconf.h for Linux setjmp() behavior
-  Fixed DOS medium model support (Tim Wegner)
-  Fixed png_check_keyword() for case with error in static string text
-  Added read of CRC after IEND chunk for embedded PNGs (Laszlo Nyul)
-  Added typecasts to quiet compiler errors
-  Added more debugging info
-
-Version 0.97 [January, 1998]
-  Removed PNG_USE_OWN_CRC capability
-  Relocated png_set_crc_action from pngrutil.c to pngrtran.c
-  Fixed typecasts of "new_key", etc. (Andreas Dilger)
-  Added RFC 1152 [sic] date support
-  Fixed bug in gamma handling of 4-bit grayscale
-  Added 2-bit grayscale gamma handling (Glenn R-P)
-  Added more typecasts. 65536L becomes (png_uint_32)65536L, etc. (Glenn R-P)
-  Minor corrections in libpng.txt
-  Added simple sRGB support (Glenn R-P)
-  Easier conditional compiling, e.g.,
-    define PNG_READ/WRITE_NOT_FULLY_SUPPORTED;
-    all configurable options can be selected from command-line instead
-    of having to edit pngconf.h (Glenn R-P)
-  Fixed memory leak in pngwrite.c (free info_ptr->text) (Glenn R-P)
-  Added more conditions for png_do_background, to avoid changing
-    black pixels to background when a background is supplied and
-    no pixels are transparent
-  Repaired PNG_NO_STDIO behavior
-  Tested NODIV support and made it default behavior (Greg Roelofs)
-  Added "-m" option and PNGTEST_DEBUG_MEMORY to pngtest (John Bowler)
-  Regularized version numbering scheme and bumped shared-library major
-    version number to 2 to avoid problems with libpng 0.89 apps
-    (Greg Roelofs)
-
-Version 0.98 [January, 1998]
-  Cleaned up some typos in libpng.txt and in code documentation
-  Fixed memory leaks in pCAL chunk processing (Glenn R-P and John Bowler)
-  Cosmetic change "display_gamma" to "screen_gamma" in pngrtran.c
-  Changed recommendation about file_gamma for PC images to .51 from .45,
-    in example.c and libpng.txt, added comments to distinguish between
-    screen_gamma, viewing_gamma, and display_gamma.
-  Changed all references to RFC1152 to read RFC1123 and changed the
-    PNG_TIME_RFC1152_SUPPORTED macro to PNG_TIME_RFC1123_SUPPORTED
-  Added png_invert_alpha capability (Glenn R-P -- suggestion by Jon Vincent)
-  Changed srgb_intent from png_byte to int to avoid compiler bugs
-
-Version 0.99 [January 30, 1998]
-  Free info_ptr->text instead of end_info_ptr->text in pngread.c (John Bowler)
-  Fixed a longstanding "packswap" bug in pngtrans.c
-  Fixed some inconsistencies in pngconf.h that prevented compiling with
-    PNG_READ_GAMMA_SUPPORTED and PNG_READ_hIST_SUPPORTED undefined
-  Fixed some typos and made other minor rearrangement of libpng.txt (Andreas)
-  Changed recommendation about file_gamma for PC images to .50 from .51 in
-    example.c and libpng.txt, and changed file_gamma for sRGB images to .45
-  Added a number of functions to access information from the png structure
-    png_get_image_height(), etc. (Glenn R-P, suggestion by Brad Pettit)
-  Added TARGET_MACOS similar to zlib-1.0.8
-  Define PNG_ALWAYS_EXTERN when __MWERKS__ && WIN32 are defined
-  Added type casting to all png_malloc() function calls
-
-Version 0.99a [January 31, 1998]
-  Added type casts and parentheses to all returns that return a value.(Tim W.)
-
-Version 0.99b [February 4, 1998]
-  Added type cast png_uint_32 on malloc function calls where needed.
-  Changed type of num_hist from png_uint_32 to int (same as num_palette).
-  Added checks for rowbytes overflow, in case png_size_t is less than 32 bits.
-  Renamed makefile.elf to makefile.lnx.
-
-Version 0.99c [February 7, 1998]
-  More type casting.  Removed erroneous overflow test in pngmem.c.
-  Added png_buffered_memcpy() and png_buffered_memset(), apply them to rowbytes.
-  Added UNIX manual pages libpng.3 (incorporating libpng.txt) and  png.5.
-
-Version 0.99d [February 11, 1998]
-  Renamed "far_to_near()" "png_far_to_near()"
-  Revised libpng.3
-  Version 99c "buffered" operations didn't work as intended.  Replaced them
-    with png_memcpy_check() and png_memset_check().
-  Added many "if (png_ptr == NULL) return" to quell compiler warnings about
-    unused png_ptr, mostly in pngget.c and pngset.c.
-  Check for overlength tRNS chunk present when indexed-color PLTE is read.
-  Cleaned up spelling errors in libpng.3/libpng.txt
-  Corrected a problem with png_get_tRNS() which returned undefined trans array
-
-Version 0.99e [February 28, 1998]
-  Corrected png_get_tRNS() again.
-  Add parentheses for easier reading of pngget.c, fixed "||" should be "&&".
-  Touched up example.c to make more of it compileable, although the entire
-    file still can't be compiled (Willem van Schaik)
-  Fixed a bug in png_do_shift() (Bryan Tsai)
-  Added a space in png.h prototype for png_write_chunk_start()
-  Replaced pngtest.png with one created with zlib 1.1.1
-  Changed pngtest to report PASS even when file size is different (Jean-loup G.)
-  Corrected some logic errors in png_do_invert_alpha() (Chris Patterson)
-
-Version 0.99f [March 5, 1998]
-  Corrected a bug in pngpread() introduced in version 99c (Kevin Bracey)
-  Moved makefiles into a "scripts" directory, and added INSTALL instruction file
-  Added makefile.os2 and pngos2.def (A. Zabolotny) and makefile.s2x (W. Sebok)
-  Added pointers to "note on libpng versions" in makefile.lnx and README
-  Added row callback feature when reading and writing nonprogressive rows
-    and added a test of this feature in pngtest.c
-  Added user transform callbacks, with test of the feature in pngtest.c
-
-Version 0.99g [March 6, 1998, morning]
-  Minor changes to pngtest.c to suppress compiler warnings.
-  Removed "beta" language from documentation.
-
-Version 0.99h [March 6, 1998, evening]
-  Minor changes to previous minor changes to pngtest.c
-  Changed PNG_READ_NOT_FULLY_SUPPORTED to PNG_READ_TRANSFORMS_NOT_SUPPORTED
-    and added PNG_PROGRESSIVE_READ_NOT_SUPPORTED macro
-  Added user transform capability
-
-Version 1.00 [March 7, 1998]
-  Changed several typedefs in pngrutil.c
-  Added makefile.wat (Pawel Mrochen), updated makefile.tc3 (Willem van Schaik)
-  Replaced "while(1)" with "for(;;)"
-  Added PNGARG() to prototypes in pngtest.c and removed some prototypes
-  Updated some of the makefiles (Tom Lane)
-  Changed some typedefs (s_start, etc.) in pngrutil.c
-  Fixed dimensions of "short_months" array in pngwrite.c
-  Replaced ansi2knr.c with the one from jpeg-v6
-
-Version 1.0.0 [March 8, 1998]
-  Changed name from 1.00 to 1.0.0 (Adam Costello)
-  Added smakefile.ppc (with SCOPTIONS.ppc) for Amiga PPC (Andreas Kleinert)
-
-Version 1.0.0a [March 9, 1998]
-  Fixed three bugs in pngrtran.c to make gamma+background handling consistent
-    (Greg Roelofs)
-  Changed format of the PNG_LIBPNG_VER integer to xyyzz instead of xyz
-    for major, minor, and bugfix releases.  This is 10001. (Adam Costello,
-    Tom Lane)
-  Make months range from 1-12 in png_convert_to_rfc1123
-
-Version 1.0.0b [March 13, 1998]
-  Quieted compiler complaints about two empty "for" loops in pngrutil.c
-  Minor changes to makefile.s2x
-  Removed #ifdef/#endif around a png_free() in pngread.c
-
-Version 1.0.1 [March 14, 1998]
-  Changed makefile.s2x to reduce security risk of using a relative pathname
-  Fixed some typos in the documentation (Greg).
-  Fixed a problem with value of "channels" returned by png_read_update_info()
-
-Version 1.0.1a [April 21, 1998]
-  Optimized Paeth calculations by replacing abs() function calls with intrinsics
-  plus other loop optimizations. Improves avg decoding speed by about 20%.
-  Commented out i386istic "align" compiler flags in makefile.lnx.
-  Reduced the default warning level in some makefiles, to make them consistent.
-  Removed references to IJG and JPEG in the ansi2knr.c copyright statement.
-  Fixed a bug in png_do_strip_filler with XXRRGGBB => RRGGBB transformation.
-  Added grayscale and 16-bit capability to png_do_read_filler().
-  Fixed a bug in pngset.c, introduced in version 0.99c, that sets rowbytes
-    too large when writing an image with bit_depth < 8 (Bob Dellaca).
-  Corrected some bugs in the experimental weighted filtering heuristics.
-  Moved a misplaced pngrutil code block that truncates tRNS if it has more
-    than num_palette entries -- test was done before num_palette was defined.
-  Fixed a png_convert_to_rfc1123() bug that converts day 31 to 0 (Steve Eddins).
-  Changed compiler flags in makefile.wat for better optimization
-    (Pawel Mrochen).
-
-Version 1.0.1b [May 2, 1998]
-  Relocated png_do_gray_to_rgb() within png_do_read_transformations() (Greg).
-  Relocated the png_composite macros from pngrtran.c to png.h (Greg).
-  Added makefile.sco (contributed by Mike Hopkirk).
-  Fixed two bugs (missing definitions of "istop") introduced in libpng-1.0.1a.
-  Fixed a bug in pngrtran.c that would set channels=5 under some circumstances.
-  More work on the Paeth-filtering, achieving imperceptible speedup
-    (A Kleinert).
-  More work on loop optimization which may help when compiled with C++
-    compilers.
-  Added warnings when people try to use transforms they've defined out.
-  Collapsed 4 "i" and "c" loops into single "i" loops in pngrtran and pngwtran.
-  Revised paragraph about png_set_expand() in libpng.txt and libpng.3 (Greg)
-
-Version 1.0.1c [May 11, 1998]
-  Fixed a bug in pngrtran.c (introduced in libpng-1.0.1a) where the masks for
-    filler bytes should have been 0xff instead of 0xf.
-  Added max_pixel_depth=32 in pngrutil.c when using FILLER with palette images.
-  Moved PNG_WRITE_WEIGHTED_FILTER_SUPPORTED and PNG_WRITE_FLUSH_SUPPORTED
-    out of the PNG_WRITE_TRANSFORMS_NOT_SUPPORTED block of pngconf.h
-  Added "PNG_NO_WRITE_TRANSFORMS" etc., as alternatives for *_NOT_SUPPORTED,
-    for consistency, in pngconf.h
-  Added individual "ifndef PNG_NO_[CAPABILITY]" in pngconf.h to make it easier
-    to remove unwanted capabilities via the compile line
-  Made some corrections to grammar (which, it's) in documentation (Greg).
-  Corrected example.c, use of row_pointers in png_write_image().
-
-Version 1.0.1d [May 24, 1998]
-  Corrected several statements that used side effects illegally in pngrutil.c
-    and pngtrans.c, that were introduced in version 1.0.1b
-  Revised png_read_rows() to avoid repeated if-testing for NULL (A Kleinert)
-  More corrections to example.c, use of row_pointers in png_write_image()
-    and png_read_rows().
-  Added pngdll.mak and pngdef.pas to scripts directory, contributed by
-    Bob Dellaca, to make a png32bd.dll with Borland C++ 4.5
-  Fixed error in example.c with png_set_text: num_text is 3, not 2 (Guido V.)
-  Changed several loops from count-down to count-up, for consistency.
-
-Version 1.0.1e [June 6, 1998]
-  Revised libpng.txt and libpng.3 description of png_set_read|write_fn(), and
-    added warnings when people try to set png_read_fn and png_write_fn in
-    the same structure.
-  Added a test such that png_do_gamma will be done when num_trans==0
-    for truecolor images that have defined a background.  This corrects an
-    error that was introduced in libpng-0.90 that can cause gamma processing
-    to be skipped.
-  Added tests in png.h to include "trans" and "trans_values" in structures
-    when PNG_READ_BACKGROUND_SUPPORTED or PNG_READ_EXPAND_SUPPORTED is defined.
-  Add png_free(png_ptr->time_buffer) in png_destroy_read_struct()
-  Moved png_convert_to_rfc_1123() from pngwrite.c to png.c
-  Added capability for user-provided malloc_fn() and free_fn() functions,
-    and revised pngtest.c to demonstrate their use, replacing the
-    PNGTEST_DEBUG_MEM feature.
-  Added makefile.w32, for Microsoft C++ 4.0 and later (Tim Wegner).
-
-Version 1.0.2 [June 14, 1998]
-  Fixed two bugs in makefile.bor .
-
-Version 1.0.2a [December 30, 1998]
-  Replaced and extended code that was removed from png_set_filler() in 1.0.1a.
-  Fixed a bug in png_do_filler() that made it fail to write filler bytes in
-    the left-most pixel of each row (Kevin Bracey).
-  Changed "static pngcharp tIME_string" to "static char tIME_string[30]"
-    in pngtest.c (Duncan Simpson).
-  Fixed a bug in pngtest.c that caused pngtest to try to write a tIME chunk
-    even when no tIME chunk was present in the source file.
-  Fixed a problem in pngrutil.c: gray_to_rgb didn't always work with 16-bit.
-  Fixed a problem in png_read_push_finish_row(), which would not skip some
-    passes that it should skip, for images that are less than 3 pixels high.
-  Interchanged the order of calls to png_do_swap() and png_do_shift()
-    in pngwtran.c (John Cromer).
-  Added #ifdef PNG_DEBUG/#endif surrounding use of PNG_DEBUG in png.h .
-  Changed "bad adaptive filter type" from error to warning in pngrutil.c .
-  Fixed a documentation error about default filtering with 8-bit indexed-color.
-  Separated the PNG_NO_STDIO macro into PNG_NO_STDIO and PNG_NO_CONSOLE_IO
-    (L. Peter Deutsch).
-  Added png_set_rgb_to_gray() and png_get_rgb_to_gray_status() functions.
-  Added png_get_copyright() and png_get_header_version() functions.
-  Revised comments on png_set_progressive_read_fn() in libpng.txt and example.c
-  Added information about debugging in libpng.txt and libpng.3 .
-  Changed "ln -sf" to "ln -s -f" in makefile.s2x, makefile.lnx, and
-    makefile.sco.
-  Removed lines after Dynamic Dependencies" in makefile.aco .
-  Revised makefile.dec to make a shared library (Jeremie Petit).
-  Removed trailing blanks from all files.
-
-Version 1.0.2a [January 6, 1999]
-  Removed misplaced #endif and #ifdef PNG_NO_EXTERN near the end of png.h
-  Added "if" tests to silence complaints about unused png_ptr in png.h and png.c
-  Changed "check_if_png" function in example.c to return true (nonzero) if PNG.
-  Changed libpng.txt to demonstrate png_sig_cmp() instead of png_check_sig()
-    which is obsolete.
-
-Version 1.0.3 [January 14, 1999]
-  Added makefile.hux, for Hewlett Packard HPUX 10.20 and 11.00 (Jim Rice)
-  Added a statement of Y2K compliance in png.h, libpng.3, and Y2KINFO.
-
-Version 1.0.3a [August 12, 1999]
-  Added check for PNG_READ_INTERLACE_SUPPORTED in pngread.c; issue a warning
-    if an attempt is made to read an interlaced image when it's not supported.
-  Added check if png_ptr->trans is defined before freeing it in pngread.c
-  Modified the Y2K statement to include versions back to version 0.71
-  Fixed a bug in the check for valid IHDR bit_depth/color_types in pngrutil.c
-  Modified makefile.wat (added -zp8 flag, ".symbolic", changed some comments)
-  Replaced leading blanks with tab characters in makefile.hux
-  Changed "dworkin.wustl.edu" to "ccrc.wustl.edu" in various documents.
-  Changed (float)red and (float)green to (double)red, (double)green
-    in png_set_rgb_to_gray() to avoid "promotion" problems in AIX.
-  Fixed a bug in pngconf.h that omitted <stdio.h> when PNG_DEBUG==0 (K Bracey).
-  Reformatted libpng.3 and libpngpf.3 with proper fonts (script by J. vanZandt).
-  Updated documentation to refer to the PNG-1.2 specification.
-  Removed ansi2knr.c and left pointers to the latest source for ansi2knr.c
-    in makefile.knr, INSTALL, and README (L. Peter Deutsch)
-  Fixed bugs in calculation of the length of rowbytes when adding alpha
-    channels to 16-bit images, in pngrtran.c (Chris Nokleberg)
-  Added function png_set_user_transform_info() to store user_transform_ptr,
-    user_depth, and user_channels into the png_struct, and a function
-    png_get_user_transform_ptr() to retrieve the pointer (Chris Nokleberg)
-  Added function png_set_empty_plte_permitted() to make libpng useable
-    in MNG applications.
-  Corrected the typedef for png_free_ptr in png.h (Jesse Jones).
-  Correct gamma with srgb is 45455 instead of 45000 in pngrutil.c, to be
-    consistent with PNG-1.2, and allow variance of 500 before complaining.
-  Added assembler code contributed by Intel in file pngvcrd.c and modified
-    makefile.w32 to use it (Nirav Chhatrapati, INTEL Corporation,
-    Gilles Vollant)
-  Changed "ln -s -f" to "ln -f -s" in the makefiles to make Solaris happy.
-  Added some aliases for png_set_expand() in pngrtran.c, namely
-    png_set_expand_PLTE(), png_set_expand_depth(), and png_set_expand_tRNS()
-    (Greg Roelofs, in "PNG: The Definitive Guide").
-  Added makefile.beo for BEOS on X86, contributed by Sander Stok.
-
-Version 1.0.3b [August 26, 1999]
-  Replaced 2147483647L several places with PNG_MAX_UINT macro, defined in png.h
-  Changed leading blanks to tabs in all makefiles.
-  Define PNG_USE_PNGVCRD in makefile.w32, to get MMX assembler code.
-  Made alternate versions of  png_set_expand() in pngrtran.c, namely
-    png_set_gray_1_2_4_to_8, png_set_palette_to_rgb, and png_set_tRNS_to_alpha
-    (Greg Roelofs, in "PNG: The Definitive Guide").  Deleted the 1.0.3a aliases.
-  Relocated start of 'extern "C"' block in png.h so it doesn't include pngconf.h
-  Revised calculation of num_blocks in pngmem.c to avoid a potentially
-    negative shift distance, whose results are undefined in the C language.
-  Added a check in pngset.c to prevent writing multiple tIME chunks.
-  Added a check in pngwrite.c to detect invalid small window_bits sizes.
-
-Version 1.0.3d [September 4, 1999]
-  Fixed type casting of igamma in pngrutil.c
-  Added new png_expand functions to scripts/pngdef.pas and pngos2.def
-  Added a demo read_user_transform_fn that examines the row filters in pngtest.c
-
-Version 1.0.4 [September 24, 1999, not distributed publicly]
-  Define PNG_ALWAYS_EXTERN in pngconf.h if __STDC__ is defined
-  Delete #define PNG_INTERNAL and include "png.h" from pngasmrd.h
-  Made several minor corrections to pngtest.c
-  Renamed the makefiles with longer but more user friendly extensions.
-  Copied the PNG copyright and license to a separate LICENSE file.
-  Revised documentation, png.h, and example.c to remove reference to
-    "viewing_gamma" which no longer appears in the PNG specification.
-  Revised pngvcrd.c to use MMX code for interlacing only on the final pass.
-  Updated pngvcrd.c to use the faster C filter algorithms from libpng-1.0.1a
-  Split makefile.win32vc into two versions, makefile.vcawin32 (uses MMX
-    assembler code) and makefile.vcwin32 (doesn't).
-  Added a CPU timing report to pngtest.c (enabled by defining PNGTEST_TIMING)
-  Added a copy of pngnow.png to the distribution.
-
-Version 1.0.4a [September 25, 1999]
-  Increase max_pixel_depth in pngrutil.c if a user transform needs it.
-  Changed several division operations to right-shifts in pngvcrd.c
-
-Version 1.0.4b [September 30, 1999]
-  Added parentheses in line 3732 of pngvcrd.c
-  Added a comment in makefile.linux warning about buggy -O3 in pgcc 2.95.1
-
-Version 1.0.4c [October 1, 1999]
-  Added a "png_check_version" function in png.c and pngtest.c that will generate
-    a helpful compiler error if an old png.h is found in the search path.
-  Changed type of png_user_transform_depth|channels from int to png_byte.
-  Added "Libpng is OSI Certified Open Source Software" statement to png.h
-
-Version 1.0.4d [October 6, 1999]
-  Changed 0.45 to 0.45455 in png_set_sRGB()
-  Removed unused PLTE entries from pngnow.png
-  Re-enabled some parts of pngvcrd.c (png_combine_row) that work properly.
-
-Version 1.0.4e [October 10, 1999]
-  Fixed sign error in pngvcrd.c (Greg Roelofs)
-  Replaced some instances of memcpy with simple assignments in pngvcrd (GR-P)
-
-Version 1.0.4f [October 15, 1999]
-  Surrounded example.c code with #if 0 .. #endif to prevent people from
-    inadvertently trying to compile it.
-  Changed png_get_header_version() from a function to a macro in png.h
-  Added type casting mostly in pngrtran.c and pngwtran.c
-  Removed some pointless "ptr = NULL" in pngmem.c
-  Added a "contrib" directory containing the source code from Greg's book.
-
-Version 1.0.5 [October 15, 1999]
-  Minor editing of the INSTALL and README files.
-
-Version 1.0.5a [October 23, 1999]
-  Added contrib/pngsuite and contrib/pngminus (Willem van Schaik)
-  Fixed a typo in the png_set_sRGB() function call in example.c (Jan Nijtmans)
-  Further optimization and bugfix of pngvcrd.c
-  Revised pngset.c so that it does not allocate or free memory in the user's
-    text_ptr structure.  Instead, it makes its own copy.
-  Created separate write_end_info_struct in pngtest.c for a more severe test.
-  Added code in pngwrite.c to free info_ptr->text[i].key to stop a memory leak.
-
-Version 1.0.5b [November 23, 1999]
-  Moved PNG_FLAG_HAVE_CHUNK_HEADER, PNG_FLAG_BACKGROUND_IS_GRAY and
-    PNG_FLAG_WROTE_tIME from flags to mode.
-  Added png_write_info_before_PLTE() function.
-  Fixed some typecasting in contrib/gregbook/*.c
-  Updated scripts/makevms.com and added makevms.com to contrib/gregbook
-    and contrib/pngminus (Martin Zinser)
-
-Version 1.0.5c [November 26, 1999]
-  Moved png_get_header_version from png.h to png.c, to accommodate ansi2knr.
-  Removed all global arrays (according to PNG_NO_GLOBAL_ARRAYS macro), to
-    accommodate making DLL's: Moved usr_png_ver from global variable to function
-    png_get_header_ver() in png.c.  Moved png_sig to png_sig_bytes in png.c and
-    eliminated use of png_sig in pngwutil.c.  Moved the various png_CHNK arrays
-    into pngtypes.h.  Eliminated use of global png_pass arrays.  Declared the
-    png_CHNK and png_pass arrays to be "const".  Made the global arrays
-    available to applications (although none are used in libpng itself) when
-    PNG_NO_GLOBAL_ARRAYS is not defined or when PNG_GLOBAL_ARRAYS is defined.
-  Removed some extraneous "-I" from contrib/pngminus/makefile.std
-  Changed the PNG_sRGB_INTENT macros in png.h to be consistent with PNG-1.2.
-  Change PNG_SRGB_INTENT to PNG_sRGB_INTENT in libpng.txt and libpng.3
-
-Version 1.0.5d [November 29, 1999]
-  Add type cast (png_const_charp) two places in png.c
-  Eliminated pngtypes.h; use macros instead to declare PNG_CHNK arrays.
-  Renamed "PNG_GLOBAL_ARRAYS" to "PNG_USE_GLOBAL_ARRAYS" and made available
-    to applications a macro "PNG_USE_LOCAL_ARRAYS".
-  comment out (with #ifdef) all the new declarations when
-    PNG_USE_GLOBAL_ARRAYS is defined.
-  Added PNG_EXPORT_VAR macro to accommodate making DLL's.
-
-Version 1.0.5e [November 30, 1999]
-  Added iCCP, iTXt, and sPLT support; added "lang" member to the png_text
-    structure; refactored the inflate/deflate support to make adding new chunks
-    with trailing compressed parts easier in the future, and added new functions
-    png_free_iCCP, png_free_pCAL, png_free_sPLT, png_free_text, png_get_iCCP,
-    png_get_spalettes, png_set_iCCP, png_set_spalettes (Eric S. Raymond).
-    NOTE: Applications that write text chunks MUST define png_text->lang
-    before calling png_set_text(). It must be set to NULL if you want to
-    write tEXt or zTXt chunks.  If you want your application to be able to
-    run with older versions of libpng, use
-
-      #ifdef PNG_iTXt_SUPPORTED
-         png_text[i].lang = NULL;
-      #endif
-
-  Changed png_get_oFFs() and png_set_oFFs() to use signed rather than unsigned
-    offsets (Eric S. Raymond).
-  Combined PNG_READ_cHNK_SUPPORTED and PNG_WRITE_cHNK_SUPPORTED macros into
-    PNG_cHNK_SUPPORTED and combined the three types of PNG_text_SUPPORTED
-    macros, leaving the separate macros also available.
-  Removed comments on #endifs at the end of many short, non-nested #if-blocks.
-
-Version 1.0.5f [December 6, 1999]
-  Changed makefile.solaris to issue a warning about potential problems when
-    the ucb "ld" is in the path ahead of the ccs "ld".
-  Removed "- [date]" from the "synopsis" line in libpng.3 and libpngpf.3.
-  Added sCAL chunk support (Eric S. Raymond).
-
-Version 1.0.5g [December 7, 1999]
-  Fixed "png_free_spallettes" typo in png.h
-  Added code to handle new chunks in pngpread.c
-  Moved PNG_CHNK string macro definitions outside of PNG_NO_EXTERN block
-  Added "translated_key" to png_text structure and png_write_iTXt().
-  Added code in pngwrite.c to work around a newly discovered zlib bug.
-
-Version 1.0.5h [December 10, 1999]
-  NOTE: regarding the note for version 1.0.5e, the following must also
-    be included in your code:
-        png_text[i].translated_key = NULL;
-  Unknown chunk handling is now supported.
-  Option to eliminate all floating point support was added.  Some new
-    fixed-point functions such as png_set_gAMA_fixed() were added.
-  Expanded tabs and removed trailing blanks in source files.
-
-Version 1.0.5i [December 13, 1999]
-  Added some type casts to silence compiler warnings.
-  Renamed "png_free_spalette" to "png_free_spalettes" for consistency.
-  Removed leading blanks from a #define in pngvcrd.c
-  Added some parameters to the new png_set_keep_unknown_chunks() function.
-  Added a test for up->location != 0 in the first instance of writing
-    unknown chunks in pngwrite.c
-  Changed "num" to "i" in png_free_spalettes() and png_free_unknowns() to
-    prevent recursion.
-  Added png_free_hIST() function.
-  Various patches to fix bugs in the sCAL and integer cHRM processing,
-    and to add some convenience macros for use with sCAL.
-
-Version 1.0.5j [December 21, 1999]
-  Changed "unit" parameter of png_write_sCAL from png_byte to int, to work
-    around buggy compilers.
-  Added new type "png_fixed_point" for integers that hold float*100000 values
-  Restored backward compatibility of tEXt/zTXt chunk processing:
-    Restored the first four members of png_text to the same order as v.1.0.5d.
-    Added members "lang_key" and "itxt_length" to png_text struct.  Set
-    text_length=0 when "text" contains iTXt data.  Use the "compression"
-    member to distinguish among tEXt/zTXt/iTXt types.  Added
-    PNG_ITXT_COMPRESSION_NONE (1) and PNG_ITXT_COMPRESSION_zTXt(2) macros.
-    The "Note" above, about backward incompatibility of libpng-1.0.5e, no
-    longer applies.
-  Fixed png_read|write_iTXt() to read|write parameters in the right order,
-    and to write the iTXt chunk after IDAT if it appears in the end_ptr.
-  Added pnggccrd.c, version of pngvcrd.c Intel assembler for gcc (Greg Roelofs)
-  Reversed the order of trying to write floating-point and fixed-point gAMA.
-
-Version 1.0.5k [December 27, 1999]
-  Added many parentheses, e.g., "if (a && b & c)" becomes "if (a && (b & c))"
-  Added png_handle_as_unknown() function (Glenn)
-  Added png_free_chunk_list() function and chunk_list and num_chunk_list members
-    of png_ptr.
-  Eliminated erroneous warnings about multiple sPLT chunks and sPLT-after-PLTE.
-  Fixed a libpng-1.0.5h bug in pngrutil.c that was issuing erroneous warnings
-    about ignoring incorrect gAMA with sRGB (gAMA was in fact not ignored)
-  Added png_free_tRNS(); png_set_tRNS() now malloc's its own trans array (ESR).
-  Define png_get_int_32 when oFFs chunk is supported as well as when pCAL is.
-  Changed type of proflen from png_int_32 to png_uint_32 in png_get_iCCP().
-
-Version 1.0.5l [January 1, 2000]
-  Added functions png_set_read_user_chunk_fn() and png_get_user_chunk_ptr()
-    for setting a callback function to handle unknown chunks and for
-    retrieving the associated user pointer (Glenn).
-
-Version 1.0.5m [January 7, 2000]
-  Added high-level functions png_read_png(), png_write_png(), png_free_pixels().
-
-Version 1.0.5n [January 9, 2000]
-  Added png_free_PLTE() function, and modified png_set_PLTE() to malloc its
-    own memory for info_ptr->palette.  This makes it safe for the calling
-    application to free its copy of the palette any time after it calls
-    png_set_PLTE().
-
-Version 1.0.5o [January 20, 2000]
-  Cosmetic changes only (removed some trailing blanks and TABs)
-
-Version 1.0.5p [January 31, 2000]
-  Renamed pngdll.mak to makefile.bd32
-  Cosmetic changes in pngtest.c
-
-Version 1.0.5q [February 5, 2000]
-  Relocated the makefile.solaris warning about PATH problems.
-  Fixed pngvcrd.c bug by pushing/popping registers in mmxsupport (Bruce Oberg)
-  Revised makefile.gcmmx
-  Added PNG_SETJMP_SUPPORTED, PNG_SETJMP_NOT_SUPPORTED, and PNG_ABORT() macros
-
-Version 1.0.5r [February 7, 2000]
-  Removed superfluous prototype for png_get_itxt from png.h
-  Fixed a bug in pngrtran.c that improperly expanded the background color.
-  Return *num_text=0 from png_get_text() when appropriate, and fix documentation
-    of png_get_text() in libpng.txt/libpng.3.
-
-Version 1.0.5s [February 18, 2000]
-  Added "png_jmp_env()" macro to pngconf.h, to help people migrate to the
-    new error handler that's planned for the next libpng release, and changed
-    example.c, pngtest.c, and contrib programs to use this macro.
-  Revised some of the DLL-export macros in pngconf.h (Greg Roelofs)
-  Fixed a bug in png_read_png() that caused it to fail to expand some images
-    that it should have expanded.
-  Fixed some mistakes in the unused and undocumented INCH_CONVERSIONS functions
-    in pngget.c
-  Changed the allocation of palette, history, and trans arrays back to
-    the version 1.0.5 method (linking instead of copying) which restores
-    backward compatibility with version 1.0.5.  Added some remarks about
-    that in example.c.  Added "free_me" member to info_ptr and png_ptr
-    and added png_free_data() function.
-  Updated makefile.linux and makefile.gccmmx to make directories conditionally.
-  Made cosmetic changes to pngasmrd.h
-  Added png_set_rows() and png_get_rows(), for use with png_read|write_png().
-  Modified png_read_png() to allocate info_ptr->row_pointers only if it
-    hasn't already been allocated.
-
-Version 1.0.5t [March 4, 2000]
-  Changed png_jmp_env() migration aiding macro to png_jmpbuf().
-  Fixed "interlace" typo (should be "interlaced") in contrib/gregbook/read2-x.c
-  Fixed bug with use of PNG_BEFORE_IHDR bit in png_ptr->mode, introduced when
-    PNG_FLAG_HAVE_CHUNK_HEADER was moved into png_ptr->mode in version 1.0.5b
-  Files in contrib/gregbook were revised to use png_jmpbuf() and to select
-    a 24-bit visual if one is available, and to allow abbreviated options.
-  Files in contrib/pngminus were revised to use the png_jmpbuf() macro.
-  Removed spaces in makefile.linux and makefile.gcmmx, introduced in 1.0.5s
-
-Version 1.0.5u [March 5, 2000]
-  Simplified the code that detects old png.h in png.c and pngtest.c
-  Renamed png_spalette (_p, _pp) to png_sPLT_t (_tp, _tpp)
-  Increased precision of rgb_to_gray calculations from 8 to 15 bits and
-    added png_set_rgb_to_gray_fixed() function.
-  Added makefile.bc32 (32-bit Borland C++, C mode)
-
-Version 1.0.5v [March 11, 2000]
-  Added some parentheses to the png_jmpbuf macro definition.
-  Updated references to the zlib home page, which has moved to freesoftware.com.
-  Corrected bugs in documentation regarding png_read_row() and png_write_row().
-  Updated documentation of png_rgb_to_gray calculations in libpng.3/libpng.txt.
-  Renamed makefile.borland,turboc3 back to makefile.bor,tc3 as in version 1.0.3,
-    revised borland makefiles; added makefile.ibmvac3 and makefile.gcc (Cosmin)
-
-Version 1.0.6 [March 20, 2000]
-  Minor revisions of makefile.bor, libpng.txt, and gregbook/rpng2-win.c
-  Added makefile.sggcc (SGI IRIX with gcc)
-
-Version 1.0.6d [April 7, 2000]
-  Changed sprintf() to strcpy() in png_write_sCAL_s() to work without STDIO
-  Added data_length parameter to png_decompress_chunk() function
-  Revised documentation to remove reference to abandoned png_free_chnk functions
-  Fixed an error in png_rgb_to_gray_fixed()
-  Revised example.c, usage of png_destroy_write_struct().
-  Renamed makefile.ibmvac3 to makefile.ibmc, added libpng.icc IBM project file
-  Added a check for info_ptr->free_me&PNG_FREE_TEXT when freeing text in png.c
-  Simplify png_sig_bytes() function to remove use of non-ISO-C strdup().
-
-Version 1.0.6e [April 9, 2000]
-  Added png_data_freer() function.
-  In the code that checks for over-length tRNS chunks, added check of
-    info_ptr->num_trans as well as png_ptr->num_trans (Matthias Benckmann)
-  Minor revisions of libpng.txt/libpng.3.
-  Check for existing data and free it if the free_me flag is set, in png_set_*()
-    and png_handle_*().
-  Only define PNG_WEIGHTED_FILTERS_SUPPORTED when PNG_FLOATING_POINT_SUPPORTED
-    is defined.
-  Changed several instances of PNG_NO_CONSOLE_ID to PNG_NO_STDIO in pngrutil.c
-    and mentioned the purposes of the two macros in libpng.txt/libpng.3.
-
-Version 1.0.6f [April 14, 2000]
-  Revised png_set_iCCP() and png_set_rows() to avoid prematurely freeing data.
-  Add checks in png_set_text() for NULL members of the input text structure.
-  Revised libpng.txt/libpng.3.
-  Removed superfluous prototype for png_set_iTXt from png.h
-  Removed "else" from pngread.c, after png_error(), and changed "0" to "length".
-  Changed several png_errors about malformed ancillary chunks to png_warnings.
-
-Version 1.0.6g [April 24, 2000]
-  Added png_pass-* arrays to pnggccrd.c when PNG_USE_LOCAL_ARRAYS is defined.
-  Relocated paragraph about png_set_background() in libpng.3/libpng.txt
-    and other revisions (Matthias Benckmann)
-  Relocated info_ptr->free_me, png_ptr->free_me, and other info_ptr and
-    png_ptr members to restore binary compatibility with libpng-1.0.5
-    (breaks compatibility with libpng-1.0.6).
-
-Version 1.0.6h [April 24, 2000]
-  Changed shared library so-number pattern from 2.x.y.z to xy.z (this builds
-    libpng.so.10 & libpng.so.10.6h instead of libpng.so.2 & libpng.so.2.1.0.6h)
-    This is a temporary change for test purposes.
-
-Version 1.0.6i [May 2, 2000]
-  Rearranged some members at the end of png_info and png_struct, to put
-    unknown_chunks_num and free_me within the original size of the png_structs
-    and free_me, png_read_user_fn, and png_free_fn within the original png_info,
-    because some old applications allocate the structs directly instead of
-    using png_create_*().
-  Added documentation of user memory functions in libpng.txt/libpng.3
-  Modified png_read_png so that it will use user_allocated row_pointers
-    if present, unless free_me directs that it be freed, and added description
-    of the use of png_set_rows() and png_get_rows() in libpng.txt/libpng.3.
-  Added PNG_LEGACY_SUPPORTED macro, and #ifdef out all new (since version
-    1.00) members of png_struct and png_info, to regain binary compatibility
-    when you define this macro.  Capabilities lost in this event
-    are user transforms (new in version 1.0.0),the user transform pointer
-    (new in version 1.0.2), rgb_to_gray (new in 1.0.5), iCCP, sCAL, sPLT,
-    the high-level interface, and unknown chunks support (all new in 1.0.6).
-    This was necessary because of old applications that allocate the structs
-    directly as authors were instructed to do in libpng-0.88 and earlier,
-    instead of using png_create_*().
-  Added modes PNG_CREATED_READ_STRUCT and PNG_CREATED_WRITE_STRUCT which
-    can be used to detect codes that directly allocate the structs, and
-    code to check these modes in png_read_init() and png_write_init() and
-    generate a libpng error if the modes aren't set and PNG_LEGACY_SUPPORTED
-    was not defined.
-  Added makefile.intel and updated makefile.watcom (Pawel Mrochen)
-
-Version 1.0.6j [May 3, 2000]
-  Overloaded png_read_init() and png_write_init() with macros that convert
-    calls to png_read_init_2() or png_write_init_2() that check the version
-    and structure sizes.
-
-Version 1.0.7beta11 [May 7, 2000]
-  Removed the new PNG_CREATED_READ_STRUCT and PNG_CREATED_WRITE_STRUCT modes
-    which are no longer used.
-  Eliminated the three new members of png_text when PNG_LEGACY_SUPPORTED is
-    defined or when neither PNG_READ_iTXt_SUPPORTED nor PNG_WRITE_iTXt_SUPPORTED
-    is defined.
-  Made PNG_NO_READ|WRITE_iTXt the default setting, to avoid memory
-    overrun when old applications fill the info_ptr->text structure directly.
-  Added PNGAPI macro, and added it to the definitions of all exported functions.
-  Relocated version macro definitions ahead of the includes of zlib.h and
-    pngconf.h in png.h.
-
-Version 1.0.7beta12 [May 12, 2000]
-  Revised pngset.c to avoid a problem with expanding the png_debug macro.
-  Deleted some extraneous defines from pngconf.h
-  Made PNG_NO_CONSOLE_IO the default condition when PNG_BUILD_DLL is defined.
-  Use MSC _RPTn debugging instead of fprintf if _MSC_VER is defined.
-  Added png_access_version_number() function.
-  Check for mask&PNG_FREE_CHNK (for TEXT, SCAL, PCAL) in png_free_data().
-  Expanded libpng.3/libpng.txt information about png_data_freer().
-
-Version 1.0.7beta14 [May 17, 2000] (beta13 was not published)
-  Changed pnggccrd.c and pngvcrd.c to handle bad adaptive filter types as
-    warnings instead of errors, as pngrutil.c does.
-  Set the PNG_INFO_IDAT valid flag in png_set_rows() so png_write_png()
-    will actually write IDATs.
-  Made the default PNG_USE_LOCAL_ARRAYS depend on PNG_DLL instead of WIN32.
-  Make png_free_data() ignore its final parameter except when freeing data
-    that can have multiple instances (text, sPLT, unknowns).
-  Fixed a new bug in png_set_rows().
-  Removed info_ptr->valid tests from png_free_data(), as in version 1.0.5.
-  Added png_set_invalid() function.
-  Fixed incorrect illustrations of png_destroy_write_struct() in example.c.
-
-Version 1.0.7beta15 [May 30, 2000]
-  Revised the deliberately erroneous Linux setjmp code in pngconf.h to produce
-    fewer error messages.
-  Rearranged checks for Z_OK to check the most likely path first in pngpread.c
-    and pngwutil.c.
-  Added checks in pngtest.c for png_create_*() returning NULL, and mentioned
-    in libpng.txt/libpng.3 the need for applications to check this.
-  Changed names of png_default_*() functions in pngtest to pngtest_*().
-  Changed return type of png_get_x|y_offset_*() from png_uint_32 to png_int_32.
-  Fixed some bugs in the unused PNG_INCH_CONVERSIONS functions in pngget.c
-  Set each pointer to NULL after freeing it in png_free_data().
-  Worked around a problem in pngconf.h; AIX's strings.h defines an "index"
-    macro that conflicts with libpng's png_color_16.index. (Dimitri
-    Papadapoulos)
-  Added "msvc" directory with MSVC++ project files (Simon-Pierre Cadieux).
-
-Version 1.0.7beta16 [June 4, 2000]
-  Revised the workaround of AIX string.h "index" bug.
-  Added a check for overlength PLTE chunk in pngrutil.c.
-  Added PNG_NO_POINTER_INDEXING macro to use array-indexing instead of pointer
-    indexing in pngrutil.c and pngwutil.c to accommodate a buggy compiler.
-  Added a warning in png_decompress_chunk() when it runs out of data, e.g.
-    when it tries to read an erroneous PhotoShop iCCP chunk.
-  Added PNG_USE_DLL macro.
-  Revised the copyright/disclaimer/license notice.
-  Added contrib/msvctest directory
-
-Version 1.0.7rc1 [June 9, 2000]
-  Corrected the definition of PNG_TRANSFORM_INVERT_ALPHA  (0x0400 not 0x0200)
-  Added contrib/visupng directory (Willem van Schaik)
-
-Version 1.0.7beta18 [June 23, 2000]
-  Revised PNGAPI definition, and pngvcrd.c to work with __GCC__
-    and do not redefine PNGAPI if it is passed in via a compiler directive.
-  Revised visupng/PngFile.c to remove returns from within the Try block.
-  Removed leading underscores from "_PNG_H" and "_PNG_SAVE_BSD_SOURCE" macros.
-  Updated contrib/visupng/cexcept.h to version 1.0.0.
-  Fixed bugs in pngwrite.c and pngwutil.c that prevented writing iCCP chunks.
-
-Version 1.0.7rc2 [June 28, 2000]
-  Updated license to include disclaimers required by UCITA.
-  Fixed "DJBPP" typo in pnggccrd.c introduced in beta18.
-
-Version 1.0.7 [July 1, 2000]
-  Revised the definition of "trans_values" in libpng.3/libpng.txt
-
-Version 1.0.8beta1 [July 8, 2000]
-  Added png_free(png_ptr, key) two places in pngpread.c to stop memory leaks.
-  Changed PNG_NO_STDIO to PNG_NO_CONSOLE_IO, several places in pngrutil.c and
-    pngwutil.c.
-  Changed PNG_EXPORT_VAR to use PNG_IMPEXP, in pngconf.h.
-  Removed unused "#include <assert.h>" from png.c
-  Added WindowsCE support.
-  Revised pnggccrd.c to work with gcc-2.95.2 and in the Cygwin environment.
-
-Version 1.0.8beta2 [July 10, 2000]
-  Added project files to the wince directory and made further revisions
-    of pngtest.c, pngrio.c, and pngwio.c in support of WindowsCE.
-
-Version 1.0.8beta3 [July 11, 2000]
-  Only set the PNG_FLAG_FREE_TRNS or PNG_FREE_TRNS flag in png_handle_tRNS()
-    for indexed-color input files to avoid potential double-freeing trans array
-    under some unusual conditions; problem was introduced in version 1.0.6f.
-  Further revisions to pngtest.c and files in the wince subdirectory.
-
-Version 1.0.8beta4 [July 14, 2000]
-  Added the files pngbar.png and pngbar.jpg to the distribution.
-  Added makefile.cygwin, and cygwin support in pngconf.h
-  Added PNG_NO_ZALLOC_ZERO macro (makes png_zalloc skip zeroing memory)
-
-Version 1.0.8rc1 [July 16, 2000]
-  Revised png_debug() macros and statements to eliminate compiler warnings.
-
-Version 1.0.8 [July 24, 2000]
-  Added png_flush() in pngwrite.c, after png_write_IEND().
-  Updated makefile.hpux to build a shared library.
-
-Version 1.0.9beta1 [November 10, 2000]
-  Fixed typo in scripts/makefile.hpux
-  Updated makevms.com in scripts and contrib/* and contrib/* (Martin Zinser)
-  Fixed seqence-point bug in contrib/pngminus/png2pnm (Martin Zinser)
-  Changed "cdrom.com" in documentation to "libpng.org"
-  Revised pnggccrd.c to get it all working, and updated makefile.gcmmx (Greg).
-  Changed type of "params" from voidp to png_voidp in png_read|write_png().
-  Make sure PNGAPI and PNG_IMPEXP are defined in pngconf.h.
-  Revised the 3 instances of WRITEFILE in pngtest.c.
-  Relocated "msvc" and "wince" project subdirectories into "dll" subdirectory.
-  Updated png.rc in dll/msvc project
-  Revised makefile.dec to define and use LIBPATH and INCPATH
-  Increased size of global png_libpng_ver[] array from 12 to 18 chars.
-  Made global png_libpng_ver[], png_sig[] and png_pass_*[] arrays const.
-  Removed duplicate png_crc_finish() from png_handle_bKGD() function.
-  Added a warning when application calls png_read_update_info() multiple times.
-  Revised makefile.cygwin
-  Fixed bugs in iCCP support in pngrutil.c and pngwutil.c.
-  Replaced png_set_empty_plte_permitted() with png_permit_mng_features().
-
-Version 1.0.9beta2 [November 19, 2000]
-  Renamed the "dll" subdirectory "projects".
-  Added borland project files to "projects" subdirectory.
-  Set VS_FF_PRERELEASE and VS_FF_PATCHED flags in msvc/png.rc when appropriate.
-  Add error message in png_set_compression_buffer_size() when malloc fails.
-
-Version 1.0.9beta3 [November 23, 2000]
-  Revised PNG_LIBPNG_BUILD_TYPE macro in png.h, used in the msvc project.
-  Removed the png_flush() in pngwrite.c that crashes some applications
-    that don't set png_output_flush_fn.
-  Added makefile.macosx and makefile.aix to scripts directory.
-
-Version 1.0.9beta4 [December 1, 2000]
-  Change png_chunk_warning to png_warning in png_check_keyword().
-  Increased the first part of msg buffer from 16 to 18 in png_chunk_error().
-
-Version 1.0.9beta5 [December 15, 2000]
-  Added support for filter method 64 (for PNG datastreams embedded in MNG).
-
-Version 1.0.9beta6 [December 18, 2000]
-  Revised png_set_filter() to accept filter method 64 when appropriate.
-  Added new PNG_HAVE_PNG_SIGNATURE bit to png_ptr->mode and use it to
-    help prevent applications from using MNG features in PNG datastreams.
-  Added png_permit_mng_features() function.
-  Revised libpng.3/libpng.txt.  Changed "filter type" to "filter method".
-
-Version 1.0.9rc1 [December 23, 2000]
-  Revised test for PNG_HAVE_PNG_SIGNATURE in pngrutil.c
-  Fixed error handling of unknown compression type in png_decompress_chunk().
-  In pngconf.h, define __cdecl when _MSC_VER is defined.
-
-Version 1.0.9beta7 [December 28, 2000]
-  Changed PNG_TEXT_COMPRESSION_zTXt to PNG_COMPRESSION_TYPE_BASE several places.
-  Revised memory management in png_set_hIST and png_handle_hIST in a backward
-    compatible manner.  PLTE and tRNS were revised similarly.
-  Revised the iCCP chunk reader to ignore trailing garbage.
-
-Version 1.0.9beta8 [January 12, 2001]
-  Moved pngasmrd.h into pngconf.h.
-  Improved handling of out-of-spec garbage iCCP chunks generated by PhotoShop.
-
-Version 1.0.9beta9 [January 15, 2001]
-  Added png_set_invalid, png_permit_mng_features, and png_mmx_supported to
-    wince and msvc project module definition files.
-  Minor revision of makefile.cygwin.
-  Fixed bug with progressive reading of narrow interlaced images in pngpread.c
-
-Version 1.0.9beta10 [January 16, 2001]
-  Do not typedef png_FILE_p in pngconf.h when PNG_NO_STDIO is defined.
-  Fixed "png_mmx_supported" typo in project definition files.
-
-Version 1.0.9beta11 [January 19, 2001]
-  Updated makefile.sgi to make shared library.
-  Removed png_mmx_support() function and disabled PNG_MNG_FEATURES_SUPPORTED
-    by default, for the benefit of DLL forward compatibility.  These will
-    be re-enabled in version 1.2.0.
-
-Version 1.0.9rc2 [January 22, 2001]
-  Revised cygwin support.
-
-Version 1.0.9 [January 31, 2001]
-  Added check of cygwin's ALL_STATIC in pngconf.h
-  Added "-nommx" parameter to contrib/gregbook/rpng2-win and rpng2-x demos.
-
-Version 1.0.10beta1 [March 14, 2001]
-  Revised makefile.dec, makefile.sgi, and makefile.sggcc; added makefile.hpgcc.
-  Reformatted libpng.3 to eliminate bad line breaks.
-  Added checks for _mmx_supported in the read_filter_row function of pnggccrd.c
-  Added prototype for png_mmx_support() near the top of pnggccrd.c
-  Moved some error checking from png_handle_IHDR to png_set_IHDR.
-  Added PNG_NO_READ_SUPPORTED and PNG_NO_WRITE_SUPPORTED macros.
-  Revised png_mmx_support() function in pnggccrd.c
-  Restored version 1.0.8 PNG_WRITE_EMPTY_PLTE_SUPPORTED behavior in pngwutil.c
-  Fixed memory leak in contrib/visupng/PngFile.c
-  Fixed bugs in png_combine_row() in pnggccrd.c and pngvcrd.c (C version)
-  Added warnings when retrieving or setting gamma=0.
-  Increased the first part of msg buffer from 16 to 18 in png_chunk_warning().
-
-Version 1.0.10rc1 [March 23, 2001]
-  Changed all instances of memcpy, strcpy, and strlen to png_memcpy, png_strcpy,
-    and png_strlen.
-  Revised png_mmx_supported() function in pnggccrd.c to return proper value.
-  Fixed bug in progressive reading (pngpread.c) with small images (height < 8).
-
-Version 1.0.10 [March 30, 2001]
-  Deleted extraneous space (introduced in 1.0.9) from line 42 of makefile.cygwin
-  Added beos project files (Chris Herborth)
-
-Version 1.0.11beta1 [April 3, 2001]
-  Added type casts on several png_malloc() calls (Dimitri Papadapoulos).
-  Removed a no-longer needed AIX work-around from pngconf.h
-  Changed several "//" single-line comments to C-style in pnggccrd.c
-
-Version 1.0.11beta2 [April 11, 2001]
-  Removed PNGAPI from several functions whose prototypes did not have PNGAPI.
-  Updated scripts/pngos2.def
-
-Version 1.0.11beta3 [April 14, 2001]
-  Added checking the results of many instances of png_malloc() for NULL
-
-Version 1.0.11beta4 [April 20, 2001]
-  Undid the changes from version 1.0.11beta3.  Added a check for NULL return
-    from user's malloc_fn().
-  Removed some useless type casts of the NULL pointer.
-  Added makefile.netbsd
-
-Version 1.0.11 [April 27, 2001]
-  Revised makefile.netbsd
-
-Version 1.0.12beta1 [May 14, 2001]
-  Test for Windows platform in pngconf.h when including malloc.h (Emmanuel Blot)
-  Updated makefile.cygwin and handling of Cygwin's ALL_STATIC in pngconf.h
-  Added some never-to-be-executed code in pnggccrd.c to quiet compiler warnings.
-  Eliminated the png_error about apps using png_read|write_init().  Instead,
-    libpng will reallocate the png_struct and info_struct if they are too small.
-    This retains future binary compatibility for old applications written for
-    libpng-0.88 and earlier.
-
-Version 1.2.0beta1 [May 6, 2001]
-  Bumped DLLNUM to 2.
-  Re-enabled PNG_MNG_FEATURES_SUPPORTED and enabled PNG_ASSEMBLER_CODE_SUPPORTED
-    by default.
-  Added runtime selection of MMX features.
-  Added png_set_strip_error_numbers function and related macros.
-
-Version 1.2.0beta2 [May 7, 2001]
-  Finished merging 1.2.0beta1 with version 1.0.11
-  Added a check for attempts to read or write PLTE in grayscale PNG datastreams.
-
-Version 1.2.0beta3 [May 17, 2001]
-  Enabled user memory function by default.
-  Modified png_create_struct so it passes user mem_ptr to user memory allocator.
-  Increased png_mng_features flag from png_byte to png_uint_32.
-  Bumped shared-library (so-number) and dll-number to 3.
-
-Version 1.2.0beta4 [June 23, 2001]
-  Check for missing profile length field in iCCP chunk and free chunk_data
-    in case of truncated iCCP chunk.
-  Bumped shared-library number to 3 in makefile.sgi and makefile.sggcc
-  Bumped dll-number from 2 to 3 in makefile.cygwin
-  Revised contrib/gregbook/rpng*-x.c to avoid a memory leak and to exit cleanly
-    if user attempts to run it on an 8-bit display.
-  Updated contrib/gregbook
-  Use png_malloc instead of png_zalloc to allocate palette in pngset.c
-  Updated makefile.ibmc
-  Added some typecasts to eliminate gcc 3.0 warnings.  Changed prototypes
-    of png_write_oFFS width and height from png_uint_32 to png_int_32.
-  Updated example.c
-  Revised prototypes for png_debug_malloc and png_debug_free in pngtest.c
-
-Version 1.2.0beta5 [August 8, 2001]
-  Revised contrib/gregbook
-  Revised makefile.gcmmx
-  Revised pnggccrd.c to conditionally compile some thread-unsafe code only
-    when PNG_THREAD_UNSAFE_OK is defined.
-  Added tests to prevent pngwutil.c from writing a bKGD or tRNS chunk with
-    value exceeding 2^bit_depth-1
-  Revised makefile.sgi and makefile.sggcc
-  Replaced calls to fprintf(stderr,...) with png_warning() in pnggccrd.c
-  Removed restriction that do_invert_mono only operate on 1-bit opaque files
-
-Version 1.2.0 [September 1, 2001]
-  Changed a png_warning() to png_debug() in pnggccrd.c
-  Fixed contrib/gregbook/rpng-x.c, rpng2-x.c to avoid crash with XFreeGC().
-
-Version 1.2.1beta1 [October 19, 2001]
-  Revised makefile.std in contrib/pngminus
-  Include background_1 in png_struct regardless of gamma support.
-  Revised makefile.netbsd and makefile.macosx, added makefile.darwin.
-  Revised example.c to provide more details about using row_callback().
-
-Version 1.2.1beta2 [October 25, 2001]
-  Added type cast to each NULL appearing in a function call, except for
-    WINCE functions.
-  Added makefile.so9.
-
-Version 1.2.1beta3 [October 27, 2001]
-  Removed type casts from all NULLs.
-  Simplified png_create_struct_2().
-
-Version 1.2.1beta4 [November 7, 2001]
-  Revised png_create_info_struct() and png_creat_struct_2().
-  Added error message if png_write_info() was omitted.
-  Type cast NULLs appearing in function calls when _NO_PROTO or
-    PNG_TYPECAST_NULL is defined.
-
-Version 1.2.1rc1 [November 24, 2001]
-  Type cast NULLs appearing in function calls except when PNG_NO_TYPECAST_NULL
-    is defined.
-  Changed typecast of "size" argument to png_size_t in pngmem.c calls to
-    the user malloc_fn, to agree with the prototype in png.h
-  Added a pop/push operation to pnggccrd.c, to preserve Eflag (Maxim Sobolev)
-  Updated makefile.sgi to recognize LIBPATH and INCPATH.
-  Updated various makefiles so "make clean" does not remove previous major
-    version of the shared library.
-
-Version 1.2.1rc2 [December 4, 2001]
-  Always allocate 256-entry internal palette, hist, and trans arrays, to
-    avoid out-of-bounds memory reference caused by invalid PNG datastreams.
-  Added a check for prefix_length > data_length in iCCP chunk handler.
-
-Version 1.2.1 [December 7, 2001]
-  None.
-
-Version 1.2.2beta1 [February 22, 2002]
-  Fixed a bug with reading the length of iCCP profiles (Larry Reeves).
-  Revised makefile.linux, makefile.gcmmx, and makefile.sgi to generate
-    libpng.a, libpng12.so (not libpng.so.3), and libpng12/png.h
-  Revised makefile.darwin to remove "-undefined suppress" option.
-  Added checks for gamma and chromaticity values over 21474.83, which exceed
-    the limit for PNG unsigned 32-bit integers when encoded.
-  Revised calls to png_create_read_struct() and png_create_write_struct()
-    for simpler debugging.
-  Revised png_zalloc() so zlib handles errors (uses PNG_FLAG_MALLOC_NULL_MEM_OK)
-
-Version 1.2.2beta2 [February 23, 2002]
-  Check chunk_length and idat_size for invalid (over PNG_MAX_UINT) lengths.
-  Check for invalid image dimensions in png_get_IHDR.
-  Added missing "fi;" in the install target of the SGI makefiles.
-  Added install-static to all makefiles that make shared libraries.
-  Always do gamma compensation when image is partially transparent.
-
-Version 1.2.2beta3 [March 7, 2002]
-  Compute background.gray and background_1.gray even when color_type is RGB
-    in case image gets reduced to gray later.
-  Modified shared-library makefiles to install pkgconfig/libpngNN.pc.
-  Export (with PNGAPI) png_zalloc, png_zfree, and png_handle_as_unknown
-  Removed unused png_write_destroy_info prototype from png.h
-  Eliminated incorrect use of width_mmx from pnggccrd.c in pixel_bytes == 8 case
-  Added install-shared target to all makefiles that make shared libraries.
-  Stopped a double free of palette, hist, and trans when not using free_me.
-  Added makefile.32sunu for Sun Ultra 32 and makefile.64sunu for Sun Ultra 64.
-
-Version 1.2.2beta4 [March 8, 2002]
-  Compute background.gray and background_1.gray even when color_type is RGB
-    in case image gets reduced to gray later (Jason Summers).
-  Relocated a misplaced /bin/rm in the "install-shared" makefile targets
-  Added PNG_1_0_X macro which can be used to build a 1.0.x-compatible library.
-
-Version 1.2.2beta5 [March 26, 2002]
-  Added missing PNGAPI to several function definitions.
-  Check for invalid bit_depth or color_type in png_get_IHDR(), and
-    check for missing PLTE or IHDR in png_push_read_chunk() (Matthias Clasen).
-  Revised iTXt support to accept NULL for lang and lang_key.
-  Compute gamma for color components of background even when color_type is gray.
-  Changed "()" to "{}" in scripts/libpng.pc.in.
-  Revised makefiles to put png.h and pngconf.h only in $prefix/include/libpngNN
-  Revised makefiles to make symlink to libpng.so.NN in addition to libpngNN.so
-
-Version 1.2.2beta6 [March 31, 2002]
-
-Version 1.0.13beta1 [March 31, 2002]
-  Prevent png_zalloc() from trying to memset memory that it failed to acquire.
-  Add typecasts of PNG_MAX_UINT in pngset_cHRM_fixed() (Matt Holgate).
-  Ensure that the right function (user or default) is used to free the
-    png_struct after an error in png_create_read_struct_2().
-
-Version 1.2.2rc1 [April 7, 2002]
-
-Version 1.0.13rc1 [April 7, 2002]
-  Save the ebx register in pnggccrd.c (Sami Farin)
-  Add "mem_ptr = png_ptr->mem_ptr" in png_destroy_write_struct() (Paul Gardner).
-  Updated makefiles to put headers in include/libpng and remove old include/*.h.
-
-Version 1.2.2 [April 15, 2002]
-
-Version 1.0.13 [April 15, 2002]
-  Revised description of png_set_filter() in libpng.3/libpng.txt.
-  Revised makefile.netbsd and added makefile.neNNbsd and makefile.freebsd
-
-Version 1.0.13patch01 [April 17, 2002]
-
-Version 1.2.2patch01 [April 17, 2002]
-  Changed ${PNGMAJ}.${PNGVER} bug to ${PNGVER} in makefile.sgi and
-    makefile.sggcc
-  Fixed VER -> PNGVER typo in makefile.macosx and added install-static to
-    install
-  Added install: target to makefile.32sunu and makefile.64sunu
-
-Version 1.0.13patch03 [April 18, 2002]
-
-Version 1.2.2patch03 [April 18, 2002]
-  Revised 15 makefiles to link libpng.a to libpngNN.a and the include libpng
-  subdirectory to libpngNN subdirectory without the full pathname.
-  Moved generation of libpng.pc from "install" to "all" in 15 makefiles.
-
-Version 1.2.3rc1 [April 28, 2002]
-  Added install-man target to 15 makefiles (Dimitri Papadopolous-Orfanos).
-  Added $(DESTDIR) feature to 24 makefiles (Tim Mooney)
-  Fixed bug with $prefix, should be $(prefix) in makefile.hpux.
-  Updated cygwin-specific portion of pngconf.h and revised makefile.cygwin
-  Added a link from libpngNN.pc to libpng.pc in 15 makefiles.
-  Added links from include/libpngNN/*.h to include/*.h in 24 makefiles.
-  Revised makefile.darwin to make relative links without full pathname.
-  Added setjmp() at the end of png_create_*_struct_2() in case user forgets
-    to put one in their application.
-  Restored png_zalloc() and png_zfree() prototypes to version 1.2.1 and
-    removed them from module definition files.
-
-Version 1.2.3rc2 [May 1, 2002]
-  Fixed bug in reporting number of channels in pngget.c and pngset.c,
-    that was introduced in version 1.2.2beta5.
-  Exported png_zalloc(), png_zfree(), png_default_read(), png_default_write(),
-    png_default_flush(), and png_push_fill_buffer() and included them in
-    module definition files.
-  Added "libpng.pc" dependency to the "install-shared" target in 15 makefiles.
-
-Version 1.2.3rc3 [May 1, 2002]
-  Revised prototype for png_default_flush()
-  Remove old libpng.pc and libpngNN.pc before installing new ones.
-
-Version 1.2.3rc4 [May 2, 2002]
-  Typos in *.def files (png_default_read|write -> png_default_read|write_data)
-  In makefiles, changed rm libpng.NN.pc to rm libpngNN.pc
-  Added libpng-config and libpngNN-config and modified makefiles to install
-    them.
-  Changed $(MANPATH) to $(DESTDIR)$(MANPATH) in makefiles
-  Added "Win32 DLL VB" configuration to projects/msvc/libpng.dsp
-
-Version 1.2.3rc5 [May 11, 2002]
-  Changed "error" and "message" in prototypes to "error_message" and
-    "warning_message" to avoid namespace conflict.
-  Revised 15 makefiles to build libpng-config from libpng-config-*.in
-  Once more restored png_zalloc and png_zfree to regular nonexported form.
-  Restored png_default_read|write_data, png_default_flush, png_read_fill_buffer
-    to nonexported form, but with PNGAPI, and removed them from module def
-    files.
-
-Version 1.2.3rc6 [May 14, 2002]
-  Removed "PNGAPI" from png_zalloc() and png_zfree() in png.c
-  Changed "Gz" to "Gd" in projects/msvc/libpng.dsp and zlib.dsp.
-  Removed leftover libpng-config "sed" script from four makefiles.
-  Revised libpng-config creating script in 16 makefiles.
-
-Version 1.2.3 [May 22, 2002]
-  Revised libpng-config target in makefile.cygwin.
-  Removed description of png_set_mem_fn() from documentation.
-  Revised makefile.freebsd.
-  Minor cosmetic changes to 15 makefiles, e.g., $(DI) = $(DESTDIR)/$(INCDIR).
-  Revised projects/msvc/README.txt
-  Changed -lpng to -lpngNN in LDFLAGS in several makefiles.
-
-Version 1.2.4beta1 [May 24, 2002]
-  Added libpng.pc and libpng-config to "all:" target in 16 makefiles.
-  Fixed bug in 16 makefiles: $(DESTDIR)/$(LIBPATH) to $(DESTDIR)$(LIBPATH)
-  Added missing "\" before closing double quote in makefile.gcmmx.
-  Plugged various memory leaks; added png_malloc_warn() and png_set_text_2()
-    functions.
-
-Version 1.2.4beta2 [June 25, 2002]
-  Plugged memory leak of png_ptr->current_text (Matt Holgate).
-  Check for buffer overflow before reading CRC in pngpread.c (Warwick Allison)
-  Added -soname to the loader flags in makefile.dec, makefile.sgi, and
-    makefile.sggcc.
-  Added "test-installed" target to makefile.linux, makefile.gcmmx,
-    makefile.sgi, and makefile.sggcc.
-
-Version 1.2.4beta3 [June 28, 2002]
-  Plugged memory leak of row_buf in pngtest.c when there is a png_error().
-  Detect buffer overflow in pngpread.c when IDAT is corrupted with extra data.
-  Added "test-installed" target to makefile.32sunu, makefile.64sunu,
-    makefile.beos, makefile.darwin, makefile.dec, makefile.macosx,
-    makefile.solaris, makefile.hpux, makefile.hpgcc, and makefile.so9.
-
-Version 1.2.4rc1 and 1.0.14rc1 [July 2, 2002]
-  Added "test-installed" target to makefile.cygwin and makefile.sco.
-  Revised pnggccrd.c to be able to back out version 1.0.x via PNG_1_0_X macro.
-
-Version 1.2.4 and 1.0.14 [July 8, 2002]
-  Changed png_warning() to png_error() when width is too large to process.
-
-Version 1.2.4patch01 [July 20, 2002]
-  Revised makefile.cygwin to use DLL number 12 instead of 13.
-
-Version 1.2.5beta1 [August 6, 2002]
-  Added code to contrib/gregbook/readpng2.c to ignore unused chunks.
-  Replaced toucan.png in contrib/gregbook (it has been corrupt since 1.0.11)
-  Removed some stray *.o files from contrib/gregbook.
-  Changed png_error() to png_warning() about "Too much data" in pngpread.c
-    and about "Extra compressed data" in pngrutil.c.
-  Prevent png_ptr->pass from exceeding 7 in png_push_finish_row().
-  Updated makefile.hpgcc
-  Updated png.c and pnggccrd.c handling of return from png_mmx_support()
-
-Version 1.2.5beta2 [August 15, 2002]
-  Only issue png_warning() about "Too much data" in pngpread.c when avail_in
-    is nonzero.
-  Updated makefiles to install a separate libpng.so.3 with its own rpath.
-
-Version 1.2.5rc1 and 1.0.15rc1 [August 24, 2002]
-  Revised makefiles to not remove previous minor versions of shared libraries.
-
-Version 1.2.5rc2 and 1.0.15rc2 [September 16, 2002]
-  Revised 13 makefiles to remove "-lz" and "-L$(ZLIBLIB)", etc., from shared
-    library loader directive.
-  Added missing "$OBJSDLL" line to makefile.gcmmx.
-  Added missing "; fi" to makefile.32sunu.
-
-Version 1.2.5rc3 and 1.0.15rc3 [September 18, 2002]
-  Revised libpng-config script.
-
-Version 1.2.5 and 1.0.15 [October 3, 2002]
-  Revised makefile.macosx, makefile.darwin, makefile.hpgcc, and makefile.hpux,
-    and makefile.aix.
-  Relocated two misplaced PNGAPI lines in pngtest.c
-
-Version 1.2.6beta1 [October 22, 2002]
-  Commented out warning about uninitialized mmx_support in pnggccrd.c.
-  Changed "IBMCPP__" flag to "__IBMCPP__" in pngconf.h.
-  Relocated two more misplaced PNGAPI lines in pngtest.c
-  Fixed memory overrun bug in png_do_read_filler() with 16-bit datastreams,
-    introduced in version 1.0.2.
-  Revised makefile.macosx, makefile.dec, makefile.aix, and makefile.32sunu.
-
-Version 1.2.6beta2 [November 1, 2002]
-  Added libpng-config "--ldopts" output.
-  Added "AR=ar" and "ARFLAGS=rc" and changed "ar rc" to "$(AR) $(ARFLAGS)"
-    in makefiles.
-
-Version 1.2.6beta3 [July 18, 2004]
-  Reverted makefile changes from version 1.2.6beta2 and some of the changes
-    from version 1.2.6beta1; these will be postponed until version 1.2.7.
-    Version 1.2.6 is going to be a simple bugfix release.
-  Changed the one instance of "ln -sf" to "ln -f -s" in each Sun makefile.
-  Fixed potential overrun in pngerror.c by using strncpy instead of memcpy.
-  Added "#!/bin/sh" at the top of configure, for recognition of the
-    'x' flag under Cygwin (Cosmin).
-  Optimized vacuous tests that silence compiler warnings, in png.c (Cosmin).
-  Added support for PNG_USER_CONFIG, in pngconf.h (Cosmin).
-  Fixed the special memory handler for Borland C under DOS, in pngmem.c
-    (Cosmin).
-  Removed some spurious assignments in pngrutil.c (Cosmin).
-  Replaced 65536 with 65536L, and 0xffff with 0xffffL, to silence warnings
-    on 16-bit platforms (Cosmin).
-  Enclosed shift op expressions in parentheses, to silence warnings (Cosmin).
-  Used proper type png_fixed_point, to avoid problems on 16-bit platforms,
-    in png_handle_sRGB() (Cosmin).
-  Added compression_type to png_struct, and optimized the window size
-    inside the deflate stream (Cosmin).
-  Fixed definition of isnonalpha(), in pngerror.c and pngrutil.c (Cosmin).
-  Fixed handling of unknown chunks that come after IDAT (Cosmin).
-  Allowed png_error() and png_warning() to work even if png_ptr == NULL
-    (Cosmin).
-  Replaced row_info->rowbytes with row_bytes in png_write_find_filter()
-    (Cosmin).
-  Fixed definition of PNG_LIBPNG_VER_DLLNUM (Simon-Pierre).
-  Used PNG_LIBPNG_VER and PNG_LIBPNG_VER_STRING instead of the hardcoded
-    values in png.c (Simon-Pierre, Cosmin).
-  Initialized png_libpng_ver[] with PNG_LIBPNG_VER_STRING (Simon-Pierre).
-  Replaced PNG_LIBPNG_VER_MAJOR with PNG_LIBPNG_VER_DLLNUM in png.rc
-    (Simon-Pierre).
-  Moved the definition of PNG_HEADER_VERSION_STRING near the definitions
-    of the other PNG_LIBPNG_VER_... symbols in png.h (Cosmin).
-  Relocated #ifndef PNGAPI guards in pngconf.h (Simon-Pierre, Cosmin).
-  Updated scripts/makefile.vc(a)win32 (Cosmin).
-  Updated the MSVC project (Simon-Pierre, Cosmin).
-  Updated the Borland C++ Builder project (Cosmin).
-  Avoided access to asm_flags in pngvcrd.c, if PNG_1_0_X is defined (Cosmin).
-  Commented out warning about uninitialized mmx_support in pngvcrd.c (Cosmin).
-  Removed scripts/makefile.bd32 and scripts/pngdef.pas (Cosmin).
-  Added extra guard around inclusion of Turbo C memory headers, in pngconf.h
-    (Cosmin).
-  Renamed projects/msvc/ to projects/visualc6/, and projects/borland/ to
-    projects/cbuilder5/ (Cosmin).
-  Moved projects/visualc6/png32ms.def to scripts/pngw32.def,
-    and projects/visualc6/png.rc to scripts/pngw32.rc (Cosmin).
-  Added projects/visualc6/pngtest.dsp; removed contrib/msvctest/ (Cosmin).
-  Changed line endings to DOS style in cbuilder5 and visualc6 files, even
-    in the tar.* distributions (Cosmin).
-  Updated contrib/visupng/VisualPng.dsp (Cosmin).
-  Updated contrib/visupng/cexcept.h to version 2.0.0 (Cosmin).
-  Added a separate distribution with "configure" and supporting files (Junichi).
-
-Version 1.2.6beta4 [July 28, 2004]
-  Added user ability to change png_size_t via a PNG_SIZE_T macro.
-  Added png_sizeof() and png_convert_size() functions.
-  Added PNG_SIZE_MAX (maximum value of a png_size_t variable.
-  Added check in png_malloc_default() for (size_t)size != (png_uint_32)size
-    which would indicate an overflow.
-  Changed sPLT failure action from png_error to png_warning and abandon chunk.
-  Changed sCAL and iCCP failures from png_error to png_warning and abandon.
-  Added png_get_uint_31(png_ptr, buf) function.
-  Added PNG_UINT_32_MAX macro.
-  Renamed PNG_MAX_UINT to PNG_UINT_31_MAX.
-  Made png_zalloc() issue a png_warning and return NULL on potential
-    overflow.
-  Turn on PNG_NO_ZALLOC_ZERO by default in version 1.2.x
-  Revised "clobber list" in pnggccrd.c so it will compile under gcc-3.4.
-  Revised Borland portion of png_malloc() to return NULL or issue
-    png_error() according to setting of PNG_FLAG_MALLOC_NULL_MEM_OK.
-  Added PNG_NO_SEQUENTIAL_READ_SUPPORTED macro to conditionally remove
-    sequential read support.
-  Added some "#if PNG_WRITE_SUPPORTED" blocks.
-  Added #ifdef to remove some redundancy in png_malloc_default().
-  Use png_malloc instead of png_zalloc to allocate the pallete.
-
-Version 1.0.16rc1 and 1.2.6rc1 [August 4, 2004]
-  Fixed buffer overflow vulnerability (CVE-2004-0597) in png_handle_tRNS().
-  Fixed NULL dereference vulnerability (CVE-2004-0598) in png_handle_iCCP().
-  Fixed integer overflow vulnerability (CVE-2004-0599) in png_read_png().
-  Fixed some harmless bugs in png_handle_sBIT, etc, that would cause
-    duplicate chunk types to go undetected.
-  Fixed some timestamps in the -config version
-  Rearranged order of processing of color types in png_handle_tRNS().
-  Added ROWBYTES macro to calculate rowbytes without integer overflow.
-  Updated makefile.darwin and removed makefile.macosx from scripts directory.
-  Imposed default one million column, one-million row limits on the image
-    dimensions, and added png_set_user_limits() function to override them.
-  Revised use of PNG_SET_USER_LIMITS_SUPPORTED macro.
-  Fixed wrong cast of returns from png_get_user_width|height_max().
-  Changed some "keep the compiler happy" from empty statements to returns,
-  Revised libpng.txt to remove 1.2.x stuff from the 1.0.x distribution
-
-Version 1.0.16rc2 and 1.2.6rc2 [August 7, 2004]
-  Revised makefile.darwin and makefile.solaris.  Removed makefile.macosx.
-  Revised pngtest's png_debug_malloc() to use png_malloc() instead of
-    png_malloc_default() which is not supposed to be exported.
-  Fixed off-by-one error in one of the conversions to PNG_ROWBYTES() in
-    pngpread.c.  Bug was introduced in 1.2.6rc1.
-  Fixed bug in RGB to RGBX transformation introduced in 1.2.6rc1.
-  Fixed old bug in RGB to Gray transformation.
-  Fixed problem with 64-bit compilers by casting arguments to abs()
-    to png_int_32.
-  Changed "ln -sf" to "ln -f -s" in three makefiles (solaris, sco, so9).
-  Changed "HANDLE_CHUNK_*" to "PNG_HANDLE_CHUNK_*" (Cosmin)
-  Added "-@/bin/rm -f $(DL)/$(LIBNAME).so.$(PNGMAJ)" to 15 *NIX makefiles.
-  Added code to update the row_info->colortype in png_do_read_filler() (MSB).
-
-Version 1.0.16rc3 and 1.2.6rc3 [August 9, 2004]
-  Eliminated use of "abs()" in testing cHRM and gAMA values, to avoid
-    trouble with some 64-bit compilers.  Created PNG_OUT_OF_RANGE() macro.
-  Revised documentation of png_set_keep_unknown_chunks().
-  Check handle_as_unknown status in pngpread.c, as in pngread.c previously.
-  Moved  "PNG_HANDLE_CHUNK_*" macros out of PNG_INTERNAL section of png.h
-  Added "rim" definitions for CONST4 and CONST6 in pnggccrd.c
-
-Version 1.0.16rc4 and 1.2.6rc4 [August 10, 2004]
-  Fixed mistake in pngtest.c introduced in 1.2.6rc2 (declaration of
-    "pinfo" was out of place).
-
-Version 1.0.16rc5 and 1.2.6rc5 [August 10, 2004]
-  Moved  "PNG_HANDLE_CHUNK_*" macros out of PNG_ASSEMBLER_CODE_SUPPORTED
-    section of png.h where they were inadvertently placed in version rc3.
-
-Version 1.2.6 and 1.0.16 [August 15, 2004]
-  Revised pngtest so memory allocation testing is only done when PNG_DEBUG==1.
-
-Version 1.2.7beta1 [August 26, 2004]
-  Removed unused pngasmrd.h file.
-  Removed references to uu.net for archived files.  Added references to
-    PNG Spec (second edition) and the PNG ISO/IEC Standard.
-  Added "test-dd" target in 15 makefiles, to run pngtest in DESTDIR.
-  Fixed bug with "optimized window size" in the IDAT datastream, that
-    causes libpng to write PNG files with incorrect zlib header bytes.
-
-Version 1.2.7beta2 [August 28, 2004]
-  Fixed bug with sCAL chunk and big-endian machines (David Munro).
-  Undid new code added in 1.2.6rc2 to update the color_type in
-    png_set_filler().
-  Added png_set_add_alpha() that updates color type.
-
-Version 1.0.17rc1 and 1.2.7rc1 [September 4, 2004]
-  Revised png_set_strip_filler() to not remove alpha if color_type has alpha.
-
-Version 1.2.7 and 1.0.17 [September 12, 2004]
-  Added makefile.hp64
-  Changed projects/msvc/png32ms.def to scripts/png32ms.def in makefile.cygwin
-
-Version 1.2.8beta1 [November 1, 2004]
-  Fixed bug in png_text_compress() that would fail to complete a large block.
-  Fixed bug, introduced in libpng-1.2.7, that overruns a buffer during
-    strip alpha operation in png_do_strip_filler().
-  Added PNG_1_2_X definition in pngconf.h
-  Use #ifdef to comment out png_info_init in png.c and png_read_init in
-    pngread.c (as of 1.3.0)
-
-Version 1.2.8beta2 [November 2, 2004]
-  Reduce color_type to a nonalpha type after strip alpha operation in
-    png_do_strip_filler().
-
-Version 1.2.8beta3 [November 3, 2004]
-  Revised definitions of PNG_MAX_UINT_32, PNG_MAX_SIZE, and PNG_MAXSUM
-
-Version 1.2.8beta4 [November 12, 2004]
-  Fixed (again) definition of PNG_LIBPNG_VER_DLLNUM in png.h (Cosmin).
-  Added PNG_LIBPNG_BUILD_PRIVATE in png.h (Cosmin).
-  Set png_ptr->zstream.data_type to Z_BINARY, to avoid unnecessary detection
-    of data type in deflate (Cosmin).
-  Deprecated but continue to support SPECIALBUILD and PRIVATEBUILD in favor of
-    PNG_LIBPNG_BUILD_SPECIAL_STRING and PNG_LIBPNG_BUILD_PRIVATE_STRING.
-
-Version 1.2.8beta5 [November 20, 2004]
-  Use png_ptr->flags instead of png_ptr->transformations to pass
-    PNG_STRIP_ALPHA info to png_do_strip_filler(), to preserve ABI
-    compatibility.
-  Revised handling of SPECIALBUILD, PRIVATEBUILD,
-    PNG_LIBPNG_BUILD_SPECIAL_STRING and PNG_LIBPNG_BUILD_PRIVATE_STRING.
-
-Version 1.2.8rc1 [November 24, 2004]
-  Moved handling of BUILD macros from pngconf.h to png.h
-  Added definition of PNG_LIBPNG_BASE_TYPE in png.h, inadvertently
-    omitted from beta5.
-  Revised scripts/pngw32.rc
-  Despammed mailing addresses by masking "@" with "at".
-  Inadvertently installed a supposedly faster test version of pngrutil.c
-
-Version 1.2.8rc2 [November 26, 2004]
-  Added two missing "\" in png.h
-  Change tests in pngread.c and pngpread.c to
-    if (png_ptr->transformations || (png_ptr->flags&PNG_FLAG_STRIP_ALPHA))
-       png_do_read_transformations(png_ptr);
-
-Version 1.2.8rc3 [November 28, 2004]
-  Reverted pngrutil.c to version libpng-1.2.8beta5.
-  Added scripts/makefile.elf with supporting code in pngconf.h for symbol
-    versioning (John Bowler).
-
-Version 1.2.8rc4 [November 29, 2004]
-  Added projects/visualc7 (Simon-pierre).
-
-Version 1.2.8rc5 [November 29, 2004]
-  Fixed new typo in scripts/pngw32.rc
-
-Version 1.2.8 [December 3, 2004]
-  Removed projects/visualc7, added projects/visualc71.
-
-Version 1.2.9beta1 [February 21, 2006]
-  Initialized some structure members in pngwutil.c to avoid gcc-4.0.0 complaints
-  Revised man page and libpng.txt to make it clear that one should not call
-    png_read_end or png_write_end after png_read_png or png_write_png.
-  Updated references to png-mng-implement mailing list.
-  Fixed an incorrect typecast in pngrutil.c
-  Added PNG_NO_READ_SUPPORTED conditional for making a write-only library.
-  Added PNG_NO_WRITE_INTERLACING_SUPPORTED conditional.
-  Optimized alpha-inversion loops in pngwtran.c
-  Moved test for nonzero gamma outside of png_build_gamma_table() in pngrtran.c
-  Make sure num_trans is <= 256 before copying data in png_set_tRNS().
-  Make sure num_palette is <= 256 before copying data in png_set_PLTE().
-  Interchanged order of write_swap_alpha and write_invert_alpha transforms.
-  Added parentheses in the definition of PNG_LIBPNG_BUILD_TYPE (Cosmin).
-  Optimized zlib window flag (CINFO) in contrib/pngsuite/*.png (Cosmin).
-  Updated scripts/makefile.bc32 for Borland C++ 5.6 (Cosmin).
-  Exported png_get_uint_32, png_save_uint_32, png_get_uint_16, png_save_uint_16,
-    png_get_int_32, png_save_int_32, png_get_uint_31 (Cosmin).
-  Added type cast (png_byte) in png_write_sCAL() (Cosmin).
-  Fixed scripts/makefile.cygwin (Christian Biesinger, Cosmin).
-  Default iTXt support was inadvertently enabled.
-
-Version 1.2.9beta2 [February 21, 2006]
-  Check for png_rgb_to_gray and png_gray_to_rgb read transformations before
-    checking for png_read_dither in pngrtran.c
-  Revised checking of chromaticity limits to accommodate extended RGB
-    colorspace (John Denker).
-  Changed line endings in some of the project files to CRLF, even in the
-    "Unix" tar distributions (Cosmin).
-  Made png_get_int_32 and png_save_int_32 always available (Cosmin).
-  Updated scripts/pngos2.def, scripts/pngw32.def and projects/wince/png32ce.def
-    with the newly exported functions.
-  Eliminated distributions without the "configure" script.
-  Updated INSTALL instructions.
-
-Version 1.2.9beta3 [February 24, 2006]
-  Fixed CRCRLF line endings in contrib/visupng/VisualPng.dsp
-  Made libpng.pc respect EXEC_PREFIX (D. P. Kreil, J. Bowler)
-  Removed reference to pngasmrd.h from Makefile.am
-  Renamed CHANGES to ChangeLog.
-  Renamed LICENSE to COPYING.
-  Renamed ANNOUNCE to NEWS.
-  Created AUTHORS file.
-
-Version 1.2.9beta4 [March 3, 2006]
-  Changed definition of PKGCONFIG from $prefix/lib to $libdir in configure.ac
-  Reverted to filenames LICENSE and ANNOUNCE; removed AUTHORS and COPYING.
-  Removed newline from the end of some error and warning messages.
-  Removed test for sqrt() from configure.ac and configure.
-  Made swap tables in pngtrans.c PNG_CONST (Carlo Bramix).
-  Disabled default iTXt support that was inadvertently enabled in
-    libpng-1.2.9beta1.
-  Added "OS2" to list of systems that don't need underscores, in pnggccrd.c
-  Removed libpng version and date from *.c files.
-
-Version 1.2.9beta5 [March 4, 2006]
-  Removed trailing blanks from source files.
-  Put version and date of latest change in each source file, and changed
-    copyright year accordingly.
-  More cleanup of configure.ac, Makefile.am, and associated scripts.
-  Restored scripts/makefile.elf which was inadvertently deleted.
-
-Version 1.2.9beta6 [March 6, 2006]
-  Fixed typo (RELEASE) in configuration files.
-
-Version 1.2.9beta7 [March 7, 2006]
-  Removed libpng.vers and libpng.sym from libpng12_la_SOURCES in Makefile.am
-  Fixed inconsistent #ifdef's around png_sig_bytes() and png_set_sCAL_s()
-    in png.h.
-  Updated makefile.elf as suggested by debian.
-  Made cosmetic changes to some makefiles, adding LN_SF and other macros.
-  Made some makefiles accept "exec_prefix".
-
-Version 1.2.9beta8 [March 9, 2006]
-  Fixed some "#if defined (..." which should be "#if defined(..."
-    Bug introduced in libpng-1.2.8.
-  Fixed inconsistency in definition of png_default_read_data()
-  Restored blank that was lost from makefile.sggcc "clean" target in beta7.
-  Revised calculation of "current" and "major" for irix in ltmain.sh
-  Changed "mkdir" to "MKDIR_P" in some makefiles.
-  Separated PNG_EXPAND and PNG_EXPAND_tRNS.
-  Added png_set_expand_gray_1_2_4_to_8() and deprecated
-    png_set_gray_1_2_4_to_8() which also expands tRNS to alpha.
-
-Version 1.2.9beta9 [March 10, 2006]
-  Include "config.h" in pngconf.h when available.
-  Added some checks for NULL png_ptr or NULL info_ptr (timeless)
-
-Version 1.2.9beta10 [March 20, 2006]
-  Removed extra CR from contrib/visualpng/VisualPng.dsw (Cosmin)
-  Made pnggccrd.c PIC-compliant (Christian Aichinger).
-  Added makefile.mingw (Wolfgang Glas).
-  Revised pngconf.h MMX checking.
-
-Version 1.2.9beta11 [March 22, 2006]
-  Fixed out-of-order declaration in pngwrite.c that was introduced in beta9
-  Simplified some makefiles by using LIBSO, LIBSOMAJ, and LIBSOVER macros.
-
-Version 1.2.9rc1 [March 31, 2006]
-  Defined PNG_USER_PRIVATEBUILD when including "pngusr.h" (Cosmin).
-  Removed nonsensical assertion check from pngtest.c (Cosmin).
-
-Version 1.2.9 [April 14, 2006]
-  Revised makefile.beos and added "none" selector in ltmain.sh
-
-Version 1.2.10beta1 [April 15, 2006]
-  Renamed "config.h" to "png_conf.h" and revised Makefile.am to add
-    -DPNG_BUILDING_LIBPNG to compile directive, and modified pngconf.h
-    to include png_conf.h only when PNG_BUILDING_LIBPNG is defined.
-
-Version 1.2.10beta2 [April 15, 2006]
-  Manually updated Makefile.in and configure.  Changed png_conf.h.in
-    back to config.h.
-
-Version 1.2.10beta3 [April 15, 2006]
-  Change png_conf.h back to config.h in pngconf.h.
-
-Version 1.2.10beta4 [April 16, 2006]
-  Change PNG_BUILDING_LIBPNG to PNG_CONFIGURE_LIBPNG in config/Makefile*.
-
-Version 1.2.10beta5 [April 16, 2006]
-  Added a configure check for compiling assembler code in pnggccrd.c
-
-Version 1.2.10beta6 [April 17, 2006]
-  Revised the configure check for pnggccrd.c
-  Moved -DPNG_CONFIGURE_LIBPNG into @LIBPNG_DEFINES@
-  Added @LIBPNG_DEFINES@ to arguments when building libpng.sym
-
-Version 1.2.10beta7 [April 18, 2006]
-  Change "exec_prefix=$prefix" to "exec_prefix=$(prefix)" in makefiles.
-
-Version 1.2.10rc1 [April 19, 2006]
-  Ensure pngconf.h doesn't define both PNG_USE_PNGGCCRD and PNG_USE_PNGVCRD
-  Fixed "LN_FS" typo in makefile.sco and makefile.solaris.
-
-Version 1.2.10rc2 [April 20, 2006]
-  Added a backslash between -DPNG_CONFIGURE_LIBPNG and -DPNG_NO_ASSEMBLER_CODE
-   in configure.ac and configure
-  Made the configure warning about versioned symbols less arrogant.
-
-Version 1.2.10rc3 [April 21, 2006]
-  Added a note in libpng.txt that png_set_sig_bytes(8) can be used when
-    writing an embedded PNG without the 8-byte signature.
-  Revised makefiles and configure to avoid making links to libpng.so.*
-
-Version 1.2.10 [April 23, 2006]
-  Reverted configure to "rc2" state.
-
-Version 1.2.11beta1 [May 31, 2006]
-  scripts/libpng.pc.in contained "configure" style version info and would
-    not work with makefiles.
-  The shared-library makefiles were linking to libpng.so.0 instead of
-    libpng.so.3 compatibility as the library.
-
-Version 1.2.11beta2 [June 2, 2006]
-  Increased sprintf buffer from 50 to 52 chars in pngrutil.c to avoid
-    buffer overflow.
-  Fixed bug in example.c (png_set_palette_rgb -> png_set_palette_to_rgb)
-
-Version 1.2.11beta3 [June 5, 2006]
-  Prepended "#! /bin/sh" to ltmail.sh and contrib/pngminus/*.sh (Cosmin).
-  Removed the accidental leftover Makefile.in~ (Cosmin).
-  Avoided potential buffer overflow and optimized buffer in
-    png_write_sCAL(), png_write_sCAL_s() (Cosmin).
-  Removed the include directories and libraries from CFLAGS and LDFLAGS
-    in scripts/makefile.gcc (Nelson A. de Oliveira, Cosmin).
-
-Version 1.2.11beta4 [June 6, 2006]
-  Allow zero-length IDAT chunks after the entire zlib datastream, but not
-    after another intervening chunk type.
-
-Version 1.0.19rc1, 1.2.11rc1 [June 13, 2006]
-  Deleted extraneous square brackets from [config.h] in configure.ac
-
-Version 1.0.19rc2, 1.2.11rc2 [June 14, 2006]
-  Added prototypes for PNG_INCH_CONVERSIONS functions to png.h
-  Revised INSTALL and autogen.sh
-  Fixed typo in several makefiles (-W1 should be -Wl)
-  Added typedef for png_int_32 and png_uint_32 on 64-bit systems.
-
-Version 1.0.19rc3, 1.2.11rc3 [June 15, 2006]
-  Removed the new typedefs for 64-bit systems (delay until version 1.4.0)
-  Added one zero element to png_gamma_shift[] array in pngrtran.c to avoid
-    reading out of bounds.
-
-Version 1.0.19rc4, 1.2.11rc4 [June 15, 2006]
-  Really removed the new typedefs for 64-bit systems.
-
-Version 1.0.19rc5, 1.2.11rc5 [June 22, 2006]
-  Removed png_sig_bytes entry from scripts/pngw32.def
-
-Version 1.0.19, 1.2.11 [June 26, 2006]
-  None.
-
-Version 1.0.20, 1.2.12 [June 27, 2006]
-  Really increased sprintf buffer from 50 to 52 chars in pngrutil.c to avoid
-    buffer overflow.
-
-Version 1.2.13beta1 [October 2, 2006]
-  Removed AC_FUNC_MALLOC from configure.ac
-  Work around Intel-Mac compiler bug by setting PNG_NO_MMX_CODE in pngconf.h
-  Change "logical" to "bitwise" throughout documentation.
-  Detect and fix attempt to write wrong iCCP profile length (CVE-2006-7244)
-
-Version 1.0.21, 1.2.13 [November 14, 2006]
-  Fix potential buffer overflow in sPLT chunk handler.
-  Fix Makefile.am to not try to link to noexistent files.
-  Check all exported functions for NULL png_ptr.
-
-Version 1.2.14beta1 [November 17, 2006]
-  Relocated three misplaced tests for NULL png_ptr.
-  Built Makefile.in with automake-1.9.6 instead of 1.9.2.
-  Build configure with autoconf-2.60 instead of 2.59
-
-Version 1.2.14beta2 [November 17, 2006]
-  Added some typecasts in png_zalloc().
-
-Version 1.2.14rc1 [November 20, 2006]
-  Changed "strtod" to "png_strtod" in pngrutil.c
-
-Version 1.0.22, 1.2.14    [November 27, 2006]
-  Added missing "$(srcdir)" in Makefile.am and Makefile.in
-
-Version 1.2.15beta1 [December 3, 2006]
-  Generated configure with autoconf-2.61 instead of 2.60
-  Revised configure.ac to update libpng.pc and libpng-config.
-
-Version 1.2.15beta2 [December 3, 2006]
-  Always export MMX asm functions, just stubs if not building pnggccrd.c
-
-Version 1.2.15beta3 [December 4, 2006]
-  Add "png_bytep" typecast to profile while calculating length in pngwutil.c
-
-Version 1.2.15beta4 [December 7, 2006]
-  Added scripts/CMakeLists.txt
-  Changed PNG_NO_ASSEMBLER_CODE to PNG_NO_MMX_CODE in scripts, like 1.4.0beta
-
-Version 1.2.15beta5 [December 7, 2006]
-  Changed some instances of PNG_ASSEMBLER_* to PNG_MMX_* in pnggccrd.c
-  Revised scripts/CMakeLists.txt
-
-Version 1.2.15beta6 [December 13, 2006]
-  Revised scripts/CMakeLists.txt and configure.ac
-
-Version 1.2.15rc1 [December 18, 2006]
-  Revised scripts/CMakeLists.txt
-
-Version 1.2.15rc2 [December 21, 2006]
-  Added conditional #undef jmpbuf in pngtest.c to undo #define in AIX headers.
-  Added scripts/makefile.nommx
-
-Version 1.2.15rc3 [December 25, 2006]
-  Fixed shared library numbering error that was introduced in 1.2.15beta6.
-
-Version 1.2.15rc4 [December 27, 2006]
-  Fixed handling of rgb_to_gray when png_ptr->color.gray isn't set.
-
-Version 1.2.15rc5 [December 31, 2006]
-  Revised handling of rgb_to_gray.
-
-Version 1.2.15 [January 5, 2007]
-  Added some (unsigned long) typecasts in pngtest.c to avoid printing errors.
-
-Version 1.2.16beta1 [January 6, 2007]
-  Fix bugs in makefile.nommx
-
-Version 1.2.16beta2 [January 16, 2007]
-  Revised scripts/CMakeLists.txt
-
-Version 1.2.16 [January 31, 2007]
-  No changes.
-
-Version 1.2.17beta1 [March 6, 2007]
-  Revised scripts/CMakeLists.txt to install both shared and static libraries.
-  Deleted a redundant line from pngset.c.
-
-Version 1.2.17beta2 [April 26, 2007]
-  Relocated misplaced test for png_ptr == NULL in pngpread.c
-  Change "==" to "&" for testing PNG_RGB_TO_GRAY_ERR & PNG_RGB_TO_GRAY_WARN
-    flags.
-  Changed remaining instances of PNG_ASSEMBLER_* to PNG_MMX_*
-  Added pngerror() when write_IHDR fails in deflateInit2().
-  Added "const" to some array declarations.
-  Mention examples of libpng usage in the libpng*.txt and libpng.3 documents.
-
-Version 1.2.17rc1 [May 4, 2007]
-  No changes.
-
-Version 1.2.17rc2 [May 8, 2007]
-  Moved several PNG_HAVE_* macros out of PNG_INTERNAL because applications
-    calling set_unknown_chunk_location() need them.
-  Changed transformation flag from PNG_EXPAND_tRNS to PNG_EXPAND in
-    png_set_expand_gray_1_2_4_to_8().
-  Added png_ptr->unknown_chunk to hold working unknown chunk data, so it
-    can be free'ed in case of error.  Revised unknown chunk handling in
-    pngrutil.c and pngpread.c to use this structure.
-
-Version 1.2.17rc3 [May 8, 2007]
-  Revised symbol-handling in configure script.
-
-Version 1.2.17rc4 [May 10, 2007]
-  Revised unknown chunk handling to avoid storing unknown critical chunks.
-
-Version 1.0.25 [May 15, 2007]
-Version 1.2.17 [May 15, 2007]
-  Added "png_ptr->num_trans=0" before error return in png_handle_tRNS,
-    to eliminate a vulnerability (CVE-2007-2445, CERT VU#684664)
-
-Version 1.0.26 [May 15, 2007]
-Version 1.2.18 [May 15, 2007]
-  Reverted the libpng-1.2.17rc3 change to symbol-handling in configure script
-
-Version 1.2.19beta1 [May 18, 2007]
-  Changed "const static" to "static PNG_CONST" everywhere, mostly undoing
-    change of libpng-1.2.17beta2.  Changed other "const" to "PNG_CONST"
-  Changed some handling of unused parameters, to avoid compiler warnings.
-    "if (unused == NULL) return;" becomes "unused = unused".
-
-Version 1.2.19beta2 [May 18, 2007]
-  Only use the valid bits of tRNS value in png_do_expand() (Brian Cartier)
-
-Version 1.2.19beta3 [May 19, 2007]
-  Add some "png_byte" typecasts in png_check_keyword() and write new_key
-  instead of key in zTXt chunk (Kevin Ryde).
-
-Version 1.2.19beta4 [May 21, 2007]
-  Add png_snprintf() function and use it in place of sprint() for improved
-    defense against buffer overflows.
-
-Version 1.2.19beta5 [May 21, 2007]
-  Fixed png_handle_tRNS() to only use the valid bits of tRNS value.
-  Changed handling of more unused parameters, to avoid compiler warnings.
-  Removed some PNG_CONST in pngwutil.c to avoid compiler warnings.
-
-Version 1.2.19beta6 [May 22, 2007]
-  Added some #ifdef PNG_MMX_CODE_SUPPORTED where needed in pngvcrd.c
-  Added a special "_MSC_VER" case that defines png_snprintf to _snprintf
-
-Version 1.2.19beta7 [May 22, 2007]
-  Squelched png_squelch_warnings() in pnggccrd.c and added
-    an #ifdef PNG_MMX_CODE_SUPPORTED block around the declarations that caused
-    the warnings that png_squelch_warnings was squelching.
-
-Version 1.2.19beta8 [May 22, 2007]
-  Removed __MMX__ from test in pngconf.h.
-
-Version 1.2.19beta9 [May 23, 2007]
-  Made png_squelch_warnings() available via PNG_SQUELCH_WARNINGS macro.
-  Revised png_squelch_warnings() so it might work.
-  Updated makefile.sgcc and makefile.solaris; added makefile.solaris-x86.
-
-Version 1.2.19beta10 [May 24, 2007]
-  Resquelched png_squelch_warnings(), use "__attribute__((used))" instead.
-
-Version 1.4.0beta1 [April 20, 2006]
-  Enabled iTXt support (changes png_struct, thus requires so-number change).
-  Cleaned up PNG_ASSEMBLER_CODE_SUPPORTED vs PNG_MMX_CODE_SUPPORTED
-  Eliminated PNG_1_0_X and PNG_1_2_X macros.
-  Removed deprecated functions png_read_init, png_write_init, png_info_init,
-    png_permit_empty_plte, png_set_gray_1_2_4_to_8, png_check_sig, and
-    removed the deprecated macro PNG_MAX_UINT.
-  Moved "PNG_INTERNAL" parts of png.h and pngconf.h into pngintrn.h
-  Removed many WIN32_WCE #ifdefs (Cosmin).
-  Reduced dependency on C-runtime library when on Windows (Simon-Pierre)
-  Replaced sprintf() with png_sprintf() (Simon-Pierre)
-
-Version 1.4.0beta2 [April 20, 2006]
-  Revised makefiles and configure to avoid making links to libpng.so.*
-  Moved some leftover MMX-related defines from pngconf.h to pngintrn.h
-  Updated scripts/pngos2.def, pngw32.def, and projects/wince/png32ce.def
-
-Version 1.4.0beta3 [May 10, 2006]
-  Updated scripts/pngw32.def to comment out MMX functions.
-  Added PNG_NO_GET_INT_32 and PNG_NO_SAVE_INT_32 macros.
-  Scripts/libpng.pc.in contained "configure" style version info and would
-    not work with makefiles.
-  Revised pngconf.h and added pngconf.h.in, so makefiles and configure can
-    pass defines to libpng and applications.
-
-Version 1.4.0beta4 [May 11, 2006]
-  Revised configure.ac, Makefile.am, and many of the makefiles to write
-    their defines in pngconf.h.
-
-Version 1.4.0beta5 [May 15, 2006]
-  Added a missing semicolon in Makefile.am and Makefile.in
-  Deleted extraneous square brackets from configure.ac
-
-Version 1.4.0beta6 [June 2, 2006]
-  Increased sprintf buffer from 50 to 52 chars in pngrutil.c to avoid
-    buffer overflow.
-  Changed sonum from 0 to 1.
-  Removed unused prototype for png_check_sig() from png.h
-
-Version 1.4.0beta7 [June 16, 2006]
-  Exported png_write_sig (Cosmin).
-  Optimized buffer in png_handle_cHRM() (Cosmin).
-  Set pHYs = 2835 x 2835 pixels per meter, and added
-    sCAL = 0.352778e-3 x 0.352778e-3 meters, in pngtest.png (Cosmin).
-  Added png_set_benign_errors(), png_benign_error(), png_chunk_benign_error().
-  Added typedef for png_int_32 and png_uint_32 on 64-bit systems.
-  Added "(unsigned long)" typecast on png_uint_32 variables in printf lists.
-
-Version 1.4.0beta8 [June 22, 2006]
-  Added demonstration of user chunk support in pngtest.c, to support the
-    public sTER chunk and a private vpAg chunk.
-
-Version 1.4.0beta9 [July 3, 2006]
-  Removed ordinals from scripts/pngw32.def and removed png_info_int and
-    png_set_gray_1_2_4_to_8 entries.
-  Inline call of png_get_uint_32() in png_get_uint_31().
-  Use png_get_uint_31() to get vpAg width and height in pngtest.c
-  Removed WINCE and Netware projects.
-  Removed standalone Y2KINFO file.
-
-Version 1.4.0beta10 [July 12, 2006]
-  Eliminated automatic copy of pngconf.h to pngconf.h.in from configure and
-    some makefiles, because it was not working reliably.  Instead, distribute
-    pngconf.h.in along with pngconf.h and cause configure and some of the
-    makefiles to update pngconf.h from pngconf.h.in.
-  Added pngconf.h to DEPENDENCIES in Makefile.am
-
-Version 1.4.0beta11 [August 19, 2006]
-  Removed AC_FUNC_MALLOC from configure.ac.
-  Added a warning when writing iCCP profile with mismatched profile length.
-  Patched pnggccrd.c to assemble on x86_64 platforms.
-  Moved chunk header reading into a separate function png_read_chunk_header()
-    in pngrutil.c.  The chunk header (len+sig) is now serialized in a single
-    operation (Cosmin).
-  Implemented support for I/O states. Added png_ptr member io_state, and
-    functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
-    (Cosmin).
-  Added png_get_io_chunk_name and png_get_io_state to scripts/*.def (Cosmin).
-  Renamed scripts/pngw32.* to scripts/pngwin.* (Cosmin).
-  Removed the include directories and libraries from CFLAGS and LDFLAGS
-    in scripts/makefile.gcc (Cosmin).
-  Used png_save_uint_32() to set vpAg width and height in pngtest.c (Cosmin).
-  Cast to proper type when getting/setting vpAg units in pngtest.c (Cosmin).
-  Added pngintrn.h to the Visual C++ projects (Cosmin).
-  Removed scripts/list (Cosmin).
-  Updated copyright year in scripts/pngwin.def (Cosmin).
-  Removed PNG_TYPECAST_NULL and used standard NULL consistently (Cosmin).
-  Disallowed the user to redefine png_size_t, and enforced a consistent use
-    of png_size_t across libpng (Cosmin).
-  Changed the type of png_ptr->rowbytes, PNG_ROWBYTES() and friends
-    to png_size_t (Cosmin).
-  Removed png_convert_size() and replaced png_sizeof with sizeof (Cosmin).
-  Removed some unnecessary type casts (Cosmin).
-  Changed prototype of png_get_compression_buffer_size() and
-    png_set_compression_buffer_size() to work with png_size_t instead of
-    png_uint_32 (Cosmin).
-  Removed png_memcpy_check() and png_memset_check() (Cosmin).
-  Fixed a typo (png_byte --> png_bytep) in libpng.3 and libpng.txt (Cosmin).
-  Clarified that png_zalloc() does not clear the allocated memory,
-    and png_zalloc() and png_zfree() cannot be PNGAPI (Cosmin).
-  Renamed png_mem_size_t to png_alloc_size_t, fixed its definition in
-    pngconf.h, and used it in all memory allocation functions (Cosmin).
-  Renamed pngintrn.h to pngpriv.h, added a comment at the top of the file
-    mentioning that the symbols declared in that file are private, and
-    updated the scripts and the Visual C++ projects accordingly (Cosmin).
-  Removed circular references between pngconf.h and pngconf.h.in in
-    scripts/makefile.vc*win32 (Cosmin).
-  Removing trailing '.' from the warning and error messages (Cosmin).
-  Added pngdefs.h that is built by makefile or configure, instead of
-    pngconf.h.in (Glenn).
-  Detect and fix attempt to write wrong iCCP profile length.
-
-Version 1.4.0beta12 [October 19, 2006]
-  Changed "logical" to "bitwise" in the documentation.
-  Work around Intel-Mac compiler bug by setting PNG_NO_MMX_CODE in pngconf.h
-  Add a typecast to stifle compiler warning in pngrutil.c
-
-Version 1.4.0beta13 [November 10, 2006]
-  Fix potential buffer overflow in sPLT chunk handler.
-  Fix Makefile.am to not try to link to noexistent files.
-
-Version 1.4.0beta14 [November 15, 2006]
-  Check all exported functions for NULL png_ptr.
-
-Version 1.4.0beta15 [November 17, 2006]
-  Relocated two misplaced tests for NULL png_ptr.
-  Built Makefile.in with automake-1.9.6 instead of 1.9.2.
-  Build configure with autoconf-2.60 instead of 2.59
-  Add "install: all" in Makefile.am so "configure; make install" will work.
-
-Version 1.4.0beta16 [November 17, 2006]
-  Added a typecast in png_zalloc().
-
-Version 1.4.0beta17 [December 4, 2006]
-  Changed "new_key[79] = '\0';" to "(*new_key)[79] = '\0';" in pngwutil.c
-  Add "png_bytep" typecast to profile while calculating length in pngwutil.c
-
-Version 1.4.0beta18 [December 7, 2006]
-  Added scripts/CMakeLists.txt
-
-Version 1.4.0beta19 [May 16, 2007]
-  Revised scripts/CMakeLists.txt
-  Rebuilt configure and Makefile.in with newer tools.
-  Added conditional #undef jmpbuf in pngtest.c to undo #define in AIX headers.
-  Added scripts/makefile.nommx
-
-Version 1.4.0beta20 [July 9, 2008]
-  Moved several PNG_HAVE_* macros from pngpriv.h to png.h because applications
-    calling set_unknown_chunk_location() need them.
-  Moved several macro definitions from pngpriv.h to pngconf.h
-  Merge with changes to the 1.2.X branch, as of 1.2.30beta04.
-  Deleted all use of the MMX assembler code and Intel-licensed optimizations.
-  Revised makefile.mingw
-
-Version 1.4.0beta21 [July 21, 2008]
-  Moved local array "chunkdata" from pngrutil.c to the png_struct, so
-    it will be freed by png_read_destroy() in case of a read error (Kurt
-    Christensen).
-
-Version 1.4.0beta22 [July 21, 2008]
-  Change "purpose" and "buffer" to png_ptr->chunkdata to avoid memory leaking.
-
-Version 1.4.0beta23 [July 22, 2008]
-  Change "chunkdata = NULL" to "png_ptr->chunkdata = NULL" several places in
-    png_decompress_chunk().
-
-Version 1.4.0beta24 [July 25, 2008]
-  Change all remaining "chunkdata" to "png_ptr->chunkdata" in
-    png_decompress_chunk(), and remove "chunkdata" from parameter list.
-  Put a call to png_check_chunk_name() in png_read_chunk_header().
-  Revised png_check_chunk_name() to reject a name with a lowercase 3rd byte.
-  Removed two calls to png_check_chunk_name() occurring later in the process.
-  Define PNG_NO_ERROR_NUMBERS by default in pngconf.h
-
-Version 1.4.0beta25 [July 30, 2008]
-  Added a call to png_check_chunk_name() in pngpread.c
-  Reverted png_check_chunk_name() to accept a name with a lowercase 3rd byte.
-  Added png_push_have_buffer() function to pngpread.c
-  Eliminated PNG_BIG_ENDIAN_SUPPORTED and associated png_get_* macros.
-  Made inline expansion of png_get_*() optional with PNG_USE_READ_MACROS.
-  Eliminated all PNG_USELESS_TESTS and PNG_CORRECT_PALETTE_SUPPORTED code.
-  Synced contrib directory and configure files with libpng-1.2.30beta06.
-  Eliminated no-longer-used pngdefs.h (but it's still built in the makefiles)
-  Relocated a misplaced "#endif /* PNG_NO_WRITE_FILTER */" in pngwutil.c
-
-Version 1.4.0beta26 [August 4, 2008]
-  Removed png_push_have_buffer() function in pngpread.c.  It increased the
-    compiled library size slightly.
-  Changed "-Wall" to "-W -Wall" in the CFLAGS in all makefiles (Cosmin Truta)
-  Declared png_ptr "volatile" in pngread.c and pngwrite.c to avoid warnings.
-  Updated contrib/visupng/cexcept.h to version 2.0.1
-  Added PNG_LITERAL_CHARACTER macros for #, [, and ].
-
-Version 1.4.0beta27 [August 5, 2008]
-  Revised usage of PNG_LITERAL_SHARP in pngerror.c.
-  Moved newline character from individual png_debug messages into the
-    png_debug macros.
-  Allow user to #define their own png_debug, png_debug1, and png_debug2.
-
-Version 1.4.0beta28 [August 5, 2008]
-  Revised usage of PNG_LITERAL_SHARP in pngerror.c.
-  Added PNG_STRING_NEWLINE macro
-
-Version 1.4.0beta29 [August 9, 2008]
-  Revised usage of PNG_STRING_NEWLINE to work on non-ISO compilers.
-  Added PNG_STRING_COPYRIGHT macro.
-  Added non-ISO versions of png_debug macros.
-
-Version 1.4.0beta30 [August 14, 2008]
-  Added premultiplied alpha feature (Volker Wiendl).
-
-Version 1.4.0beta31 [August 18, 2008]
-  Moved png_set_premultiply_alpha from pngtrans.c to pngrtran.c
-  Removed extra crc check at the end of png_handle_cHRM().  Bug introduced
-    in libpng-1.4.0beta20.
-
-Version 1.4.0beta32 [August 19, 2008]
-  Added PNG_WRITE_FLUSH_SUPPORTED block around new png_flush() call.
-  Revised PNG_NO_STDIO version of png_write_flush()
-
-Version 1.4.0beta33 [August 20, 2008]
-  Added png_get|set_chunk_cache_max() to limit the total number of sPLT,
-    text, and unknown chunks that can be stored.
-
-Version 1.4.0beta34 [September 6, 2008]
-  Shortened tIME_string to 29 bytes in pngtest.c
-  Fixed off-by-one error introduced in png_push_read_zTXt() function in
-    libpng-1.2.30beta04/pngpread.c (Harald van Dijk)
-
-Version 1.4.0beta35 [October 6, 2008]
-  Changed "trans_values" to "trans_color".
-  Changed so-number from 0 to 14.  Some OS do not like 0.
-  Revised makefile.darwin to fix shared library numbering.
-  Change png_set_gray_1_2_4_to_8() to png_set_expand_gray_1_2_4_to_8()
-    in example.c (debian bug report)
-
-Version 1.4.0beta36 [October 25, 2008]
-  Sync with tEXt vulnerability fix in libpng-1.2.33rc02.
-
-Version 1.4.0beta37 [November 13, 2008]
-  Added png_check_cHRM in png.c and moved checking from pngget.c, pngrutil.c,
-    and pngwrite.c
-
-Version 1.4.0beta38 [November 22, 2008]
-  Added check for zero-area RGB cHRM triangle in png_check_cHRM() and
-    png_check_cHRM_fixed().
-
-Version 1.4.0beta39 [November 23, 2008]
-  Revised png_warning() to write its message on standard output by default
-    when warning_fn is NULL.
-
-Version 1.4.0beta40 [November 24, 2008]
-  Eliminated png_check_cHRM().  Instead, always use png_check_cHRM_fixed().
-  In png_check_cHRM_fixed(), ensure white_y is > 0, and removed redundant
-    check for all-zero coordinates that is detected by the triangle check.
-
-Version 1.4.0beta41 [November 26, 2008]
-  Fixed string vs pointer-to-string error in png_check_keyword().
-  Rearranged test expressions in png_check_cHRM_fixed() to avoid internal
-    overflows.
-  Added PNG_NO_CHECK_cHRM conditional.
-
-Version 1.4.0beta42, 43 [December 1, 2008]
-  Merge png_debug with version 1.2.34beta04.
-
-Version 1.4.0beta44 [December 6, 2008]
-  Removed redundant check for key==NULL before calling png_check_keyword()
-    to ensure that new_key gets initialized and removed extra warning
-    (Merge with version 1.2.34beta05 -- Arvan Pritchard).
-
-Version 1.4.0beta45 [December 9, 2008]
-  In png_write_png(), respect the placement of the filler bytes in an earlier
-    call to png_set_filler() (Jim Barry).
-
-Version 1.4.0beta46 [December 10, 2008]
-  Undid previous change and added PNG_TRANSFORM_STRIP_FILLER_BEFORE and
-    PNG_TRANSFORM_STRIP_FILLER_AFTER conditionals and deprecated
-    PNG_TRANSFORM_STRIP_FILLER (Jim Barry).
-
-Version 1.4.0beta47 [December 15, 2008]
-  Support for dithering was disabled by default, because it has never
-    been well tested and doesn't work very well.  The code has not
-    been removed, however, and can be enabled by building libpng with
-    PNG_READ_DITHER_SUPPORTED defined.
-
-Version 1.4.0beta48 [February 14, 2009]
-  Added new exported function png_calloc().
-  Combined several instances of png_malloc(); png_memset() into png_calloc().
-  Removed prototype for png_freeptr() that was added in libpng-1.4.0beta24
-    but was never defined.
-
-Version 1.4.0beta49 [February 28, 2009]
-  Added png_fileno() macro to pngconf.h, used in pngwio.c
-  Corrected order of #ifdef's in png_debug definition in png.h
-  Fixed bug introduced in libpng-1.4.0beta48 with the memset arguments
-    for pcal_params.
-  Fixed order of #ifdef directives in the png_debug defines in png.h
-    (bug introduced in libpng-1.2.34/1.4.0beta29).
-  Revised comments in png_set_read_fn() and png_set_write_fn().
-
-Version 1.4.0beta50 [March 18, 2009]
-  Use png_calloc() instead of png_malloc() to allocate big_row_buf when
-    reading an interlaced file, to avoid a possible UMR.
-  Undid revision of PNG_NO_STDIO version of png_write_flush().  Users
-    having trouble with fflush() can build with PNG_NO_WRITE_FLUSH defined
-    or supply their own flush_fn() replacement.
-  Revised libpng*.txt and png.h documentation about use of png_write_flush()
-    and png_set_write_fn().
-  Removed fflush() from pngtest.c.
-  Added "#define PNG_NO_WRITE_FLUSH" to contrib/pngminim/encoder/pngusr.h
-
-Version 1.4.0beta51 [March 21, 2009]
-  Removed new png_fileno() macro from pngconf.h .
-
-Version 1.4.0beta52 [March 27, 2009]
-  Relocated png_do_chop() ahead of building gamma tables in pngrtran.c
-    This avoids building 16-bit gamma tables unnecessarily.
-  Removed fflush() from pngtest.c.
-  Added "#define PNG_NO_WRITE_FLUSH" to contrib/pngminim/encoder/pngusr.h
-  Added a section on differences between 1.0.x and 1.2.x to libpng.3/libpng.txt
-
-Version 1.4.0beta53 [April 1, 2009]
-  Removed some remaining MMX macros from pngpriv.h
-  Fixed potential memory leak of "new_name" in png_write_iCCP() (Ralph Giles)
-
-Version 1.4.0beta54 [April 13, 2009]
-  Added "ifndef PNG_SKIP_SETJMP_CHECK" block in pngconf.h to allow
-    application code writers to bypass the check for multiple inclusion
-    of setjmp.h when they know that it is safe to ignore the situation.
-  Eliminated internal use of setjmp() in pngread.c and pngwrite.c
-  Reordered ancillary chunks in pngtest.png to be the same as what
-    pngtest now produces, and made some cosmetic changes to pngtest output.
-  Eliminated deprecated png_read_init_3() and png_write_init_3() functions.
-
-Version 1.4.0beta55 [April 15, 2009]
-  Simplified error handling in pngread.c and pngwrite.c by putting
-    the new png_read_cleanup() and png_write_cleanup() functions inline.
-
-Version 1.4.0beta56 [April 25, 2009]
-  Renamed "user_chunk_data" to "my_user_chunk_data" in pngtest.c to suppress
-    "shadowed declaration" warning from gcc-4.3.3.
-  Renamed "gamma" to "png_gamma" in pngset.c to avoid "shadowed declaration"
-    warning about a global "gamma" variable in math.h on some platforms.
-
-Version 1.4.0beta57 [May 2, 2009]
-  Removed prototype for png_freeptr() that was added in libpng-1.4.0beta24
-    but was never defined (again).
-  Rebuilt configure scripts with autoconf-2.63 instead of 2.62
-  Removed pngprefs.h and MMX from makefiles
-
-Version 1.4.0beta58 [May 14, 2009]
-  Changed pngw32.def to pngwin.def in makefile.mingw (typo was introduced
-    in beta57).
-  Clarified usage of sig_bit versus sig_bit_p in example.c (Vincent Torri)
-
-Version 1.4.0beta59 [May 15, 2009]
-  Reformated sources in libpng style (3-space intentation, comment format)
-  Fixed typo in libpng docs (PNG_FILTER_AVE should be PNG_FILTER_AVG)
-  Added sections about the git repository and our coding style to the
-    documentation
-  Relocated misplaced #endif in pngwrite.c, sCAL chunk handler.
-
-Version 1.4.0beta60 [May 19, 2009]
-  Conditionally compile png_read_finish_row() which is not used by
-    progressive readers.
-  Added contrib/pngminim/preader to demonstrate building minimal progressive
-    decoder, based on contrib/gregbook with embedded libpng and zlib.
-
-Version 1.4.0beta61 [May 20, 2009]
-  In contrib/pngminim/*, renamed "makefile.std" to "makefile", since there
-    is only one makefile in those directories, and revised the README files
-    accordingly.
-  More reformatting of comments, mostly to capitalize sentences.
-
-Version 1.4.0beta62 [June 2, 2009]
-  Added "#define PNG_NO_WRITE_SWAP" to contrib/pngminim/encoder/pngusr.h
-    and "define PNG_NO_READ_SWAP" to decoder/pngusr.h and preader/pngusr.h
-  Reformatted several remaining "else statement" into two lines.
-  Added a section to the libpng documentation about using png_get_io_ptr()
-    in configure scripts to detect the presence of libpng.
-
-Version 1.4.0beta63 [June 15, 2009]
-  Revised libpng*.txt and libpng.3 to mention calling png_set_IHDR()
-    multiple times and to specify the sample order in the tRNS chunk,
-    because the ISO PNG specification has a typo in the tRNS table.
-  Changed several PNG_UNKNOWN_CHUNK_SUPPORTED to
-    PNG_HANDLE_AS_UNKNOWN_SUPPORTED, to make the png_set_keep mechanism
-    available for ignoring known chunks even when not saving unknown chunks.
-  Adopted preference for consistent use of "#ifdef" and "#ifndef" versus
-    "#if defined()" and "if !defined()" where possible.
-
-Version 1.4.0beta64 [June 24, 2009]
-  Eliminated PNG_LEGACY_SUPPORTED code.
-  Moved the various unknown chunk macro definitions outside of the
-    PNG_READ|WRITE_ANCILLARY_CHUNK_SUPPORTED blocks.
-
-Version 1.4.0beta65 [June 26, 2009]
-  Added a reference to the libpng license in each file.
-
-Version 1.4.0beta66 [June 27, 2009]
-  Refer to the libpng license instead of the libpng license in each file.
-
-Version 1.4.0beta67 [July 6, 2009]
-  Relocated INVERT_ALPHA within png_read_png() and png_write_png().
-  Added high-level API transform PNG_TRANSFORM_GRAY_TO_RGB.
-  Added an "xcode" project to the projects directory (Alam Arias).
-
-Version 1.4.0beta68 [July 19, 2009]
-  Avoid some tests in filter selection in pngwutil.c
-
-Version 1.4.0beta69 [July 25, 2009]
-  Simplified the new filter-selection test.  This runs faster in the
-    common "PNG_ALL_FILTERS" and PNG_FILTER_NONE cases.
-  Removed extraneous declaration from the new call to png_read_gray_to_rgb()
-    (bug introduced in libpng-1.4.0beta67).
-  Fixed up xcode project (Alam Arias)
-  Added a prototype for png_64bit_product() in png.c
-
-Version 1.4.0beta70 [July 27, 2009]
-  Avoid a possible NULL dereference in debug build, in png_set_text_2().
-    (bug introduced in libpng-0.95, discovered by Evan Rouault)
-
-Version 1.4.0beta71 [July 29, 2009]
-  Rebuilt configure scripts with autoconf-2.64.
-
-Version 1.4.0beta72 [August 1, 2009]
-  Replaced *.tar.lzma with *.tar.xz in distribution.  Get the xz codec
-    from <http://tukaani.org/xz>.
-
-Version 1.4.0beta73 [August 1, 2009]
-  Reject attempt to write iCCP chunk with negative embedded profile length
-    (JD Chen) (CVE-2009-5063).
-
-Version 1.4.0beta74 [August 8, 2009]
-  Changed png_ptr and info_ptr member "trans" to "trans_alpha".
-
-Version 1.4.0beta75 [August 21, 2009]
-  Removed an extra png_debug() recently added to png_write_find_filter().
-  Fixed incorrect #ifdef in pngset.c regarding unknown chunk support.
-
-Version 1.4.0beta76 [August 22, 2009]
-  Moved an incorrectly located test in png_read_row() in pngread.c
-
-Version 1.4.0beta77 [August 27, 2009]
-  Removed lpXYZ.tar.bz2 (with CRLF), KNOWNBUG, libpng-x.y.z-KNOWNBUG.txt,
-    and the "noconfig" files from the distribution.
-  Moved CMakeLists.txt from scripts into the main libpng directory.
-  Various bugfixes and improvements to CMakeLists.txt (Philip Lowman)
-
-Version 1.4.0beta78 [August 31, 2009]
-  Converted all PNG_NO_* tests to PNG_*_SUPPORTED everywhere except pngconf.h
-  Eliminated PNG_NO_FREE_ME and PNG_FREE_ME_SUPPORTED macros.
-  Use png_malloc plus a loop instead of png_calloc() to initialize
-    row_pointers in png_read_png().
-
-Version 1.4.0beta79 [September 1, 2009]
-  Eliminated PNG_GLOBAL_ARRAYS and PNG_LOCAL_ARRAYS; always use local arrays.
-  Eliminated PNG_CALLOC_SUPPORTED macro and always provide png_calloc().
-
-Version 1.4.0beta80 [September 17, 2009]
-  Removed scripts/libpng.icc
-  Changed typecast of filler from png_byte to png_uint_16 in png_set_filler().
-    (Dennis Gustafsson)
-  Fixed typo introduced in beta78 in pngtest.c ("#if def " should be "#ifdef ")
-
-Version 1.4.0beta81 [September 23, 2009]
-  Eliminated unused PNG_FLAG_FREE_* defines from pngpriv.h
-  Expanded TAB characters in pngrtran.c
-  Removed PNG_CONST from all "PNG_CONST PNG_CHNK" declarations to avoid
-    compiler complaints about doubly declaring things "const".
-  Changed all "#if [!]defined(X)" to "if[n]def X" where possible.
-  Eliminated unused png_ptr->row_buf_size
-
-Version 1.4.0beta82 [September 25, 2009]
-  Moved redundant IHDR checking into new png_check_IHDR() in png.c
-    and report all errors found in the IHDR data.
-  Eliminated useless call to png_check_cHRM() from pngset.c
-
-Version 1.4.0beta83 [September 25, 2009]
-  Revised png_check_IHDR() to eliminate bogus complaint about filter_type.
-
-Version 1.4.0beta84 [September 30, 2009]
-  Fixed some inconsistent indentation in pngconf.h
-  Revised png_check_IHDR() to add a test for width variable less than 32-bit.
-
-Version 1.4.0beta85 [October 1, 2009]
-  Revised png_check_IHDR() again, to check info_ptr members instead of
-    the contents of the returned parameters.
-
-Version 1.4.0beta86 [October 9, 2009]
-  Updated the "xcode" project (Alam Arias).
-  Eliminated a shadowed declaration of "pp" in png_handle_sPLT().
-
-Version 1.4.0rc01 [October 19, 2009]
-  Trivial cosmetic changes.
-
-Version 1.4.0beta87 [October 30, 2009]
-  Moved version 1.4.0 back into beta.
-
-Version 1.4.0beta88 [October 30, 2009]
-  Revised libpng*.txt section about differences between 1.2.x and 1.4.0
-    because most of the new features have now been ported back to 1.2.41
-
-Version 1.4.0beta89 [November 1, 2009]
-  More bugfixes and improvements to CMakeLists.txt (Philip Lowman)
-  Removed a harmless extra png_set_invert_alpha() from pngwrite.c
-  Apply png_user_chunk_cache_max within png_decompress_chunk().
-  Merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.
-
-Version 1.4.0beta90 [November 2, 2009]
-  Removed all remaining WIN32_WCE #ifdefs except those involving the
-    time.h "tm" structure
-
-Version 1.4.0beta91 [November 3, 2009]
-  Updated scripts/pngw32.def and projects/wince/png32ce.def
-  Copied projects/wince/png32ce.def to the scripts directory.
-  Added scripts/makefile.wce
-  Patched ltmain.sh for wince support.
-  Added PNG_CONVERT_tIME_SUPPORTED macro.
-
-Version 1.4.0beta92 [November 4, 2009]
-  Make inclusion of time.h in pngconf.h depend on PNG_CONVERT_tIME_SUPPORTED
-  Make #define PNG_CONVERT_tIME_SUPPORTED depend on PNG_WRITE_tIME_SUPPORTED
-  Revised libpng*.txt to describe differences from 1.2.40 to 1.4.0 (instead
-    of differences from 1.2.41 to 1.4.0)
-
-Version 1.4.0beta93 [November 7, 2009]
-  Added PNG_DEPSTRUCT, PNG_DEPRECATED, PNG_USE_RESULT, PNG_NORETURN, and
-    PNG_ALLOCATED macros to detect deprecated direct access to the
-    png_struct or info_struct members and other deprecated usage in
-    applications (John Bowler).
-  Updated scripts/makefile* to add "-DPNG_CONFIGURE_LIBPNG" to CFLAGS,
-    to prevent warnings about direct access to png structs by libpng
-    functions while building libpng.  They need to be tested, especially
-    those using compilers other than gcc.
-  Updated projects/visualc6 and visualc71 with "/d PNG_CONFIGURE_LIBPNG".
-    They should work but still need to be updated to remove
-    references to pnggccrd.c or pngvcrd.c and ASM building.
-  Added README.txt to the beos, cbuilder5, netware, and xcode projects warning
-    that they need to be updated, to remove references to pnggccrd.c and
-    pngvcrd.c and to depend on pngpriv.h
-  Removed three direct references to read_info_ptr members in pngtest.c
-    that were detected by the new PNG_DEPSTRUCT macro.
-  Moved the png_debug macro definitions and the png_read_destroy(),
-    png_write_destroy() and png_far_to_near() prototypes from png.h
-    to pngpriv.h (John Bowler)
-  Moved the synopsis lines for png_read_destroy(), png_write_destroy()
-    png_debug(), png_debug1(), and png_debug2() from libpng.3 to libpngpf.3.
-
-Version 1.4.0beta94 [November 9, 2009]
-  Removed the obsolete, unused pnggccrd.c and pngvcrd.c files.
-  Updated CMakeLists.txt to add "-DPNG_CONFIGURE_LIBPNG" to the definitions.
-  Removed dependency of pngtest.o on pngpriv.h in the makefiles.
-  Only #define PNG_DEPSTRUCT, etc. in pngconf.h if not already defined.
-
-Version 1.4.0beta95 [November 10, 2009]
-  Changed png_check_sig() to !png_sig_cmp() in contrib programs.
-  Added -DPNG_CONFIGURE_LIBPNG to contrib/pngminm/*/makefile
-  Changed png_check_sig() to !png_sig_cmp() in contrib programs.
-  Corrected the png_get_IHDR() call in contrib/gregbook/readpng2.c
-  Changed pngminim/*/gather.sh to stop trying to remove pnggccrd.c and pngvcrd.c
-  Added dependency on pngpriv.h in contrib/pngminim/*/makefile
-
-Version 1.4.0beta96 [November 12, 2009]
-  Renamed scripts/makefile.wce to scripts/makefile.cegcc
-  Revised Makefile.am to use libpng.sys while building libpng.so
-    so that only PNG_EXPORT functions are exported.
-  Removed the deprecated png_check_sig() function/macro.
-  Removed recently removed function names from scripts/*.def
-  Revised pngtest.png to put chunks in the same order written by pngtest
-    (evidently the same change made in libpng-1.0beta54 was lost).
-  Added PNG_PRIVATE macro definition in pngconf.h for possible future use.
-
-Version 1.4.0beta97 [November 13, 2009]
-  Restored pngtest.png to the libpng-1.4.0beta7 version.
-  Removed projects/beos and netware.txt; no one seems to be supporting them.
-  Revised Makefile.in
-
-Version 1.4.0beta98 [November 13, 2009]
-  Added the "xcode" project to zip distributions,
-  Fixed a typo in scripts/pngwin.def introduced in beta97.
-
-Version 1.4.0beta99 [November 14, 2009]
-  Moved libpng-config.in and libpng.pc-configure.in out of the scripts
-    directory, to libpng-config.in and libpng-pc.in, respectively, and
-    modified Makefile.am and configure.ac accordingly.  Now "configure"
-    needs nothing from the "scripts" directory.
-  Avoid redefining PNG_CONST in pngconf.h
-
-Version 1.4.0beta100 [November 14, 2009]
-  Removed ASM builds from projects/visualc6 and projects/visualc71
-  Removed scripts/makefile.nommx and makefile.vcawin32
-  Revised CMakeLists.txt to account for new location of libpng-config.in
-    and libpng-pc.in
-  Updated INSTALL to reflect removal and relocation of files.
-
-Version 1.4.0beta101 [November 14, 2009]
-  Restored the binary files (*.jpg, *.png, some project files) that were
-    accidentally deleted from the zip and 7z distributions when the xcode
-    project was added.
-
-Version 1.4.0beta102 [November 18, 2009]
-  Added libpng-config.in and libpng-pc.in to the zip and 7z distributions.
-  Fixed a typo in projects/visualc6/pngtest.dsp, introduced in beta100.
-  Moved descriptions of makefiles and other scripts out of INSTALL into
-    scripts/README.txt
-  Updated the copyright year in scripts/pngwin.rc from 2006 to 2009.
-
-Version 1.4.0beta103 [November 21, 2009]
-  Removed obsolete comments about ASM from projects/visualc71/README_zlib.txt
-  Align row_buf on 16-byte boundary in memory.
-  Restored the PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED guard around the call
-    to png_flush() after png_write_IEND().  See 1.4.0beta32, 1.4.0beta50
-    changes above and 1.2.30, 1.2.30rc01 and rc03 in 1.2.41 CHANGES.  Someone
-    needs this feature.
-  Make the 'png_jmpbuf' macro expand to a call that records the correct
-    longjmp function as well as returning a pointer to the setjmp
-    jmp_buf buffer, and marked direct access to jmpbuf 'deprecated'.
-    (John Bowler)
-
-Version 1.4.0beta104 [November 22, 2009]
-  Removed png_longjmp_ptr from scripts/*.def and libpng.3
-  Rebuilt configure scripts with autoconf-2.65
-
-Version 1.4.0beta105 [November 25, 2009]
-  Use fast integer PNG_DIVIDE_BY_255() or PNG_DIVIDE_BY_65535()
-    to accomplish alpha premultiplication when
-    PNG_READ_COMPOSITE_NODIV_SUPPORTED is defined.
-  Changed "/255" to "/255.0" in background calculations to make it clear
-    that the 255 is used as a double.
-
-Version 1.4.0beta106 [November 27, 2009]
-  Removed premultiplied alpha feature.
-
-Version 1.4.0beta107 [December 4, 2009]
-  Updated README
-  Added "#define PNG_NO_PEDANTIC_WARNINGS" in the libpng source files.
-  Removed "-DPNG_CONFIGURE_LIBPNG" from the makefiles and projects.
-  Revised scripts/makefile.netbsd, makefile.openbsd, and makefile.sco
-    to put png.h and pngconf.h in $prefix/include, like the other scripts,
-    instead of in $prefix/include/libpng.  Also revised makefile.sco
-    to put them in $prefix/include/libpng15 instead of in
-    $prefix/include/libpng/libpng15.
-
-Version 1.4.0beta108 [December 11, 2009]
-  Removed leftover "-DPNG_CONFIGURE_LIBPNG" from contrib/pngminim/*/makefile
-  Relocated png_do_chop() to its original position in pngrtran.c; the
-    change in version 1.2.41beta08 caused transparency to be handled wrong
-    in some 16-bit datastreams (Yusaku Sugai).
-
-Version 1.4.0beta109 [December 13, 2009]
-  Added "bit_depth" parameter to the private png_build_gamma_table() function.
-  Pass bit_depth=8 to png_build_gamma_table() when bit_depth is 16 but the
-    PNG_16_TO_8 transform has been set, to avoid unnecessary build of 16-bit
-    tables.
-
-Version 1.4.0rc02 [December 20, 2009]
-  Declared png_cleanup_needed "volatile" in pngread.c and pngwrite.c
-
-Version 1.4.0rc03 [December 22, 2009]
-  Renamed libpng-pc.in back to libpng.pc.in and revised CMakeLists.txt
-    (revising the change in 1.4.0beta99)
-
-Version 1.4.0rc04 [December 25, 2009]
-  Swapped PNG_UNKNOWN_CHUNKS_SUPPORTED and PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-    in pngset.c to be consistent with other changes in version 1.2.38.
-
-Version 1.4.0rc05 [December 25, 2009]
-  Changed "libpng-pc.in" to "libpng.pc.in" in configure.ac, configure, and
-    Makefile.in to be consistent with changes in libpng-1.4.0rc03
-
-Version 1.4.0rc06 [December 29, 2009]
-  Reverted the gamma_table changes from libpng-1.4.0beta109.
-  Fixed some indentation errors.
-
-Version 1.4.0rc07 [January 1, 2010]
-  Revised libpng*.txt and libpng.3 about 1.2.x->1.4.x differences.
-  Use png_calloc() instead of png_malloc(); png_memset() in pngrutil.c
-  Update copyright year to 2010.
-
-Version 1.4.0rc08 [January 2, 2010]
-  Avoid deprecated references to png_ptr-io_ptr and png_ptr->error_ptr
-    in pngtest.c
-
-Version 1.4.0 [January 3, 2010]
-  No changes.
-
-Version 1.4.1beta01 [January 8, 2010]
-  Updated CMakeLists.txt for consistent indentation and to avoid an
-    unclosed if-statement warning (Philip Lowman).
-  Revised Makefile.am and Makefile.in to remove references to Y2KINFO,
-    KNOWNBUG, and libpng.la (Robert Schwebel).
-  Revised the makefiles to install the same files and symbolic
-    links as configure, except for libpng.la and libpng14.la.
-  Make png_set|get_compression_buffer_size() available even when
-    PNG_WRITE_SUPPORTED is not enabled.
-  Revised Makefile.am and Makefile.in to simplify their maintenance.
-  Revised scripts/makefile.linux to install a link to libpng14.so.14.1
-
-Version 1.4.1beta02 [January 9, 2010]
-  Revised the rest of the makefiles to install a link to libpng14.so.14.1
-
-Version 1.4.1beta03 [January 10, 2010]
-  Removed png_set_premultiply_alpha() from scripts/*.def
-
-Version 1.4.1rc01 [January 16, 2010]
-  No changes.
-
-Version 1.4.1beta04 [January 23, 2010]
-  Revised png_decompress_chunk() to improve speed and memory usage when
-    decoding large chunks.
-  Added png_set|get_chunk_malloc_max() functions.
-
-Version 1.4.1beta05 [January 26, 2010]
-  Relocated "int k" declaration in pngtest.c to minimize its scope.
-
-Version 1.4.1beta06 [January 28, 2010]
-  Revised png_decompress_chunk() to use a two-pass method suggested by
-    John Bowler.
-
-Version 1.4.1beta07 [February 6, 2010]
-  Folded some long lines in the source files.
-  Added defineable PNG_USER_CHUNK_CACHE_MAX, PNG_USER_CHUNK_MALLOC_MAX,
-    and a PNG_USER_LIMITS_SUPPORTED flag.
-  Eliminated use of png_ptr->irowbytes and reused the slot in png_ptr as
-    png_ptr->png_user_chunk_malloc_max.
-  Revised png_push_save_buffer() to do fewer but larger png_malloc() calls.
-
-Version 1.4.1beta08 [February 6, 2010]
-  Minor cleanup and updating of dates and copyright year.
-
-Version 1.5.0beta01 [February 7, 2010]
-  Moved declaration of png_struct into private pngstruct.h and png_info
-    into pnginfo.h
-
-Version 1.4.1beta09 and 1.5.0beta02 [February 7, 2010]
-  Reverted to original png_push_save_buffer() code.
-
-Version 1.4.1beta10 and 1.5.0beta03 [February 8, 2010]
-  Return allocated "old_buffer" in png_push_save_buffer() before
-    calling png_error(), to avoid a potential memory leak.
-  Updated configure script to use SO number 15.
-
-Version 1.5.0beta04 [February 9, 2010]
-  Removed malformed "incomplete struct declaration" of png_info from png.h
-
-Version 1.5.0beta05 [February 12, 2010]
-  Removed PNG_DEPSTRUCT markup in pngstruct.h and pnginfo.h, and undid the
-    linewrapping that it entailed.
-  Revised comments in pngstruct.h and pnginfo.h and added pointers to
-    the libpng license.
-  Changed PNG_INTERNAL to PNG_EXPOSE_INTERNAL_STRUCTURES
-  Removed the cbuilder5 project, which has not been updated to 1.4.0.
-
-Version 1.4.1beta12 and 1.5.0beta06 [February 14, 2010]
-  Fixed type declaration of png_get_chunk_malloc_max() in pngget.c (Daisuke
-    Nishikawa)
-
-Version 1.5.0beta07 [omitted]
-
-Version 1.5.0beta08 [February 19, 2010]
-  Changed #ifdef PNG_NO_STDIO_SUPPORTED to #ifdef PNG_NO_CONSOLE_IO_SUPPORTED
-    wherever png_snprintf() is used to construct error and warning messages.
-  Noted in scripts/makefile.mingw that it expects to be run under MSYS.
-  Removed obsolete unused MMX-querying support from contrib/gregbook
-  Added exported png_longjmp() function.
-  Removed the AIX redefinition of jmpbuf in png.h
-  Added -D_ALLSOURCE in configure.ac, makefile.aix, and CMakeLists.txt
-    when building on AIX.
-
-Version 1.5.0beta09 [February 19, 2010]
-  Removed -D_ALLSOURCE from configure.ac, makefile.aix, and CMakeLists.txt.
-  Changed the name of png_ptr->jmpbuf to png_ptr->png_jmpbuf in pngstruct.h
-
-Version 1.5.0beta10 [February 25, 2010]
-  Removed unused gzio.c from contrib/pngminim gather and makefile scripts
-  Removed replacement error handlers from contrib/gregbook.  Because of
-    the new png_longjmp() function they are no longer needed.
-
-Version 1.5.0beta11 [March 6, 2010]
-  Removed checking for already-included setjmp.h from pngconf.h
-  Fixed inconsistent indentations and made numerous cosmetic changes.
-  Revised the "SEE ALSO" style of libpng.3, libpngpf.3, and png.5
-
-Version 1.5.0beta12 [March 9, 2010]
-  Moved "#include png.h" inside pngpriv.h and removed "#include png.h" from
-    the source files, along with "#define PNG_EXPOSE_INTERNAL_STRUCTURES"
-    and "#define PNG_NO_PEDANTIC_WARNINGS" (John Bowler).
-  Created new pngdebug.h and moved debug definitions there.
-
-Version 1.5.0beta13 [March 10, 2010]
-  Protect pngstruct.h, pnginfo.h, and pngdebug.h from being included twice.
-  Revise the "#ifdef" blocks in png_inflate() so it will compile when neither
-    PNG_USER_CHUNK_MALLOC_MAX nor PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
-    is defined.
-  Removed unused png_measure_compressed_chunk() from pngpriv.h and libpngpf.3
-  Moved the 'config.h' support from pngconf.h to pngpriv.h
-  Removed PNGAPI from the png_longjmp_ptr typedef.
-  Eliminated dependence of pngtest.c on the private pngdebug.h file.
-  Make all png_debug macros into *unterminated* statements or
-    expressions (i.e. a trailing ';' must always be added) and correct
-    the format statements in various png_debug messages.
-
-Version 1.5.0beta14 [March 14, 2010]
-  Removed direct access to png_ptr->io_ptr from the Windows code in pngtest.c
-  Revised Makefile.am to account for recent additions and replacements.
-  Corrected CE and OS/2 DEF files (scripts/png*def) for symbols removed and
-    added ordinal numbers to the Windows DEF file and corrected the duplicated
-    ordinal numbers on CE symbols that are commented out.
-  Added back in export symbols that can be present in the Windows build but
-    are disabled by default.
-  PNG_EXPORT changed to include an 'ordinal' field for DEF file generation.
-    PNG_CALLBACK added to make callback definitions uniform.  PNGAPI split
-    into PNGCAPI (base C form), PNGAPI (exports) and PNGCBAPI (callbacks),
-    and appropriate changes made to all files.  Cygwin builds re-hinged to
-    allow procedure call standard changes and to remove the need for the DEF
-    file (fixes build on Cygwin).
-  Enabled 'attribute' warnings that are relevant to library APIs and callbacks.
-  Changed rules for generation of the various symbol files and added a new
-    rule for a DEF file (which is also added to the distribution).
-  Updated the symbol file generation to stop it adding spurious spaces
-    to EOL (coming from preprocessor macro expansion).  Added a facility
-    to join tokens in the output and rewrite *.dfn to use this.
-  Eliminated scripts/*.def in favor of libpng.def; updated projects/visualc71
-    and removed scripts/makefile.cygwin.
-  Made PNG_BUILD_DLL safe: it can be set whenever a DLL is being built.
-  Removed the include of sys/types.h - apparently unnecessary now on the
-    platforms on which it happened (all but Mac OS and RISC OS).
-  Moved the Mac OS test into pngpriv.h (the only place it is used.)
-
-Version 1.5.0beta15 [March 17, 2010]
-  Added symbols.chk target to Makefile.am to validate the symbols in png.h
-    against the new DEF file scripts/symbols.def.
-  Changed the default DEF file back to pngwin.def.
-  Removed makefile.mingw.
-  Eliminated PNG_NO_EXTERN and PNG_ALL_EXTERN
-
-Version 1.5.0beta16 [April 1, 2010]
-  Make png_text_struct independent of PNG_iTXt_SUPPORTED, so that
-    fields are initialized in all configurations.  The READ/WRITE
-    macros (PNG_(READ|WRITE)_iTXt_SUPPORTED) still function as
-    before to disable code to actually read or write iTXt chunks
-    and iTXt_SUPPORTED can be used to detect presence of either
-    read or write support (but it is probably better to check for
-    the one actually required - read or write.)
-  Combined multiple png_warning() calls for a single error.
-  Restored the macro definition of png_check_sig().
-
-Version 1.5.0beta17 [April 17, 2010]
-  Added some "(long)" typecasts to printf calls in png_handle_cHRM().
-  Documented the fact that png_set_dither() was disabled since libpng-1.4.0.
-  Reenabled png_set_dither() but renamed it to png_set_quantize() to reflect
-    more accurately what it actually does.  At the same time, renamed
-    the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros to
-    PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
-  Added some "(long)" typecasts to printf calls in png_handle_cHRM().
-  Freeze build-time only configuration in the build.
-    In all prior versions of libpng most configuration options
-    controlled by compiler #defines had to be repeated by the
-    application code that used libpng.  This patch changes this
-    so that compilation options that can only be changed at build
-    time are frozen in the build.  Options that are compiler
-    dependent (and those that are system dependent) are evaluated
-    each time - pngconf.h holds these.  Options that can be changed
-    per-file in the application are in png.h.  Frozen options are
-    in the new installed header file pnglibconf.h (John Bowler)
-  Removed the xcode project because it has not been updated to work
-    with libpng-1.5.0.
-  Removed the ability to include optional pngusr.h
-
-Version 1.5.0beta18 [April 17, 2010]
-  Restored the ability to include optional pngusr.h
-  Moved replacements for png_error() and png_warning() from the
-    contrib/pngminim project to pngerror.c, for use when warnings or
-    errors are disabled via PNG_NO_WARN or PNG_NO_ERROR_TEXT, to avoid
-    storing unneeded error/warning text.
-  Updated contrib/pngminim project to work with the new pnglibconf.h
-  Added some PNG_NO_* defines to contrib/pngminim/*/pngusr.h to save space.
-
-Version 1.5.0beta19 [April 24, 2010]
-  Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED.  This allows the functions
-    to read and write ints to be disabled independently of PNG_USE_READ_MACROS,
-    which allows libpng to be built with the functions even though the default
-    is to use the macros - this allows applications to choose at app build
-    time whether or not to use macros (previously impossible because the
-    functions weren't in the default build.)
-  Changed Windows calling convention back to __cdecl for API functions.
-    For Windows/x86 platforms only:
-      __stdcall is no longer needed for Visual Basic, so libpng-1.5.0 uses
-      __cdecl throughout (both API functions and callbacks) on Windows/x86
-      platforms.
-  Replaced visualc6 and visualc71 projects with new vstudio project
-  Relaxed the overly-restrictive permissions of some files.
-
-Version 1.5.0beta20 [April 24, 2010]
-  Relaxed more overly-restrictive permissions of some files.
-
-Version 1.5.0beta21 [April 27, 2010]
-  Removed some unwanted binary bytes and changed CRLF to NEWLINE in the new
-    vstudio project files, and some trivial editing of some files in the
-    scripts directory.
-  Set PNG_NO_READ_BGR, PNG_NO_IO_STATE, and PNG_NO_TIME_RFC1123 in
-    contrib/pngminim/decoder/pngusr.h to make a smaller decoder application.
-
-Version 1.5.0beta22 [April 28, 2010]
-  Fixed dependencies of GET_INT_32 - it does not require READ_INT_FUNCTIONS
-    because it has a macro equivalent.
-  Improved the options.awk script; added an "everything off" option.
-  Revised contrib/pngminim to use the "everything off" option in pngusr.dfa.
-
-Version 1.5.0beta23 [April 29, 2010]
-  Corrected PNG_REMOVED macro to take five arguments.
-    The macro was documented with two arguments (name,ordinal), however
-    the symbol checking .dfn files assumed five arguments.  The five
-    argument form seems more useful so it is changed to that.
-  Corrected PNG_UNKNOWN_CHUNKS_SUPPORTED to PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-    in gregbook/readpng2.c
-  Corrected protection of png_get_user_transform_ptr. The API declaration in
-    png.h is removed if both READ and WRITE USER_TRANSFORM are turned off
-    but was left defined in pngtrans.c
-  Added logunsupported=1 to cause pnglibconf.h to document disabled options.
-    This makes the installed pnglibconf.h more readable but causes no
-    other change.  The intention is that users of libpng will find it
-    easier to understand if an API they need is missing.
-  Include png_reset_zstream() in png.c only when PNG_READ_SUPPORTED is defined.
-  Removed dummy_inflate.c from contrib/pngminim/encoder
-  Removed contrib/pngminim/*/gather.sh; gathering is now done in the makefile.
-
-Version 1.5.0beta24 [May 7, 2010]
-  Use bitwise "&" instead of arithmetic mod in pngrutil.c calculation of the
-    offset of the png_ptr->rowbuf pointer into png_ptr->big_row_buf.
-  Added more blank lines for readability.
-
-Version 1.5.0beta25 [June 18, 2010]
-  In pngpread.c: png_push_have_row() add check for new_row > height
-  Removed the now-redundant check for out-of-bounds new_row from example.c
-
-Version 1.5.0beta26 [June 18, 2010]
-  In pngpread.c: png_push_process_row() add check for too many rows.
-
-Version 1.5.0beta27 [June 18, 2010]
-  Removed the check added in beta25 as it is now redundant.
-
-Version 1.5.0beta28 [June 20, 2010]
-  Rewrote png_process_IDAT_data to consistently treat extra data as warnings
-    and handle end conditions more cleanly.
-  Removed the new (beta26) check in png_push_process_row().
-
-Version 1.5.0beta29 [June 21, 2010]
-  Revised scripts/options.awk to work on Sunos (but still doesn't work)
-  Added comment to options.awk and contrib/pngminim/*/makefile to try nawk.
-
-Version 1.5.0beta30 [June 22, 2010]
-  Stop memory leak when reading a malformed sCAL chunk.
-
-Version 1.5.0beta31 [June 26, 2010]
-  Revised pngpread.c patch of beta28 to avoid an endless loop.
-  Removed some trailing blanks.
-
-Version 1.5.0beta32 [June 26, 2010]
-  Removed leftover scripts/options.patch and scripts/options.rej
-
-Version 1.5.0beta33 [July 6, 3010]
-  Made FIXED and FLOATING options consistent in the APIs they enable and
-    disable.  Corrected scripts/options.awk to handle both command line
-    options and options specified in the .dfa files.
-  Changed char *msg to PNG_CONST char *msg in pngrutil.c
-  Make png_set_sRGB_gAMA_and_cHRM set values using either the fixed or
-    floating point APIs, but not both.
-  Reversed patch to remove error handler when the jmp_buf is stored in the
-    main program structure, not the png_struct.
-    The error handler is needed because the default handler in libpng will
-    always use the jmp_buf in the library control structure; this is never
-    set.  The gregbook code is a useful example because, even though it
-    uses setjmp/longjmp, it shows how error handling can be implemented
-    using control mechanisms not directly supported by libpng.  The
-    technique will work correctly with mechanisms such as Microsoft
-    Structure Exceptions or C++ exceptions (compiler willing - note that gcc
-    does not by default support interworking of C and C++ error handling.)
-  Reverted changes to call png_longjmp in contrib/gregbook where it is not
-    appropriate.  If mainprog->jmpbuf is used by setjmp, then png_longjmp
-    cannot be used.
-  Changed "extern PNG_EXPORT" to "PNG_EXPORT" in png.h (Jan Nijtmans)
-  Changed "extern" to "PNG_EXTERN" in pngpriv.h (except for the 'extern "C" {')
-
-Version 1.5.0beta34 [July 12, 2010]
-  Put #ifndef PNG_EXTERN, #endif around the define PNG_EXTERN in pngpriv.h
-
-Version 1.5.0beta35 [July 24, 2010]
-  Removed some newly-added TAB characters.
-  Added -DNO_PNG_SNPRINTF to CFLAGS in scripts/makefile.dj2
-  Moved the definition of png_snprintf() outside of the enclosing
-    #ifdef blocks in pngconf.h
-
-Version 1.5.0beta36 [July 29, 2010]
-  Patches by John Bowler:
-  Fixed point APIs are now supported throughout (no missing APIs).
-  Internal fixed point arithmetic support exists for all internal floating
-    point operations.
-  sCAL validates the floating point strings it is passed.
-  Safe, albeit rudimentary, Watcom support is provided by PNG_API_RULE==2
-  Two new APIs exist to get the number of passes without turning on the
-    PNG_INTERLACE transform and to get the number of rows in the current
-    pass.
-  A new test program, pngvalid.c, validates the gamma code.
-  Errors in the 16-bit gamma correction (overflows) have been corrected.
-  cHRM chunk testing is done consistently (previously the floating point
-    API bypassed it, because the test really didn't work on FP, now the test
-    is performed on the actual values to be stored in the PNG file so it
-    works in the FP case too.)
-  Most floating point APIs now simply call the fixed point APIs after
-    converting the values to the fixed point form used in the PNG file.
-  The standard headers no longer include zlib.h, which is currently only
-    required for pngstruct.h and can therefore be internal.
-  Revised png_get_int_32 to undo the PNG two's complement representation of
-    negative numbers.
-
-Version 1.5.0beta37 [July 30, 2010]
-  Added a typecast in png_get_int_32() in png.h and pngrutil.h to avoid
-    a compiler warning.
-  Replaced oFFs 0,0 with oFFs -10,20 in pngtest.png
-
-Version 1.5.0beta38 [July 31, 2010]
-  Implemented remaining "_fixed" functions.
-  Corrected a number of recently introduced warnings mostly resulting from
-    safe but uncast assignments to shorter integers.  Also added a zlib
-    VStudio release library project because the latest zlib Official Windows
-    build does not include such a thing.
-  Revised png_get_int_16() to be similar to png_get_int_32().
-  Restored projects/visualc71.
-
-Version 1.5.0beta39 [August 2, 2010]
-  VisualC/GCC warning fixes, VisualC build fixes
-  The changes include support for function attributes in VC in addition to
-    those already present in GCC - necessary because without these some
-    warnings are unavoidable.  Fixes include signed/unsigned fixes in
-    pngvalid and checks with gcc -Wall -Wextra -Wunused.
-  VC requires function attributes on function definitions as well as
-    declarations, PNG_FUNCTION has been added to enable this and the
-    relevant function definitions changed.
-
-Version 1.5.0beta40 [August 6, 2010]
-  Correct use of _WINDOWS_ in pngconf.h
-  Removed png_mem_ #defines; they are no longer used.
-  Added the sRGB chunk to pngtest.png
-
-Version 1.5.0beta41 [August 11, 2010]
-  Added the cHRM chunk to pngtest.png
-  Don't try to use version-script with cygwin/mingw.
-  Revised contrib/gregbook to work under cygwin/mingw.
-
-Version 1.5.0beta42 [August 18, 2010]
-  Add .dll.a to the list of extensions to be symlinked by Makefile.am (Yaakov)
-  Made all API functions that have const arguments and constant string
-    literal pointers declare them (John Bowler).
-
-Version 1.5.0beta43 [August 20, 2010]
-  Removed spurious tabs, shorten long lines (no source change)
-    Also added scripts/chkfmt to validate the format of all the files that can
-    reasonably be validated (it is suggested to run "make distclean" before
-    checking, because some machine generated files have long lines.)
-  Reformatted the CHANGES file to be more consistent throughout.
-  Made changes to address various issues identified by GCC, mostly
-    signed/unsigned and shortening problems on assignment but also a few
-    difficult to optimize (for GCC) loops.
-  Fixed non-GCC fixed point builds.  In png.c a declaration was misplaced
-    in an earlier update.  Fixed to declare the auto variables at the head.
-  Use cexcept.h in pngvalid.c.
-
-Version 1.5.0beta44 [August 24, 2010]
-  Updated CMakeLists.txt to use CMAKE_INSTALL_LIBDIR variable; useful for
-    installing libpng in /usr/lib64 (Funda Wang).
-  Revised CMakeLists.txt to put the man pages in share/man/man* not man/man*
-  Revised CMakeLists.txt to make symlinks instead of copies when installing.
-  Changed PNG_LIB_NAME from pngNN to libpngNN in CMakeLists.txt (Philip Lowman)
-  Implemented memory checks within pngvalid
-  Reformatted/rearranged pngvalid.c to assist use of progressive reader.
-  Check interlaced images in pngvalid
-  Clarified pngusr.h comments in pnglibconf.dfa
-  Simplified the pngvalid error-handling code now that cexcept.h is in place.
-  Implemented progressive reader in pngvalid.c for standard tests
-  Implemented progressive read in pngvalid.c gamma tests
-  Turn on progressive reader in pngvalid.c by default and tidy code.
-
-Version 1.5.0beta45 [August 26, 2010]
-  Added an explicit make step to projects/vstudio for pnglibconf.h
-    Also corrected zlib.vcxproj into which Visual Studio had introduced
-    what it calls an "authoring error".  The change to make pnglibconf.h
-    simply copies the file; in the future it may actually generate the
-    file from scripts/pnglibconf.dfa as the other build systems do.
-  Changed pngvalid to work when floating point APIs are disabled
-  Renamed the prebuilt scripts/pnglibconf.h to scripts/pnglibconf.h.prebuilt
-  Supply default values for PNG_USER_PRIVATEBUILD and PNG_USER_DLLFNAME_POSTFIX
-    in pngpriv.h in case the user neglected to define them in their pngusr.h
-
-Version 1.5.0beta46 [August 28, 2010]
-  Added new private header files to libpng_sources in CMakeLists.txt
-  Added PNG_READ_16BIT, PNG_WRITE_16BIT, and PNG_16BIT options.
-  Added reference to scripts/pnglibconf.h.prebuilt in the visualc71 project.
-
-Version 1.5.0beta47 [September 11, 2010]
-  Fixed a number of problems with 64-bit compilation reported by Visual
-    Studio 2010 (John Bowler).
-
-Version 1.5.0beta48 [October 4, 2010]
-  Updated CMakeLists.txt (Philip Lowman).
-  Revised autogen.sh to recognize and use $AUTOCONF, $AUTOMAKE, $AUTOHEADER,
-    $AUTOPOINT, $ACLOCAL and $LIBTOOLIZE
-  Fixed problem with symbols creation in Makefile.am which was assuming that
-    all versions of ccp write to standard output by default (Martin Banky). The
-    bug was introduced in libpng-1.2.9beta5.
-  Removed unused mkinstalldirs.
-
-Version 1.5.0beta49 [October 8, 2010]
-  Undid Makefile.am revision of 1.5.0beta48.
-
-Version 1.5.0beta50 [October 14, 2010]
-  Revised Makefile.in to account for mkinstalldirs being removed.
-  Added some "(unsigned long)" typecasts in printf statements in pngvalid.c.
-  Suppressed a compiler warning in png_handle_sPLT().
-  Check for out-of-range text compression mode in png_set_text().
-
-Version 1.5.0beta51 [October 15, 2010]
-  Changed embedded dates to "(PENDING RELEASE) in beta releases (and future
-    rc releases) to minimize the difference between releases.
-
-Version 1.5.0beta52 [October 16, 2010]
-  Restored some of the embedded dates (in png.h, png.c, documentation, etc.)
-
-Version 1.5.0beta53 [October 18, 2010]
-  Updated INSTALL to mention using "make maintainer-clean" and to remove
-    obsolete statement about a custom ltmain.sh
-  Disabled "color-tests" by default in Makefile.am so it will work with
-    automake versions earlier than 1.11.1
-  Use document name "libpng-manual.txt" instead of "libpng-<version>.txt"
-    to simplify version differences.
-  Removed obsolete remarks about setjmp handling from INSTALL.
-  Revised and renamed the typedef in png.h and png.c that was designed
-    to catch library and header mismatch.
-
-Version 1.5.0beta54 [November 10, 2010]
-  Require 48 bytes, not 64 bytes, for big_row_buf in overflow checks.
-  Used a consistent structure for the pngget.c functions.
-
-Version 1.5.0beta55 [November 21, 2010]
-  Revised png_get_uint_32, png_get_int_32, png_get_uint_16 (Cosmin)
-  Moved reading of file signature into png_read_sig (Cosmin)
-  Fixed atomicity of chunk header serialization (Cosmin)
-  Added test for io_state in pngtest.c (Cosmin)
-  Added "#!/bin/sh" at the top of contrib/pngminim/*/gather.sh scripts.
-  Changes to remove gcc warnings (John Bowler)
-    Certain optional gcc warning flags resulted in warnings in libpng code.
-    With these changes only -Wconversion and -Wcast-qual cannot be turned on.
-    Changes are trivial rearrangements of code.  -Wconversion is not possible
-    for pngrutil.c (because of the widespread use of += et al on variables
-    smaller than (int) or (unsigned int)) and -Wcast-qual is not possible
-    with pngwio.c and pngwutil.c because the 'write' callback and zlib
-    compression both fail to declare their input buffers with 'const'.
-
-Version 1.5.0beta56 [December 7, 2010]
-  Added the private PNG_UNUSED() macro definition in pngpriv.h.
-  Added some commentary about PNG_EXPORT in png.h and pngconf.h
-  Revised PNG_EXPORT() macro and added PNG_EXPORTA() macro, with the
-    objective of simplifying and improving the cosmetic appearance of png.h.
-  Fixed some incorrect "=" macro names in pnglibconf.dfa
-  Included documentation of changes in 1.5.0 from 1.4.x in libpng-manual.txt
-
-Version 1.5.0beta57 [December 9, 2010]
-  Documented the pngvalid gamma error summary with additional comments and
-    print statements.
-  Improved missing symbol handling in checksym.awk; symbols missing in both
-    the old and new files can now be optionally ignored, treated as errors
-    or warnings.
-  Removed references to pngvcrd.c and pnggccrd.c from the vstudio project.
-  Updated "libpng14" to "libpng15" in the visualc71 project.
-  Enabled the strip16 tests in pngvalid.`
-  Don't display test results (except PASS/FAIL) when running "make test".
-    Instead put them in pngtest-log.txt
-  Added "--with-zprefix=<string>" to configure.ac
-  Updated the prebuilt configuration files to autoconf version 2.68
-
-Version 1.5.0beta58 [December 19, 2010]
-  Fixed interlace image handling and add test cases (John Bowler)
-  Fixed the clean rule in Makefile.am to remove pngtest-log.txt
-  Made minor changes to work around warnings in gcc 3.4
-
-Version 1.5.0rc01 [December 27, 2010]
-  No changes.
-
-Version 1.5.0rc02 [December 27, 2010]
-  Eliminated references to the scripts/*.def files in project/visualc71.
-
-Version 1.5.0rc03 [December 28, 2010]
-  Eliminated scripts/*.def and revised Makefile.am accordingly
-
-Version 1.5.0rc04 [December 29, 2010]
-  Fixed bug in background transformation handling in pngrtran.c (it was
-    looking for the flag in png_ptr->transformations instead of in
-    png_ptr->flags) (David Raymond).
-
-Version 1.5.0rc05 [December 31, 2010]
-  Fixed typo in a comment in CMakeLists.txt (libpng14 => libpng15) (Cosmin)
-
-Version 1.5.0rc06 [January 4, 2011]
-  Changed the new configure option "zprefix=string" to "zlib-prefix=string"
-
-Version 1.5.0rc07 [January 4, 2011]
-  Updated copyright year.
-
-Version 1.5.0 [January 6, 2011]
-  No changes.
-
-version 1.5.1beta01 [January 8, 2011]
-  Added description of png_set_crc_action() to the manual.
-  Added a note in the manual that the type of the iCCP profile was changed
-    from png_charpp to png_bytepp in png_get_iCCP().  This change happened
-    in version 1.5.0beta36 but is not noted in the CHANGES.  Similarly,
-    it was changed from png_charpp to png_const_bytepp in png_set_iCCP().
-  Ensure that png_rgb_to_gray ignores palette mapped images, if libpng
-    internally happens to call it with one, and fixed a failure to handle
-    palette mapped images correctly.  This fixes CVE-2690.
-
-Version 1.5.1beta02 [January 14, 2011]
-  Fixed a bug in handling of interlaced images (bero at arklinux.org).
-  Updated CMakeLists.txt (Clifford Yapp)
-
-Version 1.5.1beta03 [January 14, 2011]
-  Fixed typecasting of some png_debug() statements (Cosmin)
-
-Version 1.5.1beta04 [January 16, 2011]
-  Updated documentation of png_set|get_tRNS() (Thomas Klausner).
-  Mentioned in the documentation that applications must #include "zlib.h"
-    if they need access to anything in zlib.h, and that a number of
-    macros such as png_memset() are no longer accessible by applications.
-  Corrected pngvalid gamma test "sample" function to access all of the color
-    samples of each pixel, instead of sampling the red channel three times.
-  Prefixed variable names index, div, exp, gamma with "png_" to avoid "shadow"
-    warnings, and (mistakenly) changed png_exp() to exp().
-
-Version 1.5.1beta05 [January 16, 2011]
-  Changed variable names png_index, png_div, png_exp, and png_gamma to
-    char_index, divisor, exp_b10, and gamma_val, respectively, and
-    changed exp() back to png_exp().
-
-Version 1.5.1beta06 [January 20, 2011]
-  Prevent png_push_crc_skip() from hanging while reading an unknown chunk
-    or an over-large compressed zTXt chunk with the progressive reader.
-  Eliminated more GCC "shadow" warnings.
-  Revised png_fixed() in png.c to avoid compiler warning about reaching the
-    end without returning anything.
-
-Version 1.5.1beta07 [January 22, 2011]
-  In the manual, describe the png_get_IHDR() arguments in the correct order.
-  Added const_png_structp and const_png_infop types, and used them in
-    prototypes for most png_get_*() functions.
-
-Version 1.5.1beta08 [January 23, 2011]
-  Added png_get_io_chunk_type() and deprecated png_get_io_chunk_name()
-  Added synopses for the IO_STATE functions and other missing synopses
-    to the manual. Removed the synopses from libpngpf.3 because they
-    were out of date and no longer useful.  Better information can be
-    obtained by reading the prototypes and comments in pngpriv.h
-  Attempted to fix cpp on Solaris with S. Studio 12 cc, fix build
-    Added a make macro DFNCPP that is a CPP that will accept the tokens in
-    a .dfn file and adds configure stuff to test for such a CPP.  ./configure
-    should fail if one is not available.
-  Corrected const_png_ in png.h to png_const_ to avoid polluting the namespace.
-  Added png_get_current_row_number and png_get_current_pass_number for the
-    benefit of the user transform callback.
-  Added png_process_data_pause and png_process_data_skip for the benefit of
-    progressive readers that need to stop data processing or want to optimize
-    skipping of unread data (e.g., if the reader marks a chunk to be skipped.)
-
-Version 1.5.1beta09 [January 24, 2011]
-  Enhanced pngvalid, corrected an error in gray_to_rgb, corrected doc error.
-    pngvalid contains tests of transforms, which tests are currently disabled
-    because they are incompletely tested.  gray_to_rgb was failing to expand
-    the bit depth for smaller bit depth images; this seems to be a long
-    standing error and resulted, apparently, in invalid output
-    (CVE-2011-0408, CERT VU#643140).  The documentation did not accurately
-    describe what libpng really does when converting RGB to gray.
-
-Version 1.5.1beta10 [January 27, 2010]
-  Fixed incorrect examples of callback prototypes in the manual, that were
-    introduced in libpng-1.0.0.
-  In addition the order of the png_get_uint macros with respect to the
-    relevant function definitions has been reversed.  This helps the
-    preprocessing of the symbol files be more robust.  Furthermore, the
-    symbol file preprocessing now uses -DPNG_NO_USE_READ_MACROS even when
-    the library may actually be built with PNG_USE_READ_MACROS; this stops
-    the read macros interfering with the symbol file format.
-  Made the manual, synopses, and function prototypes use the function
-    argument names file_gamma, int_file_gamma, and srgb_intent consistently.
-
-Version 1.5.1beta11 [January 28, 2011]
-  Changed PNG_UNUSED from "param=param;" to "{if(param){}}".
-  Corrected local variable type in new API png_process_data_skip()
-    The type was self-evidently incorrect but only causes problems on 64-bit
-    architectures.
-  Added transform tests to pngvalid and simplified the arguments.
-
-Version 1.5.1rc01 [January 29, 2011]
-  No changes.
-
-Version 1.5.1rc02 [January 31, 2011]
-  Added a request in the manual that applications do not use "png_" or
-    "PNG_" to begin any of their own symbols.
-  Changed PNG_UNUSED to "(void)param;" and updated the commentary in pngpriv.h
-
-Version 1.5.1 [February 3, 2011]
-  No changes.
-
-Version 1.5.2beta01 [February 13, 2011]
-  More -Wshadow fixes for older gcc compilers.  Older gcc versions apparently
-    check formal parameters names in function declarations (as well as
-    definitions) to see if they match a name in the global namespace.
-  Revised PNG_EXPORTA macro to not use an empty parameter, to accommodate the
-    old VisualC++ preprocessor.
-  Turned on interlace handling in png_read_png().
-  Fixed gcc pendantic warnings.
-  Handle longjmp in Cygwin.
-  Fixed png_get_current_row_number() in the interlaced case.
-  Cleaned up ALPHA flags and transformations.
-  Implemented expansion to 16 bits.
-
-Version 1.5.2beta02 [February 19, 2011]
-  Fixed mistake in the descriptions of user read_transform and write_transform
-    function prototypes in the manual.  The row_info struct is png_row_infop.
-  Reverted png_get_current_row_number() to previous (1.5.2beta01) behavior.
-  Corrected png_get_current_row_number documentation
-  Fixed the read/write row callback documentation.
-    This documents the current behavior, where the callback is called after
-    every row with information pertaining to the next row.
-
-Version 1.5.2beta03 [March 3, 2011]
-  Fixed scripts/makefile.vcwin32
-  Updated contrib/pngsuite/README to add the word "modify".
-  Define PNG_ALLOCATED to blank when _MSC_VER<1300.
-
-Version 1.5.2rc01 [March 19, 2011]
-  Define remaining attributes to blank when MSC_VER<1300.
-  ifdef out mask arrays in pngread.c when interlacing is not supported.
-
-Version 1.5.2rc02 [March 22, 2011]
-  Added a hint to try CPP=/bin/cpp if "cpp -E" fails in scripts/pnglibconf.mak
-    and in contrib/pngminim/*/makefile, eg., on SunOS 5.10, and removed "strip"
-    from the makefiles.
-  Fixed a bug (present since libpng-1.0.7) that makes png_handle_sPLT() fail
-    to compile when PNG_NO_POINTER_INDEXING is defined (Chubanov Kirill)
-
-Version 1.5.2rc03 [March 24, 2011]
-  Don't include standard header files in png.h while building the symbol table,
-    to avoid cpp failure on SunOS (introduced PNG_BUILDING_SYMBOL_TABLE macro).
-
-Version 1.5.2 [March 31, 2011]
-  No changes.
-
-Version 1.5.3beta01 [April 1, 2011]
-  Re-initialize the zlib compressor before compressing non-IDAT chunks.
-  Added API functions (png_set_text_compression_level() and four others) to
-    set parameters for zlib compression of non-IDAT chunks.
-
-Version 1.5.3beta02 [April 3, 2011]
-  Updated scripts/symbols.def with new API functions.
-  Only compile the new zlib re-initializing code when text or iCCP is
-    supported, using PNG_WRITE_COMPRESSED_TEXT_SUPPORTED macro.
-  Improved the optimization of the zlib CMF byte (see libpng-1.2.6beta03).
-  Optimize the zlib CMF byte in non-IDAT compressed chunks
-
-Version 1.5.3beta03 [April 16, 2011]
-  Fixed gcc -ansi -pedantic compile. A strict ANSI system does not have
-    snprintf, and the "__STRICT_ANSI__" detects that condition more reliably
-    than __STDC__ (John Bowler).
-  Removed the PNG_PTR_NORETURN attribute because it too dangerous. It tells
-    the compiler that a user supplied callback (the error handler) does not
-    return, yet there is no guarantee in practice that the application code
-    will correctly implement the error handler because the compiler only
-    issues a warning if there is a mistake (John Bowler).
-  Removed the no-longer-used PNG_DEPSTRUCT macro.
-  Updated the zlib version to 1.2.5 in the VStudio project.
-  Fixed 64-bit builds where png_uint_32 is smaller than png_size_t in
-    pngwutil.c (John Bowler).
-  Fixed bug with stripping the filler or alpha channel when writing, that
-    was introduced in libpng-1.5.2beta01 (bug report by Andrew Church).
-
-Version 1.5.3beta04 [April 27, 2011]
-  Updated pngtest.png with the new zlib CMF optimization.
-  Cleaned up conditional compilation code and of background/gamma handling
-    Internal changes only except a new option to avoid compiling the
-    png_build_grayscale_palette API (which is not used at all internally.)
-    The main change is to move the transform tests (READ_TRANSFORMS,
-    WRITE_TRANSFORMS) up one level to the caller of the APIs.  This avoids
-    calls to spurious functions if all transforms are disabled and slightly
-    simplifies those functions.  Pngvalid modified to handle this.
-    A minor change is to stop the strip_16 and expand_16 interfaces from
-    disabling each other; this allows the future alpha premultiplication
-    code to use 16-bit intermediate values while still producing 8-bit output.
-    png_do_background and png_do_gamma have been simplified to take a single
-    pointer to the png_struct rather than pointers to every item required
-    from the png_struct. This makes no practical difference to the internal
-    code.
-  A serious bug in the pngvalid internal routine 'standard_display_init' has
-    been fixed - this failed to initialize the red channel and accidentally
-    initialized the alpha channel twice.
-  Changed png_struct jmp_buf member name from png_jmpbuf to tmp_jmpbuf to
-    avoid a possible clash with the png_jmpbuf macro on some platforms.
-
-Version 1.5.3beta05 [May 6, 2011]
-  Added the "_POSIX_SOURCE" feature test macro to ensure libpng sees the
-    correct API. _POSIX_SOURCE is defined in pngpriv.h, pngtest.c and
-    pngvalid.c to ensure that POSIX conformant systems disable non-POSIX APIs.
-  Removed png_snprintf and added formatted warning messages.  This change adds
-    internal APIs to allow png_warning messages to have parameters without
-    requiring the host OS to implement snprintf.  As a side effect the
-    dependency of the tIME-supporting RFC1132 code on stdio is removed and
-    PNG_NO_WARNINGS does actually work now.
-  Pass "" instead of '\0' to png_default_error() in png_err().  This mistake
-    was introduced in libpng-1.2.20beta01.  This fixes CVE-2011-2691.
-  Added PNG_WRITE_OPTIMIZE_CMF_SUPPORTED macro to make the zlib "CMF" byte
-    optimization configureable.
-  IDAT compression failed if preceded by a compressed text chunk (bug
-    introduced in libpng-1.5.3beta01-02).  This was because the attempt to
-    reset the zlib stream in png_write_IDAT happened after the first IDAT
-    chunk had been deflated - much too late.  In this change internal
-    functions were added to claim/release the z_stream and, hopefully, make
-    the code more robust.  Also deflateEnd checking is added - previously
-    libpng would ignore an error at the end of the stream.
-
-Version 1.5.3beta06 [May 8, 2011]
-  Removed the -D_ALL_SOURCE from definitions for AIX in CMakeLists.txt
-  Implemented premultiplied alpha support: png_set_alpha_mode API
-
-Version 1.5.3beta07 [May 11, 2011]
-  Added expand_16 support to the high level interface.
-  Added named value and 'flag' gamma support to png_set_gamma.  Made a minor
-    change from the previous (unreleased) ABI/API to hide the exact value used
-    for Macs - it's not a good idea to embed this in the ABI!
-  Moved macro definitions for PNG_HAVE_IHDR, PNG_HAVE_PLTE, and PNG_AFTER_IDAT
-    from pngpriv.h to png.h because they must be visible to applications
-    that call png_set_unknown_chunks().
-  Check for up->location !PNG_AFTER_IDAT when writing unknown chunks
-    before IDAT.
-
-Version 1.5.3beta08 [May 16, 2011]
-  Improved "pngvalid --speed" to exclude more of pngvalid from the time.
-  Documented png_set_alpha_mode(), other changes in libpng.3/libpng-manual.txt
-  The cHRM chunk now sets the defaults for png_set_rgb_to_gray() (when negative
-    parameters are supplied by the caller), while in the absence of cHRM
-    sRGB/Rec 709 values are still used.  This introduced a divide-by-zero
-    bug in png_handle_cHRM().
-  The bKGD chunk no longer overwrites the background value set by
-    png_set_background(), allowing the latter to be used before the file
-    header is read. It never performed any useful function to override
-    the default anyway.
-  Added memory overwrite and palette image checks to pngvalid.c
-    Previously palette image code was poorly checked. Since the transformation
-    code has a special palette path in most cases this was a severe weakness.
-  Minor cleanup and some extra checking in pngrutil.c and pngrtran.c. When
-    expanding an indexed image, always expand to RGBA if transparency is
-    present.
-
-Version 1.5.3beta09 [May 17, 2011]
-  Reversed earlier 1.5.3 change of transformation order; move png_expand_16
-    back where it was.  The change doesn't work because it requires 16-bit
-    gamma tables when the code only generates 8-bit ones.  This fails
-    silently; the libpng code just doesn't do any gamma correction.  Moving
-    the tests back leaves the old, inaccurate, 8-bit gamma calculations, but
-    these are clearly better than none!
-
-Version 1.5.3beta10 [May 20, 2011]
-
-  png_set_background() and png_expand_16() did not work together correctly.
-    This problem is present in 1.5.2; if png_set_background is called with
-    need_expand false and the matching 16 bit color libpng erroneously just
-    treats it as an 8-bit color because of where png_do_expand_16 is in the
-    transform list.  This simple fix reduces the supplied colour to 8-bits,
-    so it gets smashed, but this is better than the current behavior.
-  Added tests for expand16, more fixes for palette image tests to pngvalid.
-    Corrects the code for palette image tests and disables attempts to
-    validate palette colors.
-
-Version 1.5.3rc01 [June 3, 2011]
-  No changes.
-
-Version 1.5.3rc02 [June 8, 2011]
-  Fixed uninitialized memory read in png_format_buffer() (Bug report by
-    Frank Busse, CVE-2011-2501, related to CVE-2004-0421).
-
-Version 1.5.3beta11 [June 11, 2011]
-  Fixed png_handle_sCAL which is broken in 1.5. This fixes CVE 2011-2692.
-  Added sCAL to pngtest.png
-  Revised documentation about png_set_user_limits() to say that it also affects
-    png writing.
-  Revised handling of png_set_user_limits() so that it can increase the
-    limit beyond the PNG_USER_WIDTH|HEIGHT_MAX; previously it could only
-    reduce it.
-  Make the 16-to-8 scaling accurate. Dividing by 256 with no rounding is
-    wrong (high by one) 25% of the time. Dividing by 257 with rounding is
-    wrong in 128 out of 65536 cases. Getting the right answer all the time
-    without division is easy.
-  Added "_SUPPORTED" to the PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION macro.
-  Added projects/owatcom, an IDE project for OpenWatcom to replace
-    scripts/makefile.watcom.  This project works with OpenWatcom 1.9. The
-    IDE autogenerates appropriate makefiles (libpng.mk) for batch processing.
-    The project is configurable, unlike the Visual Studio project, so long
-    as the developer has an awk.
-  Changed png_set_gAMA to limit the gamma value range so that the inverse
-    of the stored value cannot overflow the fixed point representation,
-    and changed other things OpenWatcom warns about.
-  Revised pngvalid.c to test PNG_ALPHA_MODE_SUPPORTED correctly. This allows
-    pngvalid to build when ALPHA_MODE is not supported, which is required if
-    it is to build on libpng 1.4.
-  Removed string/memory macros that are no longer used and are not
-    necessarily fully supportable, particularly png_strncpy and png_snprintf.
-  Added log option to pngvalid.c and attempted to improve gamma messages.
-
-Version 1.5.3 [omitted]
-  People found the presence of a beta release following an rc release
-    to be confusing; therefore we bump the version to libpng-1.5.4beta01
-    and there will be no libpng-1.5.3 release.
-
-Version 1.5.4beta01 [June 14, 2011]
-  Made it possible to undefine PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
-    to get the same (inaccurate) output as libpng-1.5.2 and earlier.
-  Moved definitions of PNG_HAVE_IHDR, PNG_AFTER_IDAT, and PNG_HAVE_PLTE
-    outside of an unknown-chunk block in png.h because they are also
-    needed for other uses.
-
-Version 1.5.4beta02 [June 14, 2011]
-  Fixed and clarified LEGACY 16-to-8 scaling code.
-  Added png_set_chop_16() API, to match inaccurate results from previous
-    libpng versions.
-  Removed the ACCURATE and LEGACY options (they are no longer useable)
-  Use the old scaling method for background if png_set_chop_16() was
-    called.
-  Made png_set_chop_16() API removeable by disabling PNG_CHOP_16_TO_8_SUPPORTED
-
-Version 1.5.4beta03 [June 15, 2011]
-  Fixed a problem in png_do_expand_palette() exposed by optimization in
-    1.5.3beta06
-  Also removed a spurious and confusing "trans" member ("trans") from png_info.
-  The palette expand optimization prevented expansion to an intermediate RGBA
-    form if tRNS was present but alpha was marked to be stripped; this exposed
-    a check for tRNS in png_do_expand_palette() which is inconsistent with the
-    code elsewhere in libpng.
-  Correction to the expand_16 code; removed extra instance of
-    png_set_scale_16_to_8 from pngpriv.h
-
-Version 1.5.4beta04 [June 16, 2011]
-  Added a missing "#ifdef PNG_READ_BACKGROUND_SUPPORTED/#endif" in pngrtran.c
-  Added PNG_TRANSFORM_CHOP_16 to the high-level read transforms.
-  Made PNG_READ_16_TO_8_ACCURATE_SCALE configurable again.  If this is
-    not enabled, png_set_strip_16() and png_do_scale_16_to_8() aren't built.
-  Revised contrib/visupng, gregbook, and pngminim to demonstrate chop_16_to_8
-
-Version 1.5.4beta05 [June 16, 2011]
-  Renamed png_set_strip_16() to png_set_scale_16() and renamed
-    png_set_chop_16() to png_set_strip(16) in an attempt to minimize the
-    behavior changes between libpng14 and libpng15.
-
-Version 1.5.4beta06 [June 18, 2011]
-  Fixed new bug that was causing both strip_16 and scale_16 to be applied.
-
-Version 1.5.4beta07 [June 19, 2011]
-  Fixed pngvalid, simplified macros, added checking for 0 in sCAL.
-    The ACCURATE scale macro is no longer defined in 1.5 - call the
-    png_scale_16_to_8 API.  Made sure that PNG_READ_16_TO_8 is still defined
-    if the png_strip_16_to_8 API is present.  png_check_fp_number now
-    maintains some state so that positive, negative and zero values are
-    identified.  sCAL uses these to be strictly spec conformant.
-
-Version 1.5.4beta08 [June 23, 2011]
-  Fixed pngvalid if ACCURATE_SCALE is defined.
-  Updated scripts/pnglibconf.h.prebuilt.
-
-Version 1.5.4rc01 [June 30, 2011]
-  Define PNG_ALLOCATED to "restrict" only if MSC_VER >= 1400.
-
-Version 1.5.4 [July 7, 2011]
-  No changes.
-
-Version 1.5.5beta01 [July 13, 2011]
-  Fixed some typos and made other minor changes in the manual.
-  Updated contrib/pngminus/makefile.std (Samuli Souminen)
-
-Version 1.5.5beta02 [July 14, 2011]
-  Revised Makefile.am and Makefile.in to look in the right directory for
-    pnglibconf.h.prebuilt
-
-Version 1.5.5beta03 [July 27, 2011]
-  Enabled compilation with g++ compiler.  This compiler does not recognize
-    the file extension, so it always compiles with C++ rules.  Made minor
-    changes to pngrutil.c to cast results where C++ expects it but C does not.
-  Minor editing of libpng.3 and libpng-manual.txt.
-
-Version 1.5.5beta04 [July 29, 2011]
-  Revised CMakeLists.txt (Clifford Yapp)
-  Updated commentary about the png_rgb_to_gray() default coefficients
-    in the manual and in pngrtran.c
-
-Version 1.5.5beta05 [August 17, 2011]
-  Prevent unexpected API exports from non-libpng DLLs on Windows.  The "_DLL"
-    is removed from the test of whether a DLL is being built (this erroneously
-    caused the libpng APIs to be marked as DLL exports in static builds under
-    Microsoft Visual Studio).  Almost all of the libpng building configuration
-    is moved from pngconf.h to pngpriv.h, but PNG_DLL_EXPORT remains in
-    pngconf.h, though, so that it is colocated with the import definition (it
-    is no longer used anywhere in the installed headers).  The VStudio project
-    definitions have been cleaned up: "_USRDLL" has been removed from the
-    static library builds (this was incorrect), and PNG_USE_DLL has been added
-    to pngvalid to test the functionality (pngtest does not supply it,
-    deliberately).  The spurious "_EXPORTS" has been removed from the
-    libpng build (all these errors were a result of copy/paste between project
-    configurations.)
-  Added new types and internal functions for CIE RGB end point handling to
-    pngpriv.h (functions yet to be implemented).
-
-Version 1.5.5beta06 [August 26, 2011]
-  Ensure the CMAKE_LIBRARY_OUTPUT_DIRECTORY is set in CMakeLists.txt
-    (Clifford Yap)
-  Fixes to rgb_to_gray and cHRM XYZ APIs (John Bowler):
-    The rgb_to_gray code had errors when combined with gamma correction.
-    Some pixels were treated as true grey when they weren't and such pixels
-    and true grey ones were not gamma corrected (the original value of the
-    red component was used instead).  APIs to get and set cHRM using color
-    space end points have been added and the rgb_to_gray code that defaults
-    based on cHRM, and the divide-by-zero bug in png_handle_cHRM (CERT
-    VU#477046, CVE-2011-3328, introduced in 1.5.4) have been corrected.
-  A considerable number of tests has been added to pngvalid for the
-    rgb_to_gray transform.
-  Arithmetic errors in rgb_to_gray whereby the calculated gray value was
-    truncated to the bit depth rather than rounded have been fixed except in
-    the 8-bit non-gamma-corrected case (where consistency seems more important
-    than correctness.)  The code still has considerable inaccuracies in the
-    8-bit case because 8-bit linear arithmetic is used.
-
-Version 1.5.5beta07 [September 7, 2011]
-  Added "$(ARCH)" option to makefile.darwin
-  Added SunOS support to configure.ac and Makefile.am
-  Changed png_chunk_benign_error() to png_warning() in png.c, in
-    png_XYZ_from_xy_checked().
-
-Version 1.5.5beta08 [September 10, 2011]
-  Fixed 64-bit compilation errors (gcc). The errors fixed relate
-    to conditions where types that are 32 bits in the GCC 32-bit
-    world (uLong and png_size_t) become 64 bits in the 64-bit
-    world.  This produces potential truncation errors which the
-    compiler correctly flags.
-  Relocated new HAVE_SOLARIS_LD definition in configure.ac
-  Constant changes for 64-bit compatibility (removal of L suffixes). The
-    16-bit cases still use "L" as we don't have a 16-bit test system.
-
-Version 1.5.5rc01 [September 15, 2011]
-  Removed "L" suffixes in pngpriv.h
-
-Version 1.5.5 [September 22, 2011]
-  No changes.
-
-Version 1.5.6beta01 [September 22, 2011]
-  Fixed some 64-bit type conversion warnings in pngrtran.c
-  Moved row_info from png_struct to a local variable.
-  The various interlace mask arrays have been made into arrays of
-    bytes and made PNG_CONST and static (previously some arrays were
-    marked PNG_CONST and some weren't).
-  Additional checks have been added to the transform code to validate the
-    pixel depths after the transforms on both read and write.
-  Removed some redundant code from pngwrite.c, in png_destroy_write_struct().
-  Changed chunk reading/writing code to use png_uint_32 instead of png_byte[4].
-    This removes the need to allocate temporary strings for chunk names on
-    the stack in the read/write code.  Unknown chunk handling still uses the
-    string form because this is exposed in the API.
-
-Version 1.5.6beta02 [September 26, 2011]
-  Added a note in the manual the png_read_update_info() must be called only
-    once with a particular info_ptr.
-  Fixed a typo in the definition of the new PNG_STRING_FROM_CHUNK(s,c) macro.
-
-Version 1.5.6beta03 [September 28, 2011]
-  Revised test-pngtest.sh to report FAIL when pngtest fails.
-  Added "--strict" option to pngtest, to report FAIL when the failure is
-    only because the resulting valid files are different.
-  Revised CMakeLists.txt to work with mingw and removed some material from
-    CMakeLists.txt that is no longer useful in libpng-1.5.
-
-Version 1.5.6beta04 [October 5, 2011]
-  Fixed typo in Makefile.in and Makefile.am ("-M Wl" should be "-M -Wl")."
-
-Version 1.5.6beta05 [October 12, 2011]
-  Speed up png_combine_row() for interlaced images. This reduces the generality
-    of the code, allowing it to be optimized for Adam7 interlace.  The masks
-    passed to png_combine_row() are now generated internally, avoiding
-    some code duplication and localizing the interlace handling somewhat.
-  Align png_struct::row_buf - previously it was always unaligned, caused by
-    a bug in the code that attempted to align it; the code needs to subtract
-    one from the pointer to take account of the filter byte prepended to
-    each row.
-  Optimized png_combine_row() when rows are aligned. This gains a small
-    percentage for 16-bit and 32-bit pixels in the typical case where the
-    output row buffers are appropriately aligned. The optimization was not
-    previously possible because the png_struct buffer was always misaligned.
-  Fixed bug in png_write_chunk_header() debug print, introduced in 1.5.6beta01.
-
-Version 1.5.6beta06 [October 17, 2011]
-  Removed two redundant tests for unitialized row.
-  Fixed a relatively harmless memory overwrite in compressed text writing
-    with a 1 byte zlib buffer.
-  Add ability to call png_read_update_info multiple times to pngvalid.c.
-  Fixes for multiple calls to png_read_update_info. These fixes attend to
-    most of the errors revealed in pngvalid, however doing the gamma work
-    twice results in inaccuracies that can't be easily fixed.  There is now
-    a warning in the code if this is going to happen.
-  Turned on multiple png_read_update_info in pngvalid transform tests.
-  Prevent libpng from overwriting unused bits at the end of the image when
-    it is not byte aligned, while reading. Prior to libpng-1.5.6 libpng would
-    overwrite the partial byte at the end of each row if the row width was not
-    an exact multiple of 8 bits and the image is not interlaced.
-
-Version 1.5.6beta07 [October 21, 2011]
-  Made png_ptr->prev_row an aligned pointer into png_ptr->big_prev_row
-    (Mans Rullgard).
-
-Version 1.5.6rc01 [October 26, 2011]
-  Changed misleading "Missing PLTE before cHRM" warning to "Out of place cHRM"
-
-Version 1.5.6rc02 [October 27, 2011]
-  Added LSR() macro to defend against buggy compilers that evaluate non-taken
-    code branches and complain about out-of-range shifts.
-
-Version 1.5.6rc03 [October 28, 2011]
-  Renamed the LSR() macro to PNG_LSR() and added PNG_LSL() macro.
-  Fixed compiler warnings with Intel and MSYS compilers. The logical shift
-    fix for Microsoft Visual C is required by other compilers, so this
-    enables that fix for all compilers when using compile-time constants.
-    Under MSYS 'byte' is a name declared in a system header file, so we
-    changed the name of a local variable to avoid the warnings that result.
-  Added #define PNG_ALIGN_TYPE PNG_ALIGN_NONE to contrib/pngminim/*/pngusr.h
-
-Version 1.5.6 [November 3, 2011]
-  No changes.
-
-Version 1.5.7beta01 [November 4, 2011]
-  Added support for ARM processor, when decoding all PNG up-filtered rows
-    and any other-filtered rows with 3 or 4 bytes per pixel (Mans Rullgard).
-  Fixed bug in pngvalid on early allocation failure; fixed type cast in
-    pngmem.c; pngvalid would attempt to call png_error() if the allocation
-    of a png_struct or png_info failed. This would probably have led to a
-    crash.  The pngmem.c implementation of png_malloc() included a cast
-    to png_size_t which would fail on large allocations on 16-bit systems.
-  Fix for the preprocessor of the Intel C compiler. The preprocessor
-    splits adjacent @ signs with a space; this changes the concatentation
-    token from @-@-@ to PNG_JOIN; that should work with all compiler
-    preprocessors.
-  Paeth filter speed improvements from work by Siarhei Siamashka. This
-    changes the 'Paeth' reconstruction function to improve the GCC code
-    generation on x86. The changes are only part of the suggested ones;
-    just the changes that definitely improve speed and remain simple.
-    The changes also slightly increase the clarity of the code.
-
-Version 1.5.7beta02 [November 11, 2011]
-  Check compression_type parameter in png_get_iCCP and remove spurious
-    casts. The compression_type parameter is always assigned to, so must
-    be non-NULL. The cast of the profile length potentially truncated the
-    value unnecessarily on a 16-bit int system, so the cast of the (byte)
-    compression type to (int) is specified by ANSI-C anyway.
-  Fixed FP division by zero in pngvalid.c; the 'test_pixel' code left
-    the sBIT fields in the test pixel as 0, which resulted in a floating
-    point division by zero which was irrelevant but causes systems where
-    FP exceptions cause a crash. Added code to pngvalid to turn on FP
-    exceptions if the appropriate glibc support is there to ensure this is
-    tested in the future.
-  Updated scripts/pnglibconf.mak and scripts/makefile.std to handle the
-    new PNG_JOIN macro.
-  Added versioning to pnglibconf.h comments.
-  Simplified read/write API initial version; basic read/write tested on
-    a variety of images, limited documentation (in the header file.)
-  Installed more accurate linear to sRGB conversion tables. The slightly
-    modified tables reduce the number of 16-bit values that
-    convert to an off-by-one 8-bit value.  The "makesRGB.c" code that was used
-    to generate the tables is now in a contrib/sRGBtables sub-directory.
-
-Version 1.5.7beta03 [November 17, 2011]
-  Removed PNG_CONST from the sRGB table declarations in pngpriv.h and png.c
-  Added run-time detection of NEON support.
-  Added contrib/libtests; includes simplified API test and timing test and
-    a color conversion utility for rapid checking of failed 'pngstest' results.
-  Multiple transform bug fixes plus a work-round for double gamma correction.
-    libpng does not support more than one transform that requires linear data
-    at once - if this is tried typically the results is double gamma
-    correction. Since the simplified APIs can need rgb to gray combined with
-    a compose operation it is necessary to do one of these outside the main
-    libpng transform code. This check-in also contains fixes to various bugs
-    in the simplified APIs themselves and to some bugs in compose and rgb to
-    gray (on palette) itself.
-  Fixes for C++ compilation using g++ When libpng source is compiled
-    using g++. The compiler imposes C++ rules on the C source; thus it
-    is desireable to make the source work with either C or C++ rules
-    without throwing away useful error information.  This change adds
-    png_voidcast to allow C semantic (void*) cases or the corresponding
-    C++ static_cast operation, as appropriate.
-  Added --noexecstack to assembler file compilation. GCC does not set
-    this on assembler compilation, even though it does on C compilation.
-    This creates security issues if assembler code is enabled; the
-    work-around is to set it by default in the flags for $(CCAS)
-  Work around compilers that don't support declaration of const data. Some
-    compilers fault 'extern const' data declarations (because the data is
-    not initialized); this turns on const-ness only for compilers where
-    this is known to work.
-
-Version 1.5.7beta04 [November 17, 2011]
-  Since the gcc driver does not recognize the --noexecstack flag, we must
-    use the -Wa prefix to have it passed through to the assembler.
-    Also removed a duplicate setting of this flag.
-  Added files that were omitted from the libpng-1.5.7beta03 zip distribution.
-
-Version 1.5.7beta05 [November 25, 2011]
-  Removed "zTXt" from warning in generic chunk decompression function.
-  Validate time settings passed to png_set_tIME() and png_convert_to_rfc1123()
-    (Frank Busse). Note: This prevented CVE-2015-7981 from affecting
-    libpng-1.5.7 and later.
-  Added MINGW support to CMakeLists.txt
-  Reject invalid compression flag or method when reading the iTXt chunk.
-  Backed out 'simplified' API changes. The API seems too complex and there
-    is a lack of consensus or enthusiasm for the proposals.  The API also
-    reveals significant bugs inside libpng (double gamma correction and the
-    known bug of being unable to retrieve a corrected palette). It seems
-    better to wait until the bugs, at least, are corrected.
-  Moved pngvalid.c into contrib/libtests
-  Rebuilt Makefile.in, configure, etc., with autoconf-2.68
-
-Version 1.5.7rc01 [December 1, 2011]
-  Replaced an "#if" with "#ifdef" in pngrtran.c
-  Revised #if PNG_DO_BC block in png.c (use #ifdef and add #else)
-
-Version 1.5.7rc02 [December 5, 2011]
-  Revised project files and contrib/pngvalid/pngvalid.c to account for
-    the relocation of pngvalid into contrib/libtests.
-  Revised pngconf.h to use " __declspec(restrict)" only when MSC_VER >= 1400,
-    as in libpng-1.5.4.
-  Put CRLF line endings in the owatcom project files.
-
-Version 1.5.7rc03 [December 7, 2011]
-  Updated CMakeLists.txt to account for the relocation of pngvalid.c
-
-Version 1.5.7 [December 15, 2011]
-  Minor fixes to pngvalid.c for gcc 4.6.2 compatibility to remove warnings
-    reported by earlier versions.
-  Fixed minor memset/sizeof errors in pngvalid.c.
-
-Version 1.6.0beta01 [December 15, 2011]
-  Removed machine-generated configure files from the GIT repository (they will
-    continue to appear in the tarball distributions and in the libpng15 and
-    earlier GIT branches).
-  Restored the new 'simplified' API, which was started in libpng-1.5.7beta02
-    but later deleted from libpng-1.5.7beta05.
-  Added example programs for the new 'simplified' API.
-  Added ANSI-C (C90) headers and require them, and take advantage of the
-    change. Also fixed some of the projects/* and contrib/* files that needed
-    updates for libpng16 and the move of pngvalid.c.
-    With this change the required ANSI-C header files are assumed to exist: the
-    implementation must provide float.h, limits.h, stdarg.h and stddef.h and
-    libpng relies on limits.h and stddef.h existing and behaving as defined
-    (the other two required headers aren't used).  Non-ANSI systems that don't
-    have stddef.h or limits.h will have to provide an appropriate fake
-    containing the relevant types and #defines.
-  Dropped support for 16-bit platforms. The use of FAR/far has been eliminated
-    and the definition of png_alloc_size_t is now controlled by a flag so
-    that 'small size_t' systems can select it if necessary.  Libpng 1.6 may
-    not currently work on such systems -- it seems likely that it will
-    ask 'malloc' for more than 65535 bytes with any image that has a
-    sufficiently large row size (rather than simply failing to read such
-    images).
-  New tools directory containing tools used to generate libpng code.
-  Fixed race conditions in parallel make builds. With higher degrees of
-    parallelism during 'make' the use of the same temporary file names such
-    as 'dfn*' can result in a race where a temporary file from one arm of the
-    build is deleted or overwritten in another arm.  This changes the
-    temporary files for suffix rules to always use $* and ensures that the
-    non-suffix rules use unique file names.
-
-Version 1.6.0beta02 [December 21, 2011]
-  Correct configure builds where build and source directories are separate.
-    The include path of 'config.h' was erroneously made relative in pngvalid.c
-    in libpng 1.5.7.
-
-Version 1.6.0beta03 [December 22, 2011]
-  Start-up code size improvements, error handler flexibility. These changes
-    alter how the tricky allocation of the initial png_struct and png_info
-    structures are handled. png_info is now handled in pretty much the same
-    way as everything else, except that the allocations handle NULL return
-    silently.  png_struct is changed in a similar way on allocation and on
-    deallocation a 'safety' error handler is put in place (which should never
-    be required).  The error handler itself is changed to permit mismatches
-    in the application and libpng error buffer size; however, this means a
-    silent change to the API to return the jmp_buf if the size doesn't match
-    the size from the libpng compilation; libpng now allocates the memory and
-    this may fail.  Overall these changes result in slight code size
-    reductions; however, this is a reduction in code that is always executed
-    so is particularly valuable.  Overall on a 64-bit system the libpng DLL
-    decreases in code size by 1733 bytes.  pngerror.o increases in size by
-    about 465 bytes because of the new functionality.
-  Added png_convert_to_rfc1123_buffer() and deprecated png_convert_to_rfc1123()
-    to avoid including a spurious buffer in the png_struct.
-
-Version 1.6.0beta04 [December 30, 2011]
-  Regenerated configure scripts with automake-1.11.2
-  Eliminated png_info_destroy(). It is now used only in png.c and only calls
-    one other internal function and memset().
-  Enabled png_get_sCAL_fixed() if floating point APIs are enabled. Previously
-    it was disabled whenever internal fixed point arithmetic was selected,
-    which meant it didn't exist even on systems where FP was available but not
-    preferred.
-  Added pngvalid.c compile time checks for const APIs.
-  Implemented 'restrict' for png_info and png_struct. Because of the way
-    libpng works both png_info and png_struct are always accessed via a
-    single pointer.  This means adding C99 'restrict' to the pointer gives
-    the compiler some opportunity to optimize the code.  This change allows
-    that.
-  Moved AC_MSG_CHECKING([if libraries can be versioned]) later to the proper
-    location in configure.ac (Gilles Espinasse).
-  Changed png_memcpy to C assignment where appropriate. Changed all those
-    uses of png_memcpy that were doing a simple assignment to assignments
-    (all those cases where the thing being copied is a non-array C L-value).
-  Added some error checking to png_set_*() routines.
-  Removed the reference to the non-exported function png_memcpy() from
-    example.c.
-  Fixed the Visual C 64-bit build - it requires jmp_buf to be aligned, but
-    it had become misaligned.
-  Revised contrib/pngminus/pnm2png.c to avoid warnings when png_uint_32
-    and unsigned long are of different sizes.
-
-Version 1.6.0beta05 [January 15, 2012]
-  Updated manual with description of the simplified API (copied from png.h)
-  Fix bug in pngerror.c: some long warnings were being improperly truncated
-    (CVE-2011-3464, bug introduced in libpng-1.5.3beta05).
-
-Version 1.6.0beta06 [January 24, 2012]
-  Added palette support to the simplified APIs. This commit
-    changes some of the macro definitions in png.h, app code
-    may need corresponding changes.
-  Increased the formatted warning buffer to 192 bytes.
-  Added color-map support to simplified API. This is an initial version for
-    review; the documentation has not yet been updated.
-  Fixed Min/GW uninstall to remove libpng.dll.a
-
-Version 1.6.0beta07 [January 28, 2012]
-  Eliminated Intel icc/icl compiler warnings. The Intel (GCC derived)
-    compiler issues slightly different warnings from those issued by the
-    current vesions of GCC. This eliminates those warnings by
-    adding/removing casts and small code rewrites.
-  Updated configure.ac from autoupdate: added --enable-werror option.
-    Also some layout regularization and removal of introduced tab characters
-    (replaced with 3-character indentation).  Obsolete macros identified by
-    autoupdate have been removed; the replacements are all in 2.59 so
-    the pre-req hasn't been changed.  --enable-werror checks for support
-    for -Werror (or the given argument) in the compiler.  This mimics the
-    gcc configure option by allowing -Werror to be turned on safely; without
-    the option the tests written in configure itself fail compilation because
-    they cause compiler warnings.
-  Rewrote autogen.sh to run autoreconf instead of running tools one-by-one.
-  Conditionalize the install rules for MINGW and CYGWIN in CMakeLists.txt and
-    set CMAKE_LIBRARY_OUTPUT_DIRECTORY to "lib" on all platforms (C. Yapp).
-  Freeze libtool files in the 'scripts' directory. This version of autogen.sh
-    attempts to dissuade people from running it when it is not, or should not,
-    be necessary.  In fact, autogen.sh does not work when run in a libpng
-    directory extracted from a tar distribution anymore. You must run it in
-    a GIT clone instead.
-  Added two images to contrib/pngsuite (1-bit and 2-bit transparent grayscale),
-    and renamed three whose names were inconsistent with those in
-    pngsuite/README.txt.
-
-Version 1.6.0beta08 [February 1, 2012]
-  Fixed Image::colormap misalignment in pngstest.c
-  Check libtool/libtoolize version number (2.4.2) in configure.ac
-  Divide test-pngstest.sh into separate pngstest runs for basic and
-    transparent images.
-  Moved automake options to AM_INIT_AUTOMAKE in configure.ac
-  Added color-tests, silent-rules (Not yet implemented in Makefile.am) and
-    version checking to configure.ac
-  Improved pngstest speed by not doing redundant tests and add const to
-    the background parameter of png_image_finish_read. The --background
-    option is now done automagically only when required, so that commandline
-    option no longer exists.
-  Cleaned up pngpriv.h to consistently declare all functions and data.
-    Also eliminated PNG_CONST_DATA, which is apparently not needed but we
-    can't be sure until it is gone.
-  Added symbol prefixing that allows all the libpng external symbols
-    to be prefixed (suggested by Reuben Hawkins).
-  Updated "ftbb*.png" list in the owatcom and vstudio projects.
-  Fixed 'prefix' builds on clean systems. The generation of pngprefix.h
-    should not require itself.
-  Updated INSTALL to explain that autogen.sh must be run in a GIT clone,
-    not in a libpng directory extracted from a tar distribution.
-
-Version 1.6.0beta09 [February 1, 2012]
-  Reverted the prebuilt configure files to libpng-1.6.0beta05 condition.
-
-Version 1.6.0beta10 [February 3, 2012]
-  Added Z_SOLO for zlib-1.2.6+ and correct pngstest tests
-  Updated list of test images in CMakeLists.txt
-  Updated the prebuilt configure files to current condition.
-  Revised INSTALL information about autogen.sh; it works in tar distributions.
-
-Version 1.6.0beta11 [February 16, 2012]
-  Fix character count in pngstest command in projects/owatcom/pngstest.tgt
-  Revised test-pngstest.sh to report PASS/FAIL for each image.
-  Updated documentation about the simplified API.
-  Corrected estimate of error in libpng png_set_rgb_to_gray API.  The API is
-    extremely inaccurate for sRGB conversions because it uses an 8-bit
-    intermediate linear value and it does not use the sRGB transform, so it
-    suffers from the known instability in gamma transforms for values close
-    to 0 (see Poynton).  The net result is that the calculation has a maximum
-    error of 14.99/255; 0.5/255^(1/2.2).  pngstest now uses 15 for the
-    permitted 8-bit error. This may still not be enough because of arithmetic
-    error.
-  Removed some unused arrays (with #ifdef) from png_read_push_finish_row().
-  Fixed a memory overwrite bug in simplified read of RGB PNG with
-    non-linear gamma Also bugs in the error checking in pngread.c and changed
-    quite a lot of the checks in pngstest.c to be correct; either correctly
-    written or not over-optimistic.  The pngstest changes are insufficient to
-    allow all possible RGB transforms to be passed; pngstest cmppixel needs
-    to be rewritten to make it clearer which errors it allows and then changed
-    to permit known inaccuracies.
-  Removed tests for no-longer-used *_EMPTY_PLTE_SUPPORTED from pngstruct.h
-  Fixed fixed/float API export conditionals. 1) If FIXED_POINT or
-    FLOATING_POINT options were switched off, png.h ended up with lone ';'
-    characters.  This is not valid ANSI-C outside a function.  The ';'
-    characters have been moved inside the definition of PNG_FP_EXPORT and
-    PNG_FIXED_EXPORT. 2) If either option was switched off, the declaration
-    of the corresponding functions were completely omitted, even though some
-    of them are still used internally.  The result is still valid, but
-    produces warnings from gcc with some warning options (including -Wall). The
-    fix is to cause png.h to declare the functions with PNG_INTERNAL_FUNCTION
-    when png.h is included from pngpriv.h.
-  Check for invalid palette index while reading paletted PNG.  When one is
-    found, issue a warning and increase png_ptr->num_palette accordingly.
-    Apps are responsible for checking to see if that happened.
-
-Version 1.6.0beta12 [February 18, 2012]
-  Do not increase num_palette on invalid_index.
-  Relocated check for invalid palette index to pngrtran.c, after unpacking
-    the sub-8-bit pixels.
-  Fixed CVE-2011-3026 buffer overrun bug.  This bug was introduced when
-    iCCP chunk support was added at libpng-1.0.6. Deal more correctly with the
-    test on iCCP chunk length. Also removed spurious casts that may hide
-    problems on 16-bit systems.
-
-Version 1.6.0beta13 [February 24, 2012]
-  Eliminated redundant png_push_read_tEXt|zTXt|iTXt|unknown code from
-    pngpread.c and use the sequential png_handle_tEXt, etc., in pngrutil.c;
-    now that png_ptr->buffer is inaccessible to applications, the special
-    handling is no longer useful.
-  Added PNG_SAFE_LIMITS feature to pnglibconf.dfa, pngpriv.h, and new
-    pngusr.dfa to reset the user limits to safe ones if PNG_SAFE_LIMITS is
-    defined.  To enable, use "CPPFLAGS=-DPNG_SAFE_LIMITS_SUPPORTED=1" on the
-    configure command or put #define PNG_SAFE_LIMITS_SUPPORTED in
-    pnglibconf.h.prebuilt and pnglibconf.h.
-
-Version 1.6.0beta14 [February 27, 2012]
-  Added information about the new limits in the manual.
-  Updated Makefile.in
-
-Version 1.6.0beta15 [March 2, 2012]
-  Removed unused "current_text" members of png_struct and the png_free()
-    of png_ptr->current_text from pngread.c
-  Rewrote pngstest.c for substantial speed improvement.
-  Fixed transparent pixel and 16-bit rgb tests in pngstest and removed a
-    spurious check in pngwrite.c
-  Added PNG_IMAGE_FLAG_FAST for the benefit of applications that store
-    intermediate files, or intermediate in-memory data, while processing
-    image data with the simplified API.  The option makes the files larger
-    but faster to write and read.  pngstest now uses this by default; this
-    can be disabled with the --slow option.
-  Improved pngstest fine tuning of error numbers, new test file generator.
-    The generator generates images that test the full range of sample values,
-    allow the error numbers in pngstest to be tuned and checked.  makepng
-    also allows generation of images with extra chunks, although this is
-    still work-in-progress.
-  Added check for invalid palette index while reading.
-  Fixed some bugs in ICC profile writing. The code should now accept
-    all potentially valid ICC profiles and reject obviously invalid ones.
-    It now uses png_error() to do so rather than casually writing a PNG
-    without the necessary color data.
-  Removed whitespace from the end of lines in all source files and scripts.
-
-Version 1.6.0beta16 [March 6, 2012]
-  Relocated palette-index checking function from pngrutil.c to pngtrans.c
-  Added palette-index checking while writing.
-  Changed png_inflate() and calling routines to avoid overflow problems.
-    This is an intermediate check-in that solves the immediate problems and
-    introduces one performance improvement (avoiding a copy via png_ptr->zbuf.)
-    Further changes will be made to make ICC profile handling more secure.
-  Fixed build warnings (MSVC, GCC, GCC v3). Cygwin GCC with default options
-    declares 'index' as a global, causing a warning if it is used as a local
-    variable.  GCC 64-bit warns about assigning a (size_t) (unsigned 64-bit)
-    to an (int) (signed 32-bit).  MSVC, however, warns about using the
-    unary '-' operator on an unsigned value (even though it is well defined
-    by ANSI-C to be ~x+1).  The padding calculation was changed to use a
-    different method.  Removed the tests on png_ptr->pass.
-  Added contrib/libtests/tarith.c to test internal arithmetic functions from
-    png.c. This is a libpng maintainer program used to validate changes to the
-    internal arithmetic functions.
-  Made read 'inflate' handling like write 'deflate' handling. The read
-    code now claims and releases png_ptr->zstream, like the write code.
-    The bug whereby the progressive reader failed to release the zstream
-    is now fixed, all initialization is delayed, and the code checks for
-    changed parameters on deflate rather than always calling
-    deflatedEnd/deflateInit.
-  Validate the zTXt strings in pngvalid.
-  Added code to validate the windowBits value passed to deflateInit2().
-    If the call to deflateInit2() is wrong a png_warning will be issued
-    (in fact this is harmless, but the PNG data produced may be sub-optimal).
-
-Version 1.6.0beta17 [March 10, 2012]
-  Fixed PNG_LIBPNG_BUILD_BASE_TYPE definition. 
-  Reject all iCCP chunks after the first, even if the first one is invalid.
-  Deflate/inflate was reworked to move common zlib calls into single
-    functions [rw]util.c.  A new shared keyword check routine was also added
-    and the 'zbuf' is no longer allocated on progressive read.  It is now
-    possible to call png_inflate() incrementally.  A warning is no longer
-    issued if the language tag or translated keyword in the iTXt chunk
-    has zero length.
-  If benign errors are disabled use maximum window on ancilliary inflate.
-    This works round a bug introduced in 1.5.4 where compressed ancillary
-    chunks could end up with a too-small windowBits value in the deflate
-    header.
-
-Version 1.6.0beta18 [March 16, 2012]
-  Issue a png_benign_error() instead of png_warning() about bad palette index.
-  In pngtest, treat benign errors as errors if "-strict" is present.
-  Fixed an off-by-one error in the palette index checking function.
-  Fixed a compiler warning under Cygwin (Windows-7, 32-bit system)
-  Revised example.c to put text strings in a temporary character array
-    instead of directly assigning string constants to png_textp members.
-    This avoids compiler warnings when -Wwrite-strings is enabled.
-  Added output flushing to aid debugging under Visual Studio. Unfortunately
-    this is necessary because the VS2010 output window otherwise simply loses
-    the error messages on error (they weren't flushed to the window before
-    the process exited, apparently!)
-  Added configuration support for benign errors and changed the read
-    default. Also changed some warnings in the iCCP and sRGB handling
-    from to benign errors. Configuration now makes read benign
-    errors warnings and write benign errors to errors by default (thus
-    changing the behavior on read).  The simplified API always forces
-    read benign errors to warnings (regardless of the system default, unless
-    this is disabled in which case the simplified API can't be built.)
-
-Version 1.6.0beta19 [March 18, 2012]
-  Work around for duplicate row start calls; added warning messages.
-    This turns on PNG_FLAG_DETECT_UNINITIALIZED to detect app code that
-    fails to call one of the 'start' routines (not enabled in libpng-1.5
-    because it is technically an API change, since it did normally work
-    before.)  It also makes duplicate calls to png_read_start_row (an
-    internal function called at the start of the image read) benign, as
-    they were before changes to use png_inflate_claim. Somehow webkit is
-    causing this to happen; this is probably a mis-feature in the zlib
-    changes so this commit is only a work-round.
-  Removed erroneous setting of DETECT_UNINITIALIZED and added more
-    checks. The code now does a png_error if an attempt is made to do the
-    row initialization twice; this is an application error and it has
-    serious consequences because the transform data in png_struct is
-    changed by each call.
-  Added application error reporting and added chunk names to read
-    benign errors; also added --strict to pngstest - not enabled
-    yet because a warning is produced.
-  Avoid the double gamma correction warning in the simplified API.
-    This allows the --strict option to pass in the pngstest checks
-
-Version 1.6.0beta20 [March 29, 2012]
-  Changed chunk handler warnings into benign errors, incrementally load iCCP
-  Added checksum-icc.c to contrib/tools
-  Prevent PNG_EXPAND+PNG_SHIFT doing the shift twice.
-  Recognize known sRGB ICC profiles while reading; prefer writing the
-    iCCP profile over writing the sRGB chunk, controlled by the
-    PNG_sRGB_PROFILE_CHECKS option.
-  Revised png_set_text_2() to avoid potential memory corruption (fixes
-    CVE-2011-3048, also known as CVE-2012-3425).
-
-Version 1.6.0beta21 [April 27, 2012]
-  Revised scripts/makefile.darwin: use system zlib; remove quotes around
-    architecture list; add missing ppc architecture; add architecture options
-    to shared library link; don't try to create a shared lib based on missing
-    RELEASE variable.
-  Enable png_set_check_for_invalid_index() for both read and write.
-  Removed #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED in pngpriv.h around
-    declaration of png_handle_unknown().
-  Added -lssp_nonshared in a comment in scripts/makefile.freebsd
-    and changed deprecated NOOBJ and NOPROFILE to NO_OBJ and NO_PROFILE.
-
-Version 1.6.0beta22 [May 23, 2012]
-  Removed need for -Wno-cast-align with clang.  clang correctly warns on
-    alignment increasing pointer casts when -Wcast-align is passed. This
-    fixes the cases that clang warns about either by eliminating the
-    casts from png_bytep to png_uint_16p (pngread.c), or, for pngrutil.c
-    where the cast is previously verified or pngstest.c where it is OK, by
-    introducing new png_aligncast macros to do the cast in a way that clang
-    accepts.
-
-Version 1.6.0beta23 [June 6, 2012]
-  Revised CMakeLists.txt to not attempt to make a symlink under mingw.
-  Made fixes for new optimization warnings from gcc 4.7.0. The compiler
-    performs an optimization which is safe; however it then warns about it.
-    Changing the type of 'palette_number' in pngvalid.c removes the warning.
-  Do not depend upon a GCC feature macro being available for use in generating
-    the linker mapfile symbol prefix.
-  Improved performance of new do_check_palette_indexes() function (only
-    update the value when it actually increases, move test for whether
-    the check is wanted out of the function.
-
-Version 1.6.0beta24 [June 7, 2012]
-  Don't check palette indexes if num_palette is 0 (as it can be in MNG files).
-
-Version 1.6.0beta25 [June 16, 2012]
-  Revised png_set_keep_unknown_chunks() so num_chunks < 0 means ignore all
-    unknown chunks and all known chunks except for IHDR, PLTE, tRNS, IDAT,
-    and IEND.  Previously it only meant ignore all unknown chunks, the
-    same as num_chunks == 0. Revised png_image_skip_unused_chunks() to
-    provide a list of chunks to be processed instead of a list of chunks to
-    ignore.  Revised contrib/gregbook/readpng2.c accordingly.
-
-Version 1.6.0beta26 [July 10, 2012]
-  Removed scripts/makefile.cegcc from the *.zip and *.7z distributions; it
-    depends on configure, which is not included in those archives.
-  Moved scripts/chkfmt to contrib/tools.
-  Changed "a+w" to "u+w" in Makefile.in to fix CVE-2012-3386.
-
-Version 1.6.0beta27 [August 11, 2012]
-  Do not compile PNG_DEPRECATED, PNG_ALLOC and PNG_PRIVATE when __GNUC__ < 3.
-  Do not use __restrict when GNUC is <= 3.1
-  Removed references to png_zalloc() and png_zfree() from the manual.
-  Fixed configurations where floating point is completely disabled.  Because
-    of the changes to support symbol prefixing PNG_INTERNAL_FUNCTION declares
-    floating point APIs during libpng builds even if they are completely
-    disabled. This requires the png floating point types (png_double*) to be
-    declared even though the functions are never actually defined.  This
-    change provides a dummy definition so that the declarations work, yet any
-    implementation will fail to compile because of an incomplete type.
-  Re-eliminated the use of strcpy() in pngtest.c.  An unncessary use of
-    strcpy() was accidentally re-introduced in libpng16; this change replaces
-    it with strncpy().
-  Eliminated use of png_sizeof(); use sizeof() instead.
-  Use a consistent style for (sizeof type) and (sizeof (array))
-  Cleanup of png_set_filler().  This function does very different things on
-    read and write.  In libpng 1.6 the two cases can be distinguished and
-    considerable code cleanup, and extra error checking, is possible.  This
-    makes calls on the write side that have no effect be ignored with a
-    png_app_error(), which can be disabled in the app using
-    png_set_benign_errors(), and removes the spurious use of usr_channels
-    on the read side.
-  Insist on autotools 1.12.1 for git builds because there are security issues
-    with 1.12 and insisting on anything less would allow 1.12 to be used.
-  Removed info_ptr->signature[8] from WRITE-only builds.
-  Add some conditions for compiling png_fixed().  This is a small function
-    but it requires "-lm" on some platforms.
-  Cause pngtest --strict to fail on any warning from libpng (not just errors)
-    and cause it not to fail at the comparison step if libpng lacks support
-    for writing chunks that it reads from the input (currently only implemented
-    for compressed text chunks).
-  Make all three "make check" test programs work without READ or WRITE support.
-    Now "make check" will succeed even if libpng is compiled with -DPNG_NO_READ
-    or -DPNG_NO_WRITE.  The tests performed are reduced, but the basic reading
-    and writing of a PNG file is always tested by one or more of the tests.
-  Consistently use strlen(), memset(), memcpy(), and memcmp() instead of the
-    png_strlen(), png_memset(), png_memcpy(), and png_memcmp() macros.
-  Removed the png_sizeof(), png_strlen(), png_memset(), png_memcpy(), and
-    png_memcmp() macros.
-  Work around gcc 3.x and Microsoft Visual Studio 2010 complaints. Both object
-    to the split initialization of num_chunks.
-
-Version 1.6.0beta28 [August 29, 2012]
-  Unknown handling fixes and clean up. This adds more correct option
-    control of the unknown handling, corrects the pre-existing bug where
-    the per-chunk 'keep' setting is ignored and makes it possible to skip
-    IDAT chunks in the sequential reader (broken in earlier 1.6 versions).
-    There is a new test program, test-unknown.c, which is a work in progress
-    (not currently part of the test suite).  Comments in the header files now
-    explain how the unknown handling works.
-  Allow fine grain control of unknown chunk APIs. This change allows
-    png_set_keep_unknown_chunks() to be turned off if not required and causes
-    both read and write to behave appropriately (on read this is only possible
-    if the user callback is used to handle unknown chunks).  The change
-    also removes the support for storing unknown chunks in the info_struct
-    if the only unknown handling enabled is via the callback, allowing libpng
-    to be configured with callback reading and none of the unnecessary code.
-  Corrected fix for unknown handling in pngtest. This reinstates the
-    libpng handling of unknown chunks other than vpAg and sTER (including
-    unsafe-to-copy chunks which were dropped before) and eliminates the
-    repositioning of vpAg and sTER in pngtest.png by changing pngtest.png
-    (so the chunks are where libpng would put them).
-  Added "tunknown" test and corrected a logic error in png_handle_unknown()
-    when SAVE support is absent.  Moved the shell test scripts for
-    contrib/libtests from the libpng top directory to contrib/libtests.
-    png_handle_unknown() must always read or skip the chunk, if
-    SAVE_UNKNOWN_CHUNKS is turned off *and* the application does not set
-    a user callback an unknown chunk will not be read, leading to a read
-    error, which was revealed by the "tunknown" test.
-  Cleaned up and corrected ICC profile handling.
-    contrib/libtests/makepng: corrected 'rgb' and 'gray' cases.  profile_error
-    messages could be truncated; made a correct buffer size calculation and
-    adjusted pngerror.c appropriately. png_icc_check_* checking improved;
-    changed the functions to receive the correct color type of the PNG on read
-    or write and check that it matches the color space of the profile (despite
-    what the comments said before, there is danger in assuming the app will
-    cope correctly with an RGB profile on a grayscale image and, since it
-    violates the PNG spec, allowing it is certain to produce inconsistent
-    app behavior and might even cause app crashes.) Check that profiles
-    contain the tags needed to process the PNG (tags all required by the ICC
-    spec). Removed unused PNG_STATIC from pngpriv.h.
-
-Version 1.6.0beta29 [September 4, 2012]
-  Fixed the simplified API example programs to add the *colormap parameter
-    to several of he API and improved the error message if the version field
-    is not set.
-  Added contrib/examples/* to the *.zip and *.7z distributions.
-  Updated simplified API synopses and description of the png_image structure
-    in the manual.
-  Made makepng and pngtest produce identical PNGs, add "--relaxed" option
-    to pngtest. The "--relaxed" option turns off the benign errors that are
-    enabled by default in pre-RC builds. makepng can now write ICC profiles
-    where the length has not been extended to a multiple of 4, and pngtest
-    now intercepts all libpng errors, allowing the previously-introduced
-    "--strict test" on no warnings to actually work.
-  Improved ICC profile handling including cHRM chunk generation and fixed
-    Cygwin+MSVC build errors. The ICC profile handling now includes more
-    checking.  Several errors that caused rejection of the profile are now
-    handled with a warning in such a way that the invalid profiles will be
-    read by default in release (but not pre-RC) builds but will not be
-    written by default.  The easy part of handling the cHRM chunk is written,
-    where the ICC profile contains the required data.  The more difficult
-    part plus guessing a gAMA value requires code to pass selected RGB values
-    through the profile.
-
-Version 1.6.0beta30 [October 24, 2012]
-  Changed ICC profile matrix/vector types to not depend on array type rules.
-    By the ANSI-C standard the new types should be identical to the previous
-    versions, and all known versions of gcc tested with the previous versions
-    except for GCC-4.2.1 work with this version.  The change makes the ANSI-C
-    rule that const applied to an array of elements applies instead to the
-    elements in the array moot by explicitly applying const to the base
-    elements of the png_icc_matrix and png_icc_vector types. The accidental
-    (harmless) 'const' previously applied to the parameters of two of the
-    functions have also been removed.
-  Added a work around for GCC 4.2 optimization bug.
-  Marked the broken (bad white point) original HP sRGB profiles correctly and
-    correct comments.
-  Added -DZ_SOLO to contrib/pngminim/*/makefile to work with zlib-1.2.7
-  Use /MDd for vstudio debug builds. Also added pngunkown to the vstudio
-    builds, fixed build errors and corrected a minor exit code error in
-    pngvalid if the 'touch' file name is invalid.
-  Add updated WARNING file to projects/vstudio from libpng 1.5/vstudio
-  Fixed build when using #define PNG_NO_READ_GAMMA in png_do_compose() in
-    pngrtran.c (Domani Hannes).
-
-Version 1.6.0beta31 [November 1, 2012]
-  Undid the erroneous change to vstudio/pngvalid build in libpng-1.6.0beta30.
-  Made pngvalid so that it will build outside the libpng source tree.
-  Made builds -DPNG_NO_READ_GAMMA compile (the unit tests still fail).
-  Made PNG_NO_READ_GAMMA switch off interfaces that depend on READ_GAMMA.
-    Prior to 1.6.0 switching off READ_GAMMA did unpredictable things to the
-    interfaces that use it (specifically, png_do_background in 1.4 would
-    simply display composite for grayscale images but do composition
-    with the incorrect arithmetic for color ones). In 1.6 the semantic
-    of -DPNG_NO_READ_GAMMA is changed to simply disable any interface that
-    depends on it; this obliges people who set it to consider whether they
-    really want it off if they happen to use any of the interfaces in
-    question (typically most users who disable it won't).
-  Fixed GUIDs in projects/vstudio. Some were duplicated or missing,
-    resulting in VS2010 having to update the files.
-  Removed non-working ICC profile support code that was mostly added to
-    libpng-1.6.0beta29 and beta30. There was too much code for too little
-    gain; implementing full ICC color correction may be desireable but is left
-    up to applications.
-
-Version 1.6.0beta32 [November 25, 2012]
-  Fixed an intermittent SEGV in pngstest due to an uninitialized array element.
-  Added the ability for contrib/libtests/makepng.c to make a PNG with just one
-    color. This is useful for debugging pngstest color inaccuracy reports.
-  Fixed error checking in the simplified write API (Olaf van der Spek)
-  Made png_user_version_check() ok to use with libpng version 1.10.x and later.
-
-Version 1.6.0beta33 [December 15, 2012]
-  Fixed typo in png.c (PNG_SET_CHUNK_MALLOC_MAX should be PNG_CHUNK_MALLOC_MAX)
-    that causes the MALLOC_MAX limit not to work (John Bowler)
-  Change png_warning() to png_app_error() in pngwrite.c and comment the
-    fall-through condition.
-  Change png_warning() to png_app_warning() in png_write_tRNS().
-  Rearranged the ARM-NEON optimizations: Isolated the machine specific code
-    to the hardware subdirectory and added comments to pngrutil.c so that
-    implementors of other optimizations know what to do.
-  Fixed cases of unquoted DESTDIR in Makefile.am
-  Rebuilt Makefile.in, etc., with autoconf-2.69 and automake-1.12.5.
-
-Version 1.6.0beta34 [December 19, 2012]
-  Cleaned up whitespace in the synopsis portion of the manpage "libpng.3"
-  Disassembled the version number in scripts/options.awk (necessary for
-    building on SunOs).
-
-Version 1.6.0beta35 [December 23, 2012]
-  Made default Zlib compression settings be configurable. This adds #defines to
-    pnglibconf.h to control the defaults.
-  Fixed Windows build issues, enabled ARM compilation. Various warnings issued
-    by earlier versions of GCC fixed for Cygwin and Min/GW (which both use old
-    GCCs.) ARM support is enabled by default in zlib.props (unsupported by
-    Microsoft) and ARM compilation is made possible by deleting the check for
-    x86. The test programs cannot be run because they are not signed.
-
-Version 1.6.0beta36 [January 2, 2013]
-  Discontinued distributing libpng-1.x.x.tar.bz2.
-  Discontinued distributing libpng-1.7.0-1.6.0-diff.txt and similar.
-  Rebuilt configure with autoconf-2.69 (inadvertently not done in beta33)
-  Fixed 'make distcheck' on SUN OS - libpng.so was not being removed
-
-Version 1.6.0beta37 [January 10, 2013]
-  Fixed conceivable but difficult to repro overflow. Also added two test
-    programs to generate and test a PNG which should have the problem.
-
-Version 1.6.0beta39 [January 19, 2013]
-  Again corrected attempt at overflow detection in png_set_unknown_chunks()
-  (CVE-2013-7353).  Added overflow detection in png_set_sPLT() and
-  png_set_text_2() (CVE-2013-7354).
-
-Version 1.6.0beta40 [January 20, 2013]
-  Use consistent handling of overflows in text, sPLT and unknown png_set_* APIs
-
-Version 1.6.0rc01 [January 26, 2013]
-  No changes.
-
-Version 1.6.0rc02 [February 4, 2013]
-  Added png_get_palette_max() function.
-
-Version 1.6.0rc03 [February 5, 2013]
-  Fixed the png_get_palette_max API.
-
-Version 1.6.0rc04 [February 7, 2013]
-  Turn serial tests back on (recently turned off by autotools upgrade).
-
-Version 1.6.0rc05 [February 8, 2013]
-  Update manual about png_get_palette_max().
-
-Version 1.6.0rc06 [February 9, 2013]
-  Fixed missing dependency in --prefix builds The intermediate
-    internal 'prefix.h' file can only be generated correctly after
-    pnglibconf.h, however the dependency was not in Makefile.am.  The
-    symptoms are unpredictable depending on the order make chooses to
-    build pngprefix.h and pnglibconf.h, often the error goes unnoticed
-    because there is a system pnglibconf.h to use instead.
-
-Version 1.6.0rc07 [February 10, 2013]
-  Enclosed the new png_get_palette_max in #ifdef PNG_GET_PALETTE_MAX_SUPPORTED
-    block, and revised pnglibconf.h and pnglibconf.h.prebuilt accordingly.
-
-Version 1.6.0rc08 [February 10, 2013]
-  Fix typo in png.h #ifdef
-
-Version 1.6.0 [February 14, 2013]
-  No changes.
-
-Version 1.6.1beta01 [February 16, 2013]
-  Made symbol prefixing work with the ARM neon optimizations. Also allow
-    pngpriv.h to be included for preprocessor definitions only, so it can
-    be used in non-C/C++ files. Back ported from libpng 1.7.
-  Made sRGB check numbers consistent.
-  Ported libpng 1.5 options.awk/dfn file handling to 1.6, fixed one bug.
-  Removed cc -E workround, corrected png_get_palette_max API Tested on
-    SUN OS cc 5.9, which demonstrates the tokenization problem previously
-    avoided by using /lib/cpp.  Since all .dfn output is now protected in
-    double quotes unless it is to be macro substituted the fix should
-    work everywhere.
-  Enabled parallel tests - back ported from libpng-1.7.
-  scripts/pnglibconf.dfa formatting improvements back ported from libpng17.
-  Fixed a race condition in the creation of the build 'scripts' directory
-    while building with a parallel make.
-  Use approved/supported Android method to check for NEON, use Linux/POSIX
-    1003.1 API to check /proc/self/auxv avoiding buffer allocation and other
-    library calls (ported from libpng15).
-
-Version 1.6.1beta02 [February 19, 2013]
-  Use parentheses more consistently in "#if defined(MACRO)" tests.
-  Folded long lines.
-  Reenabled code to allow zero length PLTE chunks for MNG.
-
-Version 1.6.1beta03 [February 22, 2013]
-  Fixed ALIGNED_MEMORY support.
-  Added a new configure option:
-    --enable-arm-neon=always will stop the run-time checks. New checks
-    within arm/arm_init.c will cause the code not to be compiled unless
-    __ARM_NEON__ is set. This should make it fail safe (if someone asks
-    for it on then the build will fail if it can't be done.)
-  Updated the INSTALL document.
-
-Version 1.6.1beta04 [February 27, 2013]
-  Revised INSTALL to recommend using CPPFLAGS instead of INCLUDES.
-  Revised scripts/makefile.freebsd to respect ZLIBLIB and ZLIBINC.
-  Revised scripts/dfn.awk to work with the buggy MSYS awk that has trouble
-    with CRLF line endings.
-
-Version 1.6.1beta05 [March 1, 2013]
-  Avoid a possible memory leak in contrib/gregbook/readpng.c
-
-Version 1.6.1beta06 [March 4, 2013]
-  Better documentation of unknown handling API interactions.
-  Corrected Android builds and corrected libpng.vers with symbol
-    prefixing.  It also makes those tests compile and link on Android.
-  Added an API png_set_option() to set optimization options externally,
-    providing an alternative and general solution for the non-portable
-    run-time tests used by the ARM Neon code, using the PNG_ARM_NEON option.
-  The order of settings vs options in pnglibconf.h is reversed to allow
-    settings to depend on options and options can now set (or override) the
-    defaults for settings.
-
-Version 1.6.1beta07 [March 7, 2013]
-  Corrected simplified API default gamma for color-mapped output, added
-    a flag to change default. In 1.6.0 when the simplified API was used
-    to produce color-mapped output from an input image with no gamma
-    information the gamma assumed for the input could be different from
-    that assumed for non-color-mapped output.  In particular 16-bit depth
-    input files were assumed to be sRGB encoded, whereas in the 'direct'
-    case they were assumed to have linear data.  This was an error.  The
-    fix makes the simplified API treat all input files the same way and
-    adds a new flag to the png_image::flags member to allow the
-    application/user to specify that 16-bit files contain sRGB data
-    rather than the default linear.
-  Fixed bugs in the pngpixel and makepng test programs.
-
-Version 1.6.1beta08 [March 7, 2013]
-  Fixed CMakelists.txt to allow building a single variant of the library
-    (Claudio Bley):
-  Introduced a PNG_LIB_TARGETS variable that lists all activated library
-    targets.  It is an error if this variable ends up empty, ie. you have
-    to build at least one library variant.
-  Made the *_COPY targets only depend on library targets actually being build.
-  Use PNG_LIB_TARGETS to unify a code path.
-  Changed the CREATE_SYMLINK macro to expect the full path to a file as the
-    first argument. When symlinking the filename component of that path is
-    determined and used as the link target.
-  Use copy_if_different in the CREATE_SYMLINK macro.
-
-Version 1.6.1beta09 [March 13, 2013]
-  Eliminated two warnings from the Intel C compiler. The warnings are
-    technically valid, although a reasonable treatment of division would
-    show it to be incorrect.
-
-Version 1.6.1rc01 [March 21, 2013]
-  No changes.
-
-Version 1.6.1 [March 28, 2013]
-  No changes.
-
-Version 1.6.2beta01 [April 14, 2013]
-  Updated documentation of 1.5.x to 1.6.x changes in iCCP chunk handling.
-  Fixed incorrect warning of excess deflate data. End condition - the
-    warning would be produced if the end of the deflate stream wasn't read
-    in the last row.  The warning is harmless.
-  Corrected the test on user transform changes on read. It was in the
-    png_set of the transform function, but that doesn't matter unless the
-    transform function changes the rowbuf size, and that is only valid if
-    transform_info is called.
-  Corrected a misplaced closing bracket in contrib/libtests/pngvalid.c
-    (Flavio Medeiros).
-  Corrected length written to uncompressed iTXt chunks (Samuli Suominen).
-    Bug was introduced in libpng-1.6.0.
-
-Version 1.6.2rc01 [April 18, 2013]
-  Added contrib/tools/fixitxt.c, to repair the erroneous iTXt chunk length
-    written by libpng-1.6.0 and 1.6.1.
-  Disallow storing sRGB information when the sRGB is not supported.
-
-Version 1.6.2rc02 [April 18, 2013]
-  Merge pngtest.c with libpng-1.7.0
-
-Version 1.6.2rc03 [April 22, 2013]
-  Trivial spelling cleanup.
-
-Version 1.6.2rc04 and 1.6.2rc05 [omitted]
-
-Version 1.6.2rc06 [April 24, 2013]
-  Reverted to version 1.6.2rc03.  Recent changes to arm/neon support
-    have been ported to libpng-1.7.0beta09 and will reappear in version
-    1.6.3beta01.
-
-Version 1.6.2 [April 25, 2013]
-  No changes.
-
-Version 1.6.3beta01 [April 25, 2013]
-  Revised stack marking in arm/filter_neon.S and configure.ac.
-  Ensure that NEON filter stuff is completely disabled when switched 'off'.
-    Previously the ARM NEON specific files were still built if the option
-    was switched 'off' as opposed to being explicitly disabled.
-
-Version 1.6.3beta02 [April 26, 2013]
-  Test for 'arm*' not just 'arm' in the host_cpu configure variable.
-  Rebuilt the configure scripts.
-
-Version 1.6.3beta03 [April 30, 2013]
-  Expanded manual paragraph about writing private chunks, particularly
-    the need to call png_set_keep_unknown_chunks() when writing them.
-  Avoid dereferencing NULL pointer possibly returned from
-    png_create_write_struct() (Andrew Church).
-
-Version 1.6.3beta05 [May 9, 2013]
-  Calculate our own zlib windowBits when decoding rather than trusting the
-    CMF bytes in the PNG datastream.
-  Added an option to force maximum window size for inflating, which was
-    the behavior of libpng15 and earlier, via a new PNG_MAXIMUM_INFLATE_WINDOW
-    option for png_set_options().
-  Added png-fix-itxt and png-fix-too-far-back to the built programs and
-    removed warnings from the source code and timepng that are revealed as
-    a result.
-  Detect wrong libpng versions linked to png-fix-too-far-back, which currently
-    only works with libpng versions that can be made to reliably fail when
-    the deflate data contains an out-of-window reference.  This means only
-    1.6 and later.
-  Fixed gnu issues: g++ needs a static_cast, gcc 4.4.7 has a broken warning
-    message which it is easier to work round than ignore.
-  Updated contrib/pngminus/pnm2png.c (Paul Stewart):
-    Check for EOF
-    Ignore "#" delimited comments in input file to pnm2png.c.
-    Fixed whitespace handling
-    Added a call to png_set_packing()
-    Initialize dimension values so if sscanf fails at least we have known
-      invalid values.
-  Attempt to detect configuration issues with png-fix-too-far-back, which
-    requires both the correct libpng and the correct zlib to function
-    correctly.
-  Check ZLIB_VERNUM for mismatches, enclose #error in quotes
-  Added information in the documentation about problems with and fixes for
-    the bad CRC and bad iTXt chunk situations.
-
-Version 1.6.3beta06 [May 12, 2013]
-  Allow contrib/pngminus/pnm2png.c to compile without WRITE_INVERT and
-    WRITE_PACK supported (writes error message that it can't read P1 or
-    P4 PBM files).
-  Improved png-fix-too-far-back usage message, added --suffix option.
-  Revised contrib/pngminim/*/makefile to generate pnglibconf.h with the
-    right zlib header files.
-  Separated CPPFLAGS and CFLAGS in contrib/pngminim/*/makefile
-
-Version 1.6.3beta07 [June 8, 2013]
-  Removed a redundant test in png_set_IHDR().
-  Added set(CMAKE_CONFIGURATION_TYPES ...) to CMakeLists.txt (Andrew Hundt)
-  Deleted set(CMAKE_BUILD_TYPE) block from CMakeLists.txt
-  Enclose the prototypes for the simplified write API in
-    #ifdef PNG_STDIO_SUPPORTED/#endif
-  Make ARM NEON support work at compile time (not just configure time).
-    This moves the test on __ARM_NEON__ into pngconf.h to avoid issues when
-    using a compiler that compiles for multiple architectures at one time.
-  Removed PNG_FILTER_OPTIMIZATIONS and PNG_ARM_NEON_SUPPORTED from
-    pnglibconf.h, allowing more of the decisions to be made internally
-    (pngpriv.h) during the compile.  Without this, symbol prefixing is broken
-    under certain circumstances on ARM platforms.  Now only the API parts of
-    the optimizations ('check' vs 'api') are exposed in the public header files
-    except that the new setting PNG_ARM_NEON_OPT documents how libpng makes the
-    decision about whether or not to use the optimizations.
-  Protect symbol prefixing against CC/CPPFLAGS/CFLAGS useage.
-    Previous iOS/Xcode fixes for the ARM NEON optimizations moved the test
-    on __ARM_NEON__ from configure time to compile time.  This breaks symbol
-    prefixing because the definition of the special png_init_filter_functions
-    call was hidden at configure time if the relevant compiler arguments are
-    passed in CFLAGS as opposed to CC.  This change attempts to avoid all
-    the confusion that would result by declaring the init function even when
-    it is not used, so that it will always get prefixed.
-
-Version 1.6.3beta08 [June 18, 2013]
-  Revised libpng.3 so that "doclifter" can process it.
-
-Version 1.6.3beta09 [June 27, 2013]
-  Revised example.c to illustrate use of PNG_DEFAULT_sRGB and PNG_GAMMA_MAC_18
-    as parameters for png_set_gamma().  These have been available since
-    libpng-1.5.4.
-  Renamed contrib/tools/png-fix-too-far-back.c to pngfix.c and revised it
-    to check all compressed chunks known to libpng.
-
-Version 1.6.3beta10 [July 5, 2013]
-  Updated documentation to show default behavior of benign errors correctly.
-  Only compile ARM code when PNG_READ_SUPPORTED is defined.
-  Fixed undefined behavior in contrib/tools/pngfix.c and added new strip
-    option. pngfix relied on undefined behavior and even a simple change from
-    gcc to g++ caused it to fail.  The new strip option 'unsafe' has been
-    implemented and is the default if --max is given.  Option names have
-    been clarified, with --strip=transform now stripping the bKGD chunk,
-    which was stripped previously with --strip=unused.
-  Added all documented chunk types to pngpriv.h
-  Unified pngfix.c source with libpng17.
-
-Version 1.6.3rc01 [July 11, 2013]
-  No changes.
-
-Version 1.6.3 [July 18, 2013]
-  Revised manual about changes in iTXt chunk handling made in libpng-1.6.0.
-  Added "/* SAFE */" comments in pngrutil.c and pngrtran.c where warnings
-    may be erroneously issued by code-checking applications.
-
-Version 1.6.4beta01 [August 21, 2013]
-  Added information about png_set_options() to the manual.
-  Delay calling png_init_filter_functions() until a row with nonzero filter
-    is found.
-
-Version 1.6.4beta02 [August 30, 2013]
-  Fixed inconsistent conditional compilation of png_chunk_unknown_handling()
-    prototype, definition, and usage.  Made it depend on
-    PNG_HANDLE_AS_UNKNOWN_SUPPORTED everywhere.
-
-Version 1.6.4rc01 [September 5, 2013]
-  No changes.
-
-Version 1.6.4 [September 12, 2013]
-  No changes.
-
-Version 1.6.5 [September 14, 2013]
-  Removed two stray lines of code from arm/arm_init.c.
-
-Version 1.6.6 [September 16, 2013]
-  Removed two stray lines of code from arm/arm_init.c, again.
-
-Version 1.6.7beta01 [September 30, 2013]
-  Revised unknown chunk code to correct several bugs in the NO_SAVE_/NO_WRITE
-    combination
-  Allow HANDLE_AS_UNKNOWN to work when other options are configured off. Also
-    fixed the pngminim makefiles to work when $(MAKEFLAGS) contains stuff
-    which terminates the make options (as by default in recent versions of
-    Gentoo).
-  Avoid up-cast warnings in pngvalid.c. On ARM the alignment requirements of
-    png_modifier are greater than that of png_store and as a consequence
-    compilation of pngvalid.c results in a warning about increased alignment
-    requirements because of the bare cast to (png_modifier*). The code is safe,
-    because the pointer is known to point to a stack allocated png_modifier,
-    but this change avoids the warning.
-  Fixed default behavior of ARM_NEON_API. If the ARM NEON API option was
-    compiled without the CHECK option it defaulted to on, not off.
-  Check user callback behavior in pngunknown.c. Previous versions compiled
-    if SAVE_UNKNOWN was not available but did nothing since the callback
-    was never implemented.
-  Merged pngunknown.c with 1.7 version and back ported 1.7 improvements/fixes
-
-Version 1.6.7beta02 [October 12, 2013]
-  Made changes for compatibility with automake 1.14:
-    1) Added the 'compile' program to the list of programs that must be cleaned
-       in autogen.sh
-    2) Added 'subdir-objects' which causes .c files in sub-directories to be
-       compiled such that the corresponding .o files are also in the
-       sub-directory.  This is because automake 1.14 warns that the
-       current behavior of compiling to the top level directory may be removed
-       in the future.
-    3) Updated dependencies on pnglibconf.h to match the new .o locations and
-       added all the files in contrib/libtests and contrib/tools that depend
-       on pnglibconf.h
-    4) Added 'BUILD_SOURCES = pnglibconf.h'; this is the automake recommended
-       way of handling the dependencies of sources that are machine generated;
-       unfortunately it only works if the user does 'make all' or 'make check',
-       so the dependencies (3) are still required.
-  Cleaned up (char*) casts of zlib messages. The latest version of the Intel C
-    compiler complains about casting a string literal as (char*), so copied the
-    treatment of z_const from the library code into pngfix.c
-  Simplified error message code in pngunknown. The simplification has the
-    useful side effect of avoiding a bogus warning generated by the latest
-    version of the Intel C compiler (it objects to
-    condition ? string-literal : string-literal).
-  Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
-    removing the 1.14 'compile' script but never checking for it.
-
-Version 1.6.7beta03 [October 19, 2013]
-  Added ARMv8 support (James Yu <james.yu at linaro.org>).  Added file
-    arm/filter_neon_intrinsics.c; enable with -mfpu=neon.
-  Revised pngvalid to generate size images with as many filters as it can
-    manage, limited by the number of rows.
-  Cleaned up ARM NEON compilation handling. The tests are now in pngpriv.h
-    and detect the broken GCC compilers.
-
-Version 1.6.7beta04 [October 26, 2013]
-  Allow clang derived from older GCC versions to use ARM intrinsics. This
-    causes all clang builds that use -mfpu=neon to use the intrinsics code,
-    not the assembler code.  This has only been tested on iOS 7. It may be
-    necessary to exclude some earlier clang versions but this seems unlikely.
-  Changed NEON implementation selection mechanism. This allows assembler
-    or intrinsics to be turned on at compile time during the build by defining
-    PNG_ARM_NEON_IMPLEMENTATION to the correct value (2 or 1).  This macro
-    is undefined by default and the build type is selected in pngpriv.h.
-
-Version 1.6.7rc01 [November 2, 2013]
-  No changes.
-
-Version 1.6.7rc02 [November 7, 2013]
-  Fixed #include in filter_neon_intrinsics.c and ctype macros. The ctype char
-    checking macros take an unsigned char argument, not a signed char.
-
-Version 1.6.7 [November 14, 2013]
-  No changes.
-
-Version 1.6.8beta01 [November 24, 2013]
-  Moved prototype for png_handle_unknown() in pngpriv.h outside of
-    the #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED/#endif block.
-  Added "-Wall" to CFLAGS in contrib/pngminim/*/makefile
-  Conditionally compile some unused functions reported by -Wall in
-    pngminim.
-  Fixed 'minimal' builds. Various obviously useful minimal configurations
-    don't build because of missing contrib/libtests test programs and
-    overly complex dependencies in scripts/pnglibconf.dfa. This change
-    adds contrib/conftest/*.dfa files that can be used in automatic build
-    scripts to ensure that these configurations continue to build.
-  Enabled WRITE_INVERT and WRITE_PACK in contrib/pngminim/encoder.
-  Fixed pngvalid 'fail' function declaration on the Intel C Compiler.
-    This reverts to the previous 'static' implementation and works round
-    the 'unused static function' warning by using PNG_UNUSED().
-
-Version 1.6.8beta02 [November 30, 2013]
-  Removed or marked PNG_UNUSED some harmless "dead assignments" reported
-    by clang scan-build.
-  Changed tabs to 3 spaces in png_debug macros and changed '"%s"m'
-    to '"%s" m' to improve portability among compilers.
-  Changed png_free_default() to free() in pngtest.c
-
-Version 1.6.8rc01 [December 12, 2013]
-  Tidied up pngfix inits and fixed pngtest no-write builds.
-
-Version 1.6.8rc02 [December 14, 2013]
-  Handle zero-length PLTE chunk or NULL palette with png_error()
-    instead of png_chunk_report(), which by default issues a warning
-    rather than an error, leading to later reading from a NULL pointer
-    (png_ptr->palette) in png_do_expand_palette(). This is CVE-2013-6954
-    and VU#650142.  Libpng-1.6.1 through 1.6.7 are vulnerable.
-    Libpng-1.6.0 and earlier do not have this bug.
-
-Version 1.6.8 [December 19, 2013]
-  No changes.
-
-Version 1.6.9beta01 [December 26, 2013]
-  Bookkeeping: Moved functions around (no changes). Moved transform
-    function definitions before the place where they are called so that
-    they can be made static. Move the intrapixel functions and the
-    grayscale palette builder out of the png?tran.c files. The latter
-    isn't a transform function and is no longer used internally, and the
-    former MNG specific functions are better placed in pngread/pngwrite.c
-  Made transform implementation functions static. This makes the internal
-    functions called by png_do_{read|write}_transformations static. On an
-    x86-64 DLL build (Gentoo Linux) this reduces the size of the text
-    segment of the DLL by 1208 bytes, about 0.6%. It also simplifies
-    maintenance by removing the declarations from pngpriv.h and allowing
-    easier changes to the internal interfaces.
-  Rebuilt configure scripts with automake-1.14.1 and autoconf-2.69
-    in the tar distributions.
-
-Version 1.6.9beta02 [January 1, 2014]
-  Added checks for libpng 1.5 to pngvalid.c.  This supports the use of
-    this version of pngvalid in libpng 1.5
-  Merged with pngvalid.c from libpng-1.7 changes to create a single
-    pngvalid.c
-  Removed #error macro from contrib/tools/pngfix.c (Thomas Klausner).
-  Merged pngrio.c, pngtrans.c, pngwio.c, and pngerror.c with libpng-1.7.0
-  Merged libpng-1.7.0 changes to make no-interlace configurations work
-    with test programs.
-  Revised pngvalid.c to support libpng 1.5, which does not support the
-    PNG_MAXIMUM_INFLATE_WINDOW option, so #define it out when appropriate in
-    pngvalid.c
-  Allow unversioned links created on install to be disabled in configure.
-    In configure builds 'make install' changes/adds links like png.h
-    and libpng.a to point to the newly installed, versioned, files (e.g.
-    libpng17/png.h and libpng17.a). Three new configure options and some
-    rearrangement of Makefile.am allow creation of these links to be disabled.
-
-Version 1.6.9beta03 [January 10, 2014]
-  Removed potentially misleading warning from png_check_IHDR().
-
-Version 1.6.9beta04 [January 20, 2014]
-  Updated scripts/makefile.* to use CPPFLAGS (Cosmin).
-  Added clang attribute support (Cosmin).
-
-Version 1.6.9rc01 [January 28, 2014]
-  No changes.
-
-Version 1.6.9rc02 [January 30, 2014]
-  Quiet an uninitialized memory warning from VC2013 in png_get_png().
-
-Version 1.6.9 [February 6, 2014]
-
-Version 1.6.10beta01 [February 9, 2014]
-  Backported changes from libpng-1.7.0beta30 and beta31:
-  Fixed a large number of instances where PNGCBAPI was omitted from
-    function definitions.
-  Added pngimage test program for png_read_png() and png_write_png()
-    with two new test scripts.
-  Removed dependence on !PNG_READ_EXPAND_SUPPORTED for calling
-    png_set_packing() in png_read_png().
-  Fixed combination of ~alpha with shift. On read invert alpha, processing
-    occurred after shift processing, which causes the final values to be
-    outside the range that should be produced by the shift. Reversing the
-    order on read makes the two transforms work together correctly and mirrors
-    the order used on write.
-  Do not read invalid sBIT chunks. Previously libpng only checked sBIT
-    values on write, so a malicious PNG writer could therefore cause
-    the read code to return an invalid sBIT chunk, which might lead to
-    application errors or crashes.  Such chunks are now skipped (with
-    chunk_benign_error).
-  Make png_read_png() and png_write_png() prototypes in png.h depend
-    upon PNG_READ_SUPPORTED and PNG_WRITE_SUPPORTED.
-  Support builds with unsupported PNG_TRANSFORM_* values.  All of the
-    PNG_TRANSFORM_* values are always defined in png.h and, because they
-    are used for both read and write in some cases, it is not reliable
-    to #if out ones that are totally unsupported. This change adds error
-    detection in png_read_image() and png_write_image() to do a
-    png_app_error() if the app requests something that cannot be done
-    and it adds corresponding code to pngimage.c to handle such options
-    by not attempting to test them.
-
-Version 1.6.10beta02 [February 23, 2014]
-  Moved redefines of png_error(), png_warning(), png_chunk_error(),
-    and png_chunk_warning() from pngpriv.h to png.h to make them visible
-    to libpng-calling applications.
-  Moved OS dependent code from arm/arm_init.c, to allow the included
-    implementation of the ARM NEON discovery function to be set at
-    build-time and provide sample implementations from the current code in the
-    contrib/arm-neon subdirectory. The __linux__ code has also been changed to
-    compile and link on Android by using /proc/cpuinfo, and the old linux code
-    is in contrib/arm-neon/linux-auxv.c.  The new code avoids POSIX and Linux
-    dependencies apart from opening /proc/cpuinfo and is C90 compliant.
-  Check for info_ptr == NULL early in png_read_end() so we don't need to
-    run all the png_handle_*() and depend on them to return if info_ptr == NULL.
-    This improves the performance of png_read_end(png_ptr, NULL) and makes
-    it more robust against future programming errors.
-  Check for __has_extension before using it in pngconf.h, to
-    support older Clang versions (Jeremy Sequoia).
-  Treat CRC error handling with png_set_crc_action(), instead of with
-    png_set_benign_errors(), which has been the case since libpng-1.6.0beta18.
-  Use a user warning handler in contrib/gregbook/readpng2.c instead of default,
-    so warnings will be put on stderr even if libpng has CONSOLE_IO disabled.
-  Added png_ptr->process_mode = PNG_READ_IDAT_MODE in png_push_read_chunk
-    after recognizing the IDAT chunk, which avoids an infinite loop while
-    reading a datastream whose first IDAT chunk is of zero-length.
-    This fixes CERT VU#684412 and CVE-2014-0333.
-  Don't recognize known sRGB profiles as sRGB if they have been hacked,
-    but don't reject them and don't issue a copyright violation warning.
-
-Version 1.6.10beta03 [February 25, 2014]
-  Moved some documentation from png.h to libpng.3 and libpng-manual.txt
-  Minor editing of contrib/arm-neon/README and contrib/examples/*.c
-
-Version 1.6.10rc01 [February 27, 2014]
-  Fixed typos in the manual and in scripts/pnglibconf.dfa (CFLAGS -> CPPFLAGS
-    and PNG_USR_CONFIG -> PNG_USER_CONFIG).
-
-Version 1.6.10rc02 [February 28, 2014]
-  Removed unreachable return statement after png_chunk_error()
-    in pngrutil.c
-
-Version 1.6.10rc03 [March 4, 2014]
-  Un-deprecated png_data_freer().
-
-Version 1.6.10 [March 6, 2014]
-  No changes.
-
-Version 1.6.11beta01 [March 17, 2014]
-  Use "if (value != 0)" instead of "if (value)" consistently.
-  Changed ZlibSrcDir from 1.2.5 to 1.2.8 in projects/vstudio.
-  Moved configuration information from the manual to the INSTALL file.
-
-Version 1.6.11beta02 [April 6, 2014]
-  Removed #if/#else/#endif from inside two pow() calls in pngvalid.c because
-    they were handled improperly by Portland Group's PGI-14.1 - PGI-14.3
-    when using its "__builtin_pow()" function.
-  Silence 'unused parameter' build warnings (Cosmin Truta).
-  $(CP) is now used alongside $(RM_F).  Also, use 'copy' instead of 'cp'
-    where applicable, and applied other minor makefile changes (Cosmin).
-  Don't warn about invalid dimensions exceeding user limits (Cosmin).
-  Allow an easy replacement of the default pre-built configuration
-    header with a custom header, via the make PNGLIBCONF_H_PREBUILT
-    macro (Cosmin).
-
-Version 1.6.11beta03 [April 6, 2014]
-  Fixed a typo in pngrutil.c, introduced in libpng-1.5.6, that interferes
-    with "blocky" expansion of sub-8-bit interlaced PNG files (Eric Huss).
-  Optionally use  __builtin_bswap16() in png_do_swap().
-
-Version 1.6.11beta04 [April 19, 2014]
-  Made progressive reading of interlaced images consistent with the
-    behavior of the sequential reader and consistent with the manual, by
-    moving some code out of the PNG_READ_INTERLACING_SUPPORTED blocks. The
-    row_callback now receives the proper pass number and unexpanded rows, when
-    png_combine_row() isn't built or used, and png_set_interlace_handling()
-    is not called.
-  Allow PNG_sRGB_PROFILE_CHECKING = (-1) to mean no sRGB profile checking.
-
-Version 1.6.11beta05 [April 26, 2014]
-  Do not reject ICC V2 profiles that lack padding (Kai-Uwe Behrmann).
-  Relocated closing bracket of the sRGB profile test loop to avoid getting
-    "Not recognizing known sRGB profile that has been edited" warning for
-    ICC V2 profiles that lack the MD5 signature in the profile header.
-
-Version 1.6.11beta06 [May 19, 2014]
-  Added PNG_SKIP_sRGB_CHECK_PROFILE choice for png_set_option().
-
-Version 1.6.11rc01 [May 27, 2014]
-  No changes.
-
-Version 1.6.11rc02 [June 3, 2014]
-  Test ZLIB_VERNUM instead of PNG_ZLIB_VERNUM in contrib/tools/pngfix.c
-
-Version 1.6.11 [June 5, 2014]
-  No changes.
-
-Version 1.6.12rc01 [June 6, 2014]
-  Relocated new code from 1.6.11beta06 in png.c to a point after the
-    declarations (Max Stepin).
-
-Version 1.6.12rc02 [June 7, 2014]
-  Changed file permissions of contrib/tools/intgamma.sh,
-    test-driver, and compile from 0644 to 0755 (Cosmin).
-
-Version 1.6.12rc03 [June 8, 2014]
-  Ensure "__has_attribute()" macro exists before trying to use it with
-    old clang compilers (MacPorts Ticket #43939).
-
-Version 1.6.12 [June 12, 2014]
-  No changes.
-
-Version 1.6.13beta01 [July 4, 2014]
-  Quieted -Wsign-compare and -Wclobber compiler warnings in
-    contrib/pngminus/*.c
-  Added "(void) png_ptr;" where needed in contrib/gregbook to quiet
-    compiler complaints about unused pointers.
-  Split a long output string in contrib/gregbook/rpng2-x.c.
-  Added "PNG_SET_OPTION" requirement for sRGB chunk support to pnglibconf.dfa,
-    Needed for write-only support (John Bowler).
-  Changed "if defined(__ARM_NEON__)" to
-    "if (defined(__ARM_NEON__) || defined(__ARM_NEON))" (James Wu).
-  Fixed clang no-warning builds: png_digit was defined but never used.
-    
-Version 1.6.13beta02 [July 21, 2014]
-  Fixed an incorrect separator ("/" should be "\") in scripts/makefile.vcwin32
-    (bug report from Wolfgang S. Kechel).  Bug was introduced in libpng-1.6.11.
-    Also fixed makefile.bc32, makefile.bor, makefile.msc, makefile.intel, and
-    makefile.tc3 similarly.
-
-Version 1.6.13beta03 [August 3, 2014]
-  Removed scripts/makefile.elf. It has not worked since libpng-1.5.0beta14
-    due to elimination of the PNG_FUNCTION_EXPORT and PNG_DATA_EXPORT
-    definitions from pngconf.h.
-  Ensure that CMakeLists.txt makes the target "lib" directory before making
-    symbolic link into it (SourceForge bug report #226 by Rolf Timmermans).
-
-Version 1.6.13beta04 [August 8, 2014]
-  Added opinion that the ECCN (Export Control Classification Number) for
-    libpng is EAR99 to the README file.
-  Eliminated use of "$<" in makefile explicit rules, when copying
-    $PNGLIBCONF_H_PREBUILT.  This does not work on some versions of make;
-    bug introduced in libpng version 1.6.11.
-
-Version 1.6.13rc01 [August 14, 2014]
-  Made "ccopts" agree with "CFLAGS" in scripts/makefile.hp* and makefile.*sunu
-
-Version 1.6.13 [August 21, 2014]
-  No changes.
-
-Version 1.6.14beta01 [September 14, 2014]
-  Guard usage of png_ptr->options with #ifdef PNG_SET_OPTION_SUPPORTED.
-  Do not build contrib/tools/pngfix.c when PNG_SETJMP_NOT_SUPPORTED,
-    to allow "make" to complete without setjmp support (bug report by
-    Claudio Fontana)
-  Add "#include <setjmp.h>" to contrib/tools/pngfix.c (John Bowler)
-
-Version 1.6.14beta02 [September 18, 2014]
-  Use nanosleep() instead of usleep() in contrib/gregbook/rpng2-x.c
-    because usleep() is deprecated.
-  Define usleep() in contrib/gregbook/rpng2-x.c if not already defined
-    in unistd.h and nanosleep() is not available; fixes error introduced
-    in libpng-1.6.13.
-  Disable floating point exception handling in pngvalid.c when
-    PNG_FLOATING_ARITHMETIC is not supported (bug report by "zootus
-    at users.sourceforge.net").
-
-Version 1.6.14beta03 [September 19, 2014]
-  Define FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in pngvalid.c if not
-    already defined.  Revert floating point exception handling in pngvalid.c
-    to version 1.6.14beta01 behavior.
-
-Version 1.6.14beta04 [September 27, 2014]
-  Fixed incorrect handling of the iTXt compression flag in pngrutil.c
-    (bug report by Shunsaku Hirata).  Bug was introduced in libpng-1.6.0.
-
-Version 1.6.14beta05 [October 1, 2014]
-  Added "option READ_iCCP enables READ_COMPRESSED_TEXT" to pnglibconf.dfa
-
-Version 1.6.14beta06 [October 5, 2014]
-  Removed unused "text_len" parameter from private function png_write_zTXt().
-  Conditionally compile some code in png_deflate_claim(), when
-    PNG_WARNINGS_SUPPORTED and PNG_ERROR_TEXT_SUPPORTED are disabled.
-  Replaced repeated code in pngpread.c with PNG_PUSH_SAVE_BUFFER_IF_FULL.
-  Added "chunk iTXt enables TEXT" and "chunk zTXt enables TEXT"
-    to pnglibconf.dfa.
-  Removed "option READ_COMPRESSED_TEXT enables READ_TEXT" from pnglibconf.dfa,
-    to make it possible to configure a libpng that supports iCCP but not TEXT.
-
-Version 1.6.14beta07 [October 7, 2014]
-  Removed "option WRITE_COMPRESSED_TEXT enables WRITE_TEXT" from pnglibconf.dfa
-  Only mark text chunks as written after successfully writing them.
-
-Version 1.6.14rc01 [October 15, 2014]
-  Fixed some typos in comments.
-
-Version 1.6.14rc02 [October 17, 2014]
-  Changed png_convert_to_rfc_1123() to png_convert_to_rfc_1123_buffer()
-    in the manual, to reflect the change made in libpng-1.6.0.
-  Updated README file to explain that direct access to the png_struct
-    and info_struct members has not been permitted since libpng-1.5.0.
-
-Version 1.6.14 [October 23, 2014]
-  No changes.
-
-Version 1.6.15beta01 [October 29, 2014]
-  Changed "if (!x)" to "if (x == 0)" and "if (x)" to "if (x != 0)"
-  Simplified png_free_data().
-  Added missing "ptr = NULL" after some instances of png_free().
-
-Version 1.6.15beta02 [November 1, 2014]
-  Changed remaining "if (!x)" to "if (x == 0)" and "if (x)" to "if (x != 0)"
-
-Version 1.6.15beta03 [November 3, 2014]
-  Added PNG_USE_ARM_NEON configuration flag (Marcin Juszkiewicz).
-
-Version 1.6.15beta04 [November 4, 2014]
-  Removed new PNG_USE_ARM_NEON configuration flag and made a one-line
-    revision to configure.ac to support ARM on aarch64 instead (John Bowler).
-
-Version 1.6.15beta05 [November 5, 2014]
-  Use png_get_libpng_ver(NULL) instead of PNG_LIBPNG_VER_STRING in
-    example.c, pngtest.c, and applications in the contrib directory.
-  Fixed an out-of-range read in png_user_version_check() (Bug report from
-    Qixue Xiao, CVE-2015-8540).
-  Simplified and future-proofed png_user_version_check().
-  Fixed GCC unsigned int->float warnings. Various versions of GCC
-    seem to generate warnings when an unsigned value is implicitly
-    converted to double. This is probably a GCC bug but this change
-    avoids the issue by explicitly converting to (int) where safe.
-  Free all allocated memory in pngimage. The file buffer cache was left
-    allocated at the end of the program, harmless but it causes memory
-    leak reports from clang.
-  Fixed array size calculations to avoid warnings. At various points
-    in the code the number of elements in an array is calculated using
-    sizeof.  This generates a compile time constant of type (size_t) which
-    is then typically assigned to an (unsigned int) or (int). Some versions
-    of GCC on 64-bit systems warn about the apparent narrowing, even though
-    the same compiler does apparently generate the correct, in-range,
-    numeric constant.  This adds appropriate, safe, casts to make the
-    warnings go away.
-
-Version 1.6.15beta06 [November 6, 2014]
-  Reverted use png_get_libpng_ver(NULL) instead of PNG_LIBPNG_VER_STRING
-    in the manual, example.c, pngtest.c, and applications in the contrib
-    directory.  It was incorrect advice.
-
-Version 1.6.15beta07 [November 7, 2014]
-  Removed #ifdef PNG_16BIT_SUPPORTED/#endif around png_product2(); it is
-    needed by png_reciprocal2().
-  Added #ifdef PNG_16BIT_SUPPORTED/#endif around png_log16bit() and
-    png_do_swap().
-  Changed all "#endif /* PNG_FEATURE_SUPPORTED */" to "#endif /* FEATURE */"
-
-Version 1.6.15beta08 [November 8, 2014]
-  More housecleaning in *.h
-
-Version 1.6.15rc01 [November 13, 2014]
-
-Version 1.6.15rc02 [November 14, 2014]
-  The macros passed in the command line to Borland make were ignored if
-    similarly-named macros were already defined in makefiles. This behavior
-    is different from POSIX make and other make programs.  Surround the
-    macro definitions with ifndef guards (Cosmin).
-
-Version 1.6.15rc03 [November 16, 2014]
-  Added "-D_CRT_SECURE_NO_WARNINGS" to CFLAGS in scripts/makefile.vcwin32.
-  Removed the obsolete $ARCH variable from scripts/makefile.darwin.
-
-Version 1.6.15 [November 20, 2014]
-  No changes.
-
-Version 1.6.16beta01 [December 14, 2014]
-  Added ".align 2" to arm/filter_neon.S to support old GAS assemblers that
-    don't do alignment correctly.
-  Revised Makefile.am and scripts/symbols.dfn to work with MinGW/MSYS
-    (Bob Friesenhahn).
-
-Version 1.6.16beta02 [December 15, 2014]
-  Revised Makefile.am and scripts/*.dfn again to work with MinGW/MSYS;
-    renamed scripts/*.dfn to scripts/*.c (John Bowler).
-
-Version 1.6.16beta03 [December 21, 2014]
-  Quiet a "comparison always true" warning in pngstest.c (John Bowler).
-
-Version 1.6.16rc01 [December 21, 2014]
-  Restored a test on width that was removed from png.c at libpng-1.6.9
-    (Bug report by Alex Eubanks, CVE-2015-0973).
-
-Version 1.6.16rc02 [December 21, 2014]
-  Undid the update to pngrutil.c in 1.6.16rc01.
-
-Version 1.6.16rc03 [December 21, 2014]
-  Fixed an overflow in png_combine_row() with very wide interlaced images
-    (Bug report and fix by John Bowler, CVE-2014-9495).
-
-Version 1.6.16 [December 22, 2014]
-  No changes.
-
-Version 1.6.17beta01 [January 29, 2015]
-  Removed duplicate PNG_SAFE_LIMITS_SUPPORTED handling from pngconf.h
-  Corrected the width limit calculation in png_check_IHDR().
-  Removed user limits from pngfix. Also pass NULL pointers to
-    png_read_row to skip the unnecessary row de-interlace stuff.
-  Added testing of png_set_packing() to pngvalid.c
-  Regenerated configure scripts in the *.tar distributions with libtool-2.4.4
-  Implement previously untested cases of libpng transforms in pngvalid.c
-  Fixed byte order in png_do_read_filler() with 16-bit input. Previously
-    the high and low bytes of the filler, from png_set_filler() or from
-    png_set_add_alpha(), were read in the wrong order.
-  Made the check for out-of-range values in png_set_tRNS() detect
-    values that are exactly 2^bit_depth, and work on 16-bit platforms.
-  Merged some parts of libpng-1.6.17beta01 and libpng-1.7.0beta47.
-  Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
-    pngset.c to avoid warnings about dead code.
-  Added "& 0xff" to many instances of expressions that are typecast
-    to (png_byte), to avoid Coverity warnings.
-
-Version 1.6.17beta02 [February 7, 2015]
-  Work around one more Coverity-scan dead-code warning.
-  Do not build png_product2() when it is unused.
-
-Version 1.6.17beta03 [February 17, 2015]
-  Display user limits in the output from pngtest.
-  Eliminated the PNG_SAFE_LIMITS macro and restored the 1-million-column
-    and 1-million-row default limits in pnglibconf.dfa, that can be reset
-    by the user at build time or run time.  This provides a more robust
-    defense against DOS and as-yet undiscovered overflows.
-
-Version 1.6.17beta04 [February 21, 2015]
-  Added PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED macro, on by default.
-  Allow user to call png_get_IHDR() with NULL arguments (Reuben Hawkins).
-  Rebuilt configure scripts with automake-1.15 and libtool-2.4.6
-
-Version 1.6.17beta05 [February 25, 2015]
-  Restored compiling of png_reciprocal2 with PNG_NO_16BIT.
-
-Version 1.6.17beta06 [February 27, 2015]
-  Moved png_set_filter() prototype into a PNG_WRITE_SUPPORTED block
-    of png.h.
-  Avoid runtime checks when converting integer to png_byte with
-    Visual Studio (Sergey Kosarevsky)
-
-Version 1.6.17rc01 [March 4, 2015]
-  No changes.
-
-Version 1.6.17rc02 [March 9, 2015]
-  Removed some comments that the configure script did not handle
-    properly from scripts/pnglibconf.dfa and pnglibconf.h.prebuilt.
-  Free the unknown_chunks structure even when it contains no data.
-
-Version 1.6.17rc03 [March 12, 2015]
-  Updated CMakeLists.txt to add OSX framework, change YES/NO to ON/OFF
-    for consistency, and remove some useless tests (Alexey Petruchik).
-
-Version 1.6.17rc04 [March 16, 2015]
-  Remove pnglibconf.h, pnglibconf.c, and pnglibconf.out instead of
-    pnglibconf.* in "make clean" (Cosmin).
-  Fix bug in calculation of maxbits, in png_write_sBIT, introduced
-    in libpng-1.6.17beta01 (John Bowler).
-
-Version 1.6.17rc05 [March 21, 2015]
-  Define PNG_FILTER_* and PNG_FILTER_VALUE_* in png.h even when WRITE
-    is not supported (John Bowler).  This fixes an error introduced in
-    libpng-1.6.17beta06.
-  Reverted "& 0xff" additions of version 1.6.17beta01. Libpng passes
-    the Coverity scan without them.
-
-Version 1.6.17rc06 [March 23, 2015]
-  Remove pnglibconf.dfn and pnglibconf.pre with "make clean".
-  Reformatted some "&0xff" instances to "& 0xff".
-  Fixed simplified 8-bit-linear to sRGB alpha. The calculated alpha
-    value was wrong.  It's not clear if this affected the final stored
-    value; in the obvious code path the upper and lower 8-bits of the
-    alpha value were identical and the alpha was truncated to 8-bits
-    rather than dividing by 257 (John Bowler).
-
-Version 1.6.17 [March 26, 2015]
-  No changes.
-
-Version 1.6.18beta01 [April 1, 2015]
-  Removed PNG_SET_CHUNK_[CACHE|MALLOC]_LIMIT_SUPPORTED macros.  They
-    have been combined with PNG_SET_USER_LIMITS_SUPPORTED (resolves
-    bug report by Andrew Church).
-  Fixed rgb_to_gray checks and added tRNS checks to pngvalid.c.  This
-    fixes some arithmetic errors that caused some tests to fail on
-    some 32-bit platforms (Bug reports by Peter Breitenlohner [i686]
-    and Petr Gajdos [i586]).
-
-Version 1.6.18beta02 [April 26, 2015]
-  Suppressed some warnings from the Borland C++ 5.5.1/5.82 compiler
-    (Bug report by Viktor Szakats).
-
-Version 1.6.18beta03 [May 6, 2015]
-  Replaced "unexpected" with an integer (0xabadca11) in pngset.c
-    where a long was expected, to avoid a compiler warning when PNG_DEBUG > 1.
-  Added contrib/examples/simpleover.c, to demonstrate how to handle
-    alpha compositing of multiple images, using the "simplified API"
-    and an example PNG generation tool, contrib/examples/genpng.c
-    (John Bowler).
-
-Version 1.6.18beta04 [May 20, 2015]
-  PNG_RELEASE_BUILD replaces tests where the code depended on the build base
-    type and can be defined on the command line, allowing testing in beta
-    builds (John Bowler).
-  Avoid Coverity issue 80858 (REVERSE NULL) in pngtest.c PNG_DEBUG builds.
-  Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
-    report from Christopher Ferris).
-
-Version 1.6.18beta05 [May 31, 2015]
-  Backport filter selection code from libpng-1.7.0beta51, to combine
-    sub_row, up_row, avg_row, and paeth_row into try_row and tst_row.
-  Changed png_voidcast(), etc., to voidcast(), etc., in contrib/tools/pngfix.c
-    to avoid confusion with the libpng private macros.
-  Fixed old cut&paste bug in the weighted filter selection code in
-    pngwutil.c, introduced in libpng-0.95, March 1997.
-
-Version 1.6.18beta06 [June 1, 2015]
-  Removed WRITE_WEIGHTED_FILTERED code, to save a few kbytes of the
-    compiled library size. It never worked properly and as far as we can
-    tell, no one uses it. The png_set_filter_heuristics() and
-    png_set_filter_heuristics_fixed() APIs are retained but deprecated
-    and do nothing.
-
-Version 1.6.18beta07 [June 6, 2015]
-  Removed non-working progressive reader 'skip' function. This
-    function has apparently never been used. It was implemented
-    to support back-door modification of png_struct in libpng-1.4.x
-    but (because it does nothing and cannot do anything) was apparently
-    never tested (John Bowler).
-  Fixed cexcept.h in which GCC 5 now reports that one of the auto
-    variables in the Try macro needs to be volatile to prevent value
-    being lost over the setjmp (John Bowler).
-  Fixed NO_WRITE_FILTER and -Wconversion build breaks (John Bowler).
-  Fix g++ build breaks (John Bowler).
-  Quieted some Coverity issues in pngfix.c, png-fix-itxt.c, pngvalid.c,
-    pngstest.c, and pngimage.c. Most seem harmless, but png-fix-itxt
-    would only work with iTXt chunks with length 255 or less.
-  Added #ifdef's to contrib/examples programs so people don't try
-    to compile them without the minimum required support enabled
-    (suggested by Flavio Medeiros).
-
-Version 1.6.18beta08 [June 30, 2015]
-  Eliminated the final two Coverity defects (insecure temporary file
-    handling in contrib/libtests/pngstest.c; possible overflow of
-    unsigned char in contrib/tools/png-fix-itxt.c). To use the "secure"
-    file handling, define PNG_USE_MKSTEMP, otherwise "tmpfile()" will
-    be used.
-  Removed some unused WEIGHTED_FILTER macros from png.h and pngstruct.h
-
-Version 1.6.18beta09 [July 5, 2015]
-  Removed some useless typecasts from contrib/tools/png-fix-itxt.c
-  Fixed a new signed-unsigned comparison in pngrtran.c (Max Stepin).
-  Replaced arbitrary use of 'extern' with #define PNG_LINKAGE_*.  To
-    preserve API compatibility, the new defines all default to "extern"
-    (requested by Jan Nijtmans).
-
-Version 1.6.18rc01 [July 9, 2015]
-  Belatedly added Mans Rullgard and James Yu to the list of Contributing
-    Authors.
-
-Version 1.6.18rc02 [July 12, 2015]
-  Restored unused FILTER_HEURISTIC macros removed at libpng-1.6.18beta08
-    to png.h to avoid compatibility warnings.
-
-Version 1.6.18rc03 [July 15, 2015]
-  Minor changes to the man page
-
-Version 1.6.18 [July 23, 2015]
-  No changes.
-
-Version 1.6.19beta01 [July 30, 2015]
-  Updated obsolete information about the simplified API macros in the
-    manual pages (Bug report by Arc Riley).
-  Avoid potentially dereferencing NULL info_ptr in png_info_init_3().
-  Rearranged png.h to put the major sections in the same order as
-    in libpng17.
-  Eliminated unused PNG_COST_SHIFT, PNG_WEIGHT_SHIFT, PNG_COST_FACTOR, and
-    PNG_WEIGHT_FACTOR macros.
-  Suppressed some warnings from the Borland C++ 5.5.1/5.82 compiler
-    (Bug report by Viktor Szakats).  Several warnings remain and are
-    unavoidable, where we test for overflow.
-  Fixed potential leak of png_pixels in contrib/pngminus/pnm2png.c
-  Fixed uninitialized variable in contrib/gregbook/rpng2-x.c
-
-Version 1.6.19beta02 [August 19, 2015]
-  Moved config.h.in~ from the "libpng_autotools_files" list to the
-    "libpng_autotools_extra" list in autogen.sh because it was causing a
-    false positive for missing files (bug report by Robert C. Seacord).
-  Removed unreachable "break" statements in png.c, pngread.c, and pngrtran.c
-    to suppress clang warnings (Bug report by Viktor Szakats).
-  Fixed some bad links in the man page.
-  Changed "n bit" to "n-bit" in comments.
-  Added signed/unsigned 16-bit safety net. This removes the dubious
-    0x8000 flag definitions on 16-bit systems. They aren't supported
-    yet the defs *probably* work, however it seems much safer to do this
-    and be advised if anyone, contrary to advice, is building libpng 1.6
-    on a 16-bit system. It also adds back various switch default clauses
-    for GCC; GCC errors out if they are not present (with an appropriately
-    high level of warnings).
-  Safely convert num_bytes to a png_byte in png_set_sig_bytes() (Robert
-    Seacord).
-  Fixed the recently reported 1's complement security issue by replacing
-    the value that is illegal in the PNG spec, in both signed and unsigned
-    values, with 0. Illegal unsigned values (anything greater than or equal
-    to  0x80000000) can still pass through, but since these are not illegal
-    in ANSI-C (unlike 0x80000000 in the signed case) the checking that
-    occurs later can catch them (John Bowler).
-
-Version 1.6.19beta03 [September 26, 2015]
-  Fixed png_save_int_32 when int is not 2's complement (John Bowler).
-  Updated libpng16 with all the recent test changes from libpng17,
-    including changes to pngvalid.c to ensure that the original,
-    distributed, version of contrib/visupng/cexcept.h can be used
-    (John Bowler).
-  pngvalid contains the correction to the use of SAVE/STORE_
-    UNKNOWN_CHUNKS; a bug revealed by changes in libpng 1.7. More
-    tests contain the --strict option to detect warnings and the
-    pngvalid-standard test has been corrected so that it does not
-    turn on progressive-read. There is a separate test which does
-    that. (John Bowler)
-  Also made some signed/unsigned fixes.
-  Make pngstest error limits version specific. Splitting the machine
-    generated error structs out to a file allows the values to be updated
-    without changing pngstest.c itself. Since libpng 1.6 and 1.7 have
-    slightly different error limits this simplifies maintenance. The
-    makepngs.sh script has also been updated to more accurately reflect
-    current problems in libpng 1.7 (John Bowler).
-  Incorporated new test PNG files into make check.  tests/pngstest-*
-    are changed so that the new test files are divided into 8 groups by
-    gamma and alpha channel.  These tests have considerably better code
-    and pixel-value coverage than contrib/pngsuite; however,coverage is
-    still incomplete (John Bowler).
-  Removed the '--strict' in 1.6 because of the double-gamma-correction
-    warning, updated pngstest-errors.h for the errors detected with the
-    new contrib/testspngs PNG test files (John Bowler).
-
-Version 1.6.19beta04 [October 15, 2015]
-  Worked around rgb-to-gray issues in libpng 1.6.  The previous
-    attempts to ignore the errors in the code aren't quite enough to
-    deal with the 'channel selection' encoding added to libpng 1.7; abort.
-    pngvalid.c is changed to drop this encoding in prior versions.
-  Fixed 'pow' macros in pngvalid.c. It is legal for 'pow' to be a
-    macro, therefore the argument list cannot contain preprocessing
-    directives.  Make sure pow is a function where this happens. This is
-    a minimal safe fix, the issue only arises in non-performance-critical
-    code (bug report by Curtis Leach, fix by John Bowler).
-  Added sPLT support to pngtest.c
-
-Version 1.6.19rc01 [October 23, 2015]
-  No changes.
-
-Version 1.6.19rc02 [October 31, 2015]
-  Prevent setting or writing over-length PLTE chunk (Cosmin Truta).
-  Silently truncate over-length PLTE chunk while reading.
-  Libpng incorrectly calculated the output rowbytes when the application
-    decreased either the number of channels or the bit depth (or both) in
-    a user transform.  This was safe; libpng overallocated buffer space
-   (potentially by quite a lot; up to 4 times the amount required) but,
-   from 1.5.4 on, resulted in a png_error (John Bowler).
-
-Version 1.6.19rc03 [November 3, 2015]
-  Fixed some inconsequential cut-and-paste typos in png_set_cHRM_XYZ_fixed().
-  Clarified COPYRIGHT information to state explicitly that versions
-    are derived from previous versions.
-  Removed much of the long list of previous versions from png.h and
-    libpng.3.
-
-Version 1.6.19rc04 [November 5, 2015]
-  Fixed new bug with CRC error after reading an over-length palette
-    (bug report by Cosmin Truta) (CVE-2015-8126).
-
-Version 1.6.19 [November 12, 2015]
-  Cleaned up coding style in png_handle_PLTE().
-
-Version 1.6.20beta01 [November 20, 2015]
-  Avoid potential pointer overflow/underflow in png_handle_sPLT() and
-    png_handle_pCAL() (Bug report by John Regehr).
-
-Version 1.6.20beta02 [November 23, 2015]
-  Fixed incorrect implementation of png_set_PLTE() that uses png_ptr
-    not info_ptr, that left png_set_PLTE() open to the CVE-2015-8126
-    vulnerability.  Fixes CVE-2015-8472.
-
-Version 1.6.20beta03 [November 24, 2015]
-  Backported tests from libpng-1.7.0beta69.
-
-Version 1.6.20rc01 [November 26, 2015]
-  Fixed an error in handling of bad zlib CMINFO field in pngfix, found by
-    American Fuzzy Lop, reported by Brian Carpenter.  inflate() doesn't
-    immediately fault a bad CMINFO field; instead a 'too far back' error
-    happens later (at least some times).  pngfix failed to limit CMINFO to
-    the allowed values but then assumed that window_bits was in range,
-    triggering an assert. The bug is mostly harmless; the PNG file cannot
-    be fixed.
-
-Version 1.6.20rc02 [November 29, 2015]
-  In libpng 1.6 zlib initialization was changed to use the window size
-    in the zlib stream, not a fixed value. This causes some invalid images,
-    where CINFO is too large, to display 'correctly' if the rest of the
-    data is valid.  This provides a workaround for zlib versions where the
-    error arises (ones that support the API change to use the window size
-    in the stream).
-
-Version 1.6.20 [December 3, 2015]
-  No changes.
-
-Version 1.6.21beta01 [December 11, 2015]
-  Fixed syntax "$(command)" in tests/pngstest that some shells other than
-    bash could not parse (Bug report by Nelson Beebe). Use `command` instead.
-
-Version 1.6.21beta02 [December 14, 2015]
-  Moved png_check_keyword() from pngwutil.c to pngset.c
-  Removed LE/BE dependencies in pngvalid, to 'fix' the current problem
-    in the BigEndian tests by not testing it, making the BE code the same 
-    as the LE version.
-  Fixes to pngvalid for various reduced build configurations (eliminate unused
-    statics) and a fix for the case in rgb_to_gray when the digitize option
-    reduces graylo to 0, producing a large error.
-
-Version 1.6.21beta03 [December 18, 2015]
-  Widened the 'limit' check on the internally calculated error limits in
-    the 'DIGITIZE' case (the code used prior to 1.7 for rgb_to_gray error
-    checks) and changed the check to only operate in non-release builds
-    (base build type not RC or RELEASE.)
-  Fixed undefined behavior in pngvalid.c, undefined because
-    (png_byte) << shift is undefined if it changes the signed bit
-    (because png_byte is promoted to int). The libpng exported functions
-    png_get_uint_32 and png_get_uint_16 handle this. (Bug reported by
-    David Drysdale as a result of reports from UBSAN in clang 3.8).
-  This changes pngvalid to use BE random numbers; this used to produce
-    errors but these should not be fixed as a result of the previous changes.
-
-Version 1.6.21rc01 [January 4, 2016]
-  In projects/vstudio, combined readme.txt and WARNING into README.txt
-
-Version 1.6.21rc02 [January 7, 2016]
-  Relocated assert() in contrib/tools/pngfix.c, bug found by American
-    Fuzzy Lop, reported by Brian Carpenter.
-  Marked 'limit' UNUSED in transform_range_check().  This only affects
-    release builds.
-
-Version 1.6.21 [January 15, 2016]
-  Worked around a false-positive Coverity issue in pngvalid.c.
-
-Version 1.6.22beta01 [January 23, 2016]
-  Changed PNG_USE_MKSTEMP to __COVERITY__ to select alternate
-    "tmpfile()" implementation in contrib/libtests/pngstest.c
-  Fixed NO_STDIO build of pngunknown.c to skip calling png_init_io()
-    if there is no stdio.h support.
-  Added a png_image_write_to_memory() API and a number of assist macros
-    to allow an application that uses the simplified API write to bypass
-    stdio and write directly to memory.
-  Added some warnings (png.h) and some check code to detect *possible*
-    overflow in the ROW_STRIDE and simplified image SIZE macros.  This
-    disallows image width/height/format that *might* overflow.  This is
-    a quiet API change that limits in-memory image size (uncompressed) to
-    less than 4GByte and image row size (stride) to less than 2GByte.
-  Revised workaround for false-positive Coverity issue in pngvalid.c.
-
-Version 1.6.22beta02 [February 8, 2016]
-  Only use exit(77) in configure builds.
-  Corrected error in PNG_IMAGE_PNG_SIZE_MAX. This new macro underreported
-    the palette size because it failed to take into account that the memory
-    palette has to be expanded to full RGB when it is written to PNG.
-  Updated CMakeLists.txt, added supporting scripts/gen*.cmake.in
-    and test.cmake.in (Roger Leigh).
-  Relaxed limit checks on gamma values in pngrtran.c. As suggested in
-    the comments gamma values outside the range currently permitted
-    by png_set_alpha_mode are useful for HDR data encoding.  These values
-    are already permitted by png_set_gamma so it is reasonable caution to
-    extend the png_set_alpha_mode range as HDR imaging systems are starting
-    to emerge.
-
-Version 1.6.22beta03 [March 9, 2016]
-  Added a common-law trademark notice and export control information
-    to the LICENSE file, png.h, and the man page.
-  Restored "& 0xff" in png_save_uint_16() and png_save_uint_32() that
-    were accidentally removed from libpng-1.6.17. 
-  Changed PNG_INFO_cHNK and PNG_FREE_cHNK from 0xnnnn to 0xnnnnU in png.h
-    (Robert C. Seacord).
-  Removed dubious "#if INT_MAX" test from png.h that was added to
-    libpng-1.6.19beta02 (John Bowler).
-  Add ${INCLUDES} in scripts/genout.cmake.in (Bug report by Nixon Kwok).
-  Updated LICENSE to say files in the contrib directory are not
-    necessarily under the libpng license, and that some makefiles have
-    other copyright owners.
-  Added INTEL-SSE2 support (Mike Klein and Matt Sarett, Google, Inc.).
-  Made contrib/libtests/timepng more robust.  The code no longer gives
-    up/fails on invalid PNG data, it just skips it (with error messages).
-    The code no longer fails on PNG files with data beyond IEND.  Options
-    exist to use png_read_png (reading the whole image, not by row) and, in
-    that case, to apply any of the supported transforms.  This makes for
-    more realistic testing; the decoded data actually gets used in a
-    meaningful fashion (John Bowler).
-  Fixed some misleading indentation (Krishnaraj Bhat).
-
-Version 1.6.22beta04 [April 5, 2016]
-  Force GCC compilation to C89 if needed (Dagobert Michelsen).
-  SSE filter speed improvements for bpp=3:
-    memcpy-free implementations of load3() / store3().
-    call load3() only when needed at the end of a scanline.
-
-Version 1.6.22beta05 [April 27, 2016]
-  Added PNG_FAST_FILTERS macro (defined as
-    PNG_FILTER_NONE|PNG_FILTER_SUB|PNG_FILTER_UP).
-  Various fixes for contrib/libtests/timepng.c
-  Moved INTEL-SSE code from pngpriv.h into contrib/intel/intel_sse.patch.
-  Fixed typo (missing underscore) in #define PNG_READ_16_TO_8_SUPPORTED
-    (Bug report by Y.Ohashik).
-
-Version 1.6.22beta06 [May 5, 2016]
-  Rebased contrib/intel_sse.patch.
-  Quieted two Coverity issues in contrib/libtests/timepng.c.
-  Fixed issues with scripts/genout.cmake.in (David Capello, Nixon Kwok):
-    Added support to use multiple directories in ZLIBINCDIR variable,
-    Fixed CMAKE_C_FLAGS with multiple values when genout is compiled on MSVC,
-    Fixed pnglibconf.c compilation on OS X including the sysroot path.
-
-Version 1.6.22rc01 [May 14, 2016]
-  No changes.
-
-Version 1.6.22rc02 [May 16, 2016]
-  Removed contrib/timepng from default build; it does not build on platforms
-    that don't supply clock_gettime().
-
-Version 1.6.22rc03 [May 17, 2016]
-  Restored contrib/timepng to default build but check for the presence
-    of clock_gettime() in configure.ac and Makefile.am.
-
-Version 1.6.22 [May 26, 2016]
-  No changes.
-
-Version 1.6.23beta01 [May 29, 2016]
-  Stop a potential memory leak in png_set_tRNS() (Bug report by Ted Ying).
-  Fixed the progressive reader to handle empty first IDAT chunk properly
-    (patch by Timothy Nikkel).  This bug was introduced in libpng-1.6.0 and
-    only affected the libpng16 branch.
-  Added tests in pngvalid.c to check zero-length IDAT chunks in various
-    positions.  Fixed the sequential reader to handle these more robustly
-    (John Bowler).
-
-Version 1.6.23rc01 [June 2, 2016]
-  Corrected progressive read input buffer in pngvalid.c. The previous version
-    the code invariably passed just one byte at a time to libpng.  The intent
-    was to pass a random number of bytes in the range 0..511.
-  Moved sse2 prototype from pngpriv.h to contrib/intel/intel_sse.patch.
-  Added missing ")" in pngerror.c (Matt Sarrett).
-
-Version 1.6.23rc02 [June 4, 2016]
-  Fixed undefined behavior in png_push_save_buffer(). Do not call
-    memcpy() with a null source, even if count is zero (Leon Scroggins III).
-
-Version 1.6.23 [June 9, 2016]
-  Fixed bad link to RFC2083 in png.5 (Nikola Forro).
-
-Version 1.6.24beta01 [June 11, 2016]
-  Avoid potential overflow of the PNG_IMAGE_SIZE macro.  This macro
-    is not used within libpng, but is used in some of the examples.
-
-Version 1.6.24beta02 [June 23, 2016]
-  Correct filter heuristic overflow handling. This was broken when the
-    write filter code was moved out-of-line; if there is a single filter and
-    the heuristic sum overflows the calculation of the filtered line is not
-    completed.  In versions prior to 1.6 the code was duplicated in-line
-    and the check not performed, so the filter operation completed; however,
-    in the multi-filter case where the sum is performed the 'none' filter would
-    be selected if all the sums overflowed, even if it wasn't in the filter
-    list.  The fix to the first problem is simply to provide PNG_SIZE_MAX as
-    the current lmins sum value; this means the sum can never exceed it and
-    overflows silently.  A reasonable compiler that does choose to inline
-    the code will simply eliminate the sum check.
-  The fix to the second problem is to use high precision arithmetic (this is
-    implemented in 1.7), however a simple safe fix here is to chose the lowest
-    numbered filter in the list from png_set_filter (this only works if the
-    first problem is also fixed) (John Bowler).
-  Use a more efficient absolute value calculation on SSE2 (Matthieu Darbois).
-  Fixed the case where PNG_IMAGE_BUFFER_SIZE can overflow in the application
-    as a result of the application using an increased 'row_stride'; previously
-    png_image_finish_read only checked for overflow on the base calculation of
-    components.  (I.e. it checked for overflow of a 32-bit number on the total
-    number of pixel components in the output format, not the possibly padded row
-    length and not the number of bytes, which for linear formats is twice the
-    number of components.)
-  MSVC does not like '-(unsigned)', so replaced it with 0U-(unsigned)
-  MSVC does not like (uInt) = -(unsigned) (i.e. as an initializer), unless
-    the conversion is explicitly invoked by a cast.
-  Put the SKIP definition in the correct place. It needs to come after the
-    png.h include (see all the other .c files in contrib/libtests) because it
-    depends on PNG_LIBPNG_VER.
-  Removed the three compile warning options from the individual project
-    files into the zlib.props globals.  It increases the warning level from 4
-    to All and adds a list of the warnings that need to be turned off.  This is
-    semi-documentary; the intent is to tell libpng users which warnings have
-    been examined and judged non-fixable at present.  The warning about
-    structure padding is fixable, but it would be a signficant change (moving
-    structure members around).
-
-Version 1.6.24beta03 [July 4, 2016]
-  Optimized absolute value calculation in filter selection, similar to
-    code in the PAETH decoder in pngrutil.c. Build with PNG_USE_ABS to
-    use this.
-  Added pngcp to the build together with a pngcp.dfa configuration test.
-  Added high resolution timing to pngcp.
-  Added "Common linking failures" section to INSTALL.
-  Relocated misplaced #endif in png.c sRGB profile checking.
-  Fixed two Coverity issues in pngcp.c.
-
-Version 1.6.24beta04 [July 8, 2016]
-  Avoid filter-selection heuristic sum calculations in cases where only one
-    filter is a candidate for selection. This trades off code size (added
-    private png_setup_*_row_only() functions) for speed.
-
-Version 1.6.24beta05 [July 13, 2016]
-  Fixed some indentation to comply with our coding style.
-  Added contrib/tools/reindent.
-
-Version 1.6.24beta06 [July 18, 2016]
-  Fixed more indentation to comply with our coding style.
-  Eliminated unnecessary tests of boolean png_isaligned() vs 0.
-
-Version 1.6.24rc01 [July 25, 2016]
-  No changes.
-
-Version 1.6.24rc02 [August 1, 2016]
-  Conditionally compile SSE2 headers in contrib/intel/intel_sse.patch
-  Conditionally compile png_decompress_chunk().
-
-Version 1.6.24rc03 [August 2, 2016]
-  Conditionally compile ARM_NEON headers in pngpriv.h
-  Updated contrib/intel/intel_sse.patch
-
-Version 1.6.24[August 4, 2016]
-  No changes.
-
-Version 1.6.25beta01 [August 12, 2016]
-  Reject oversized iCCP profile immediately.
-  Cleaned up PNG_DEBUG compile of pngtest.c.
-  Conditionally compile png_inflate().
-
-Version 1.6.25beta02 [August 18, 2016]
-  Don't install pngcp; it conflicts with pngcp in the pngtools package.
-  Minor editing of INSTALL, (whitespace, added copyright line)
-
-Version 1.6.25rc01 [August 24, 2016]
-  No changes.
-
-Version 1.6.25rc02 [August 29, 2016]
-  Added MIPS support (Mandar Sahastrabuddhe <Mandar.Sahastrabuddhe@imgtec.com>).
-  Only the UP filter is currently implemented.
-
-Version 1.6.25rc03 [August 29, 2016]
-  Rebased contrib/intel/intel_sse.patch after the MIPS implementation.
-
-Version 1.6.25rc04 [August 30, 2016]
-  Added MIPS support for SUB, AVG, and PAETH filters (Mandar Sahastrabuddhe).
-
-Version 1.6.25rc05 [August 30, 2016]
-  Rebased contrib/intel/intel_sse.patch after the MIPS implementation update..
-
-Version 1.6.25 [September 1, 2016]
-  No changes.
-
-Version 1.6.26beta01 [September 26, 2016]
-  Fixed handling zero length IDAT in pngfix (bug report by Agostino Sarubbo,
-    bugfix by John Bowler).
-  Do not issue a png_error() on read in png_set_pCAL() because png_handle_pCAL
-    has allocated memory that libpng needs to free.
-  Conditionally compile png_set_benign_errors() in pngread.c and pngtest.c
-  Issue a png_benign_error instead of a png_error on ADLER32 mismatch
-    while decoding compressed data chunks.
-  Changed PNG_ZLIB_VERNUM to ZLIB_VERNUM in pngpriv.h, pngstruct.h, and
-    pngrutil.c.
-  If CRC handling of critical chunks has been set to PNG_CRC_QUIET_USE,
-    ignore the ADLER32 checksum in the IDAT chunk as well as the chunk CRCs.
-  Issue png_benign_error() on ADLER32 checksum mismatch instead of png_error().
-  Add tests/badcrc.png and tests/badadler.png to tests/pngtest.
-  Merged pngtest.c with libpng-1.7.0beta84/pngtest.c
-
-Version 1.6.26beta02 [October 1, 2016]
-  Updated the documentation about CRC and ADLER32 handling.
-  Quieted 117 warnings from clang-3.8 in pngtrans.c, pngread.c,
-     pngwrite.c, pngunknown.c, and pngvalid.c.
-  Quieted 58 (out of 144) -Wconversion compiler warnings by changing
-    flag definitions in pngpriv.h from 0xnnnn to 0xnnnnU and trivial changes
-    in png.c, pngread.c, and pngwutil.c.
-
-Version 1.6.26beta03 [October 2, 2016]
-  Removed contrib/libtests/*.orig and *.rej that slipped into the tarballs.
-  Quieted the 86 remaining -Wconversion compiler warnings by
-    revising the png_isaligned() macro and trivial changes in png.c,
-    pngerror.c, pngget.c, pngmem.c, pngset.c, pngrtran.c, pngrutil.c,
-    pngwtran.c, pngwrite.c, and pngwutil.c.
-
-Version 1.6.26beta04 [October 3, 2016]
-  Quieted (bogus?) clang warnings about "absolute value has no effect"
-    when PNG_USE_ABS is defined.
-  Fixed offsets in contrib/intel/intel_sse.patch
-
-Version 1.6.26beta05 [October 6, 2016]
-  Changed integer constant 4294967294 to unsigned 4294967294U in pngconf.h
-    to avoid a signed/unsigned compare in the preprocessor.
-
-Version 1.6.26beta06 [October 7, 2016]
-  Use zlib-1.2.8.1 inflateValidate() instead of inflateReset2() to
-    optionally avoid ADLER32 evaluation.
-
-Version 1.6.26rc01 [October 12, 2016]
-  No changes.
-
-Version 1.6.26 [October 20, 2016]
-  Cosmetic change, "ptr != 0" to "ptr != NULL" in png.c and pngrutil.c
-  Despammed email addresses (replaced "@" with " at ").
-
-Version 1.6.27beta01 [November 2, 2016]
-  Restrict the new ADLER32-skipping to IDAT chunks.  It broke iCCP chunk
-    handling: an erroneous iCCP chunk would throw a png_error and reject the
-    entire PNG image instead of rejecting just the iCCP chunk with a warning,
-    if built with zlib-1.2.8.1.
-
-Version 1.6.27rc01 [December 27, 2016]
-  Control ADLER32 checking with new PNG_IGNORE_ADLER32 option. Fixes
-    an endless loop when handling erroneous ADLER32 checksums; bug
-    introduced in libpng-1.6.26.
-  Removed the use of a macro containing the pre-processor 'defined'
-    operator.  It is unclear whether this is valid; a macro that
-    "generates" 'defined' is not permitted, but the use of the word
-    "generates" within the C90 standard seems to imply more than simple
-    substitution of an expression itself containing a well-formed defined
-    operation.
-  Added ARM support to CMakeLists.txt (Andreas Franek).
-
-Version 1.6.27 [December 29, 2016]
-  Fixed a potential null pointer dereference in png_set_text_2() (bug report
-    and patch by Patrick Keshishian, CVE-2016-10087).
-
-Version 1.6.28rc01 [January 3, 2017]
-  Fixed arm/aarch64 detection in CMakeLists.txt (Gianfranco Costamagna).
-  Added option to Cmake build allowing a custom location of zlib to be
-    specified in a scenario where libpng is being built as a subproject
-    alongside zlib by another project (Sam Serrels).
-  Changed png_ptr->options from a png_byte to png_uint_32, to accomodate
-    up to 16 options.
-
-Version 1.6.28rc02 [January 4, 2017]
-  Added "include(GNUInstallDirs)" to CMakeLists.txt (Gianfranco Costamagna).
-  Moved SSE2 optimization code into the main libpng source directory.
-    Configure libpng with "configure --enable-intel-sse" or compile
-    libpng with "-DPNG_INTEL_SSE" in CPPFLAGS to enable it.
-
-Version 1.6.28rc03 [January 4, 2017]
-  Backed out the SSE optimization and last CMakeLists.txt to allow time for QA.
-
-Version 1.6.28 [January 5, 2017]
-  No changes.
-
-Version 1.6.29beta01 [January 12, 2017]
-  Readded "include(GNUInstallDirs)" to CMakeLists.txt (Gianfranco Costamagna).
-  Moved SSE2 optimization code into the main libpng source directory.
-    Configure libpng with "configure --enable-intel-sse" or compile
-    libpng with "-DPNG_INTEL_SSE" in CPPFLAGS to enable it.
-  Simplified conditional compilation in pngvalid.c, for AIX (Michael Felt).
-
-Version 1.6.29beta02 [February 22, 2017]
-  Avoid conditional directives that break statements in pngrutil.c (Romero
-    Malaquias)
-  The contrib/examples/pngtopng.c recovery code was in the wrong "if"
-    branches; the comments were correct.
-  Added code for PowerPC VSX optimisation (Vadim Barkov).
-
-Version 1.6.29beta03 [March 1, 2017]
-  Avoid potential overflow of shift operations in png_do_expand() (Aaron Boxer).
-  Change test ZLIB_VERNUM >= 0x1281 to ZLIB_VERNUM >= 0x1290 in pngrutil.c
-    because Solaris 11 distributes zlib-1.2.8.f that is older than 1.2.8.1,
-    as suggested in zlib FAQ, item 24.
-  Suppress clang warnings about implicit sign changes in png.c
-
-Version 1.6.29 [March 16, 2017]
-  No changes.
-
-Version 1.6.30beta01 [April 1, 2017]
-  Added missing "$(CPPFLAGS)" to the compile line for c.pic.o in
-    makefile.linux and makefile.solaris-x86 (Cosmin).
-  Revised documentation of png_get_error_ptr() in the libpng manual.
-  Silence clang -Wcomma and const drop warnings (Viktor Szakats).
-  Update Sourceforge URLs in documentation (https instead of http).
-
-Version 1.6.30beta02 [April 22, 2017]
-  Document need to check for integer overflow when allocating a pixel
-    buffer for multiple rows in contrib/gregbook, contrib/pngminus,
-    example.c, and in the manual (suggested by Jaeseung Choi). This
-    is similar to the bug reported against pngquant in CVE-2016-5735.
-  Removed reference to the obsolete PNG_SAFE_LIMITS macro in the documentation.
-
-Version 1.6.30beta03 [May 22, 2017]
-  Check for integer overflow in contrib/visupng and contrib/tools/genpng.
-  Do not double evaluate CMAKE_SYSTEM_PROCESSOR in CMakeLists.txt.
-  Test CMAKE_HOST_WIN32 instead of WIN32 in CMakeLists.txt.
-  Fix some URL in documentation.
-
-Version 1.6.30beta04 [June 7, 2017]
-  Avoid writing an empty IDAT when the last IDAT exactly fills the
-    compression buffer (bug report by Brian Baird). This bug was
-    introduced in libpng-1.6.0.
-
-Version 1.6.30rc01 [June 14, 2017]
-  No changes.
-
-Version 1.6.30rc02 [June 25, 2017]
-  Update copyright year in pnglibconf.h, make ltmain.sh executable.
-  Add a reference to the libpng.download site in README.
-
-Version 1.6.30 [June 28, 2017]
-  No changes.
-
-Version 1.6.31beta01 [July 5, 2017]
-  Guard the definition of _POSIX_SOURCE in pngpriv.h (AIX already defines it;
-    bug report by Michael Felt).
-  Revised pngpriv.h to work around failure to compile arm/filter_neon.S
-    ("typedef" directive is unrecognized by the assembler). The problem
-    was introduced in libpng-1.6.30beta01.
-  Added "Requires: zlib" to libpng.pc.in (Pieter Neerincx).
-  Added special case for FreeBSD in arm/filter_neon.S (Maya Rashish).
-
-Version 1.6.31beta02 [July 8, 2017]
-  Added instructions for disabling hardware optimizations in INSTALL.
-  Added "--enable-hardware-optimizations" configuration flag to enable
-    or disable all hardware optimizations with one flag.
-
-Version 1.6.31beta03 [July 9, 2017]
-  Updated CMakeLists.txt to add INTEL_SSE and MIPS_MSA platforms.
-  Changed "int" to "png_size_t" in intel/filter_sse2.c to prevent
-    possible integer overflow (Bug report by John Bowler).
-  Quieted "declaration after statement" warnings in intel/filter_sse2.c.
-  Added scripts/makefile-linux-opt, which has hardware optimizations enabled.
-
-Version 1.6.31beta04 [July 11, 2017]
-  Removed one of the GCC-7.1.0 'strict-overflow' warnings that result when
-    integers appear on both sides of a compare.  Worked around the others by
-    forcing the strict-overflow setting in the relevant functions to a level
-    where they are not reported (John Bowler).
-  Changed "FALL THROUGH" comments to "FALLTHROUGH" because GCC doesn't like
-    the space.
-  Worked around some C-style casts from (void*) because g++ 5.4.0 objects
-    to them.
-  Increased the buffer size for 'sprint' to pass the gcc 7.1.0 'sprint
-    overflow' check that is on by default with -Wall -Wextra.
-
-Version 1.6.31beta05 [July 13, 2017]
-  Added eXIf chunk support.
-
-Version 1.6.31beta06 [July 17, 2017]
-  Added a minimal eXIf chunk (with Orientation and FocalLengthIn35mmFilm
-    tags) to pngtest.png.
-
-Version 1.6.31beta07 [July 18, 2017]
-  Revised the eXIf chunk in pngtest.png to fix "Bad IFD1 Directory" warning.
-
-Version 1.6.31rc01 [July 19, 2017]
-  No changes.
-
-Version 1.6.31rc02 [July 25, 2017]
-  Fixed typo in example.c (png_free_image should be png_image_free) (Bug
-    report by John Smith)
-
-Version 1.6.31 [July 27, 2017]
-  No changes.
-
-Version 1.6.32beta01 [July 31, 2017]
-  Avoid possible NULL dereference in png_handle_eXIf when benign_errors
-    are allowed. Avoid leaking the input buffer "eXIf_buf".
-  Eliminated png_ptr->num_exif member from pngstruct.h and added num_exif
-    to arguments for png_get_eXIf() and png_set_eXIf().
-  Added calls to png_handle_eXIf(() in pngread.c and png_write_eXIf() in
-    pngwrite.c, and made various other fixes to png_write_eXIf().
-  Changed name of png_get_eXIF and png_set_eXIf() to png_get_eXIf_1() and
-    png_set_eXIf_1(), respectively, to avoid breaking API compatibility
-    with libpng-1.6.31.
-
-Version 1.6.32beta02 [August 1, 2017]
-  Updated contrib/libtests/pngunknown.c with eXIf chunk.
-
-Version 1.6.32beta03 [August 2, 2017]
-  Initialized btoa[] in pngstest.c
-  Stop memory leak when returning from png_handle_eXIf() with an error
-    (Bug report from the OSS-fuzz project).
-
-Version 1.6.32beta04 [August 2, 2017]
-  Replaced local eXIf_buf with info_ptr-eXIf_buf in png_handle_eXIf().
-  Update libpng.3 and libpng-manual.txt about eXIf functions.
-
-Version 1.6.32beta05 [August 2, 2017]
-  Restored png_get_eXIf() and png_set_eXIf() to maintain API compatability.
-
-Version 1.6.32beta06 [August 2, 2017]
-  Removed png_get_eXIf_1() and png_set_eXIf_1().
-
-Version 1.6.32beta07 [August 3, 2017]
-  Check length of all chunks except IDAT against user limit to fix an
-    OSS-fuzz issue (Fixes CVE-2017-12652).
-
-Version 1.6.32beta08 [August 3, 2017]
-  Check length of IDAT against maximum possible IDAT size, accounting
-    for height, rowbytes, interlacing and zlib/deflate overhead.
-  Restored png_get_eXIf_1() and png_set_eXIf_1(), because strlen(eXIf_buf)
-    does not work (the eXIf chunk data can contain zeroes).
-
-Version 1.6.32beta09 [August 3, 2017]
-  Require cmake-2.8.8 in CMakeLists.txt. Revised symlink creation,
-    no longer using deprecated cmake LOCATION feature (Clifford Yapp).
-  Fixed five-byte error in the calculation of IDAT maximum possible size.
-  
-Version 1.6.32beta10 [August 5, 2017]
-  Moved chunk-length check into a png_check_chunk_length() private
-    function (Suggested by Max Stepin).
-  Moved bad pngs from tests to contrib/libtests/crashers
-  Moved testing of bad pngs into a separate tests/pngtest-badpngs script
-  Added the --xfail (expected FAIL) option to pngtest.c. It writes XFAIL
-    in the output but PASS for the libpng test.
-  Require cmake-3.0.2 in CMakeLists.txt (Clifford Yapp).
-  Fix "const" declaration info_ptr argument to png_get_eXIf_1() and the
-    num_exif argument to png_get_eXIf_1() (Github Issue 171).
-
-Version 1.6.32beta11 [August 7, 2017]
-  Added "eXIf" to "chunks_to_ignore[]" in png_set_keep_unknown_chunks().
-  Added huge_IDAT.png and empty_ancillary_chunks.png to testpngs/crashers.
-  Make pngtest --strict, --relax, --xfail options imply -m (multiple).
-  Removed unused chunk_name parameter from png_check_chunk_length().
-  Relocated setting free_me for eXIf data, to stop an OSS-fuzz leak.
-  Initialize profile_header[] in png_handle_iCCP() to fix OSS-fuzz issue.
-  Initialize png_ptr->row_buf[0] to 255 in png_read_row() to fix OSS-fuzz UMR.
-  Attempt to fix a UMR in png_set_text_2() to fix OSS-fuzz issue.
-  Increase minimum zlib stream from 9 to 14 in png_handle_iCCP(), to account
-    for the minimum 'deflate' stream, and relocate the test to a point
-    after the keyword has been read.
-  Check that the eXIf chunk has at least 2 bytes and begins with "II" or "MM".
-
-Version 1.6.32rc01 [August 18, 2017]
-  Added a set of "huge_xxxx_chunk.png" files to contrib/testpngs/crashers,
-    one for each known chunk type, with length = 2GB-1.
-  Check for 0 return from png_get_rowbytes() and added some (size_t) typecasts
-    in contrib/pngminus/*.c to stop some Coverity issues (162705, 162706,
-    and 162707).
-  Renamed chunks in contrib/testpngs/crashers to avoid having files whose
-    names differ only in case; this causes problems with some platforms
-    (github issue #172).
-
-Version 1.6.32rc02 [August 22, 2017]
-  Added contrib/oss-fuzz directory which contains files used by the oss-fuzz
-    project (https://github.com/google/oss-fuzz/tree/master/projects/libpng).
-
-Version 1.6.32 [August 24, 2017]
-  No changes.
-
-Version 1.6.33beta01 [August 28, 2017]
-  Added PNGMINUS_UNUSED macro to contrib/pngminus/p*.c and added missing
-    parenthesis in contrib/pngminus/pnm2png.c (bug report by Christian Hesse).
-  Fixed off-by-one error in png_do_check_palette_indexes() (Bug report
-    by Mick P., Source Forge Issue #269).
-
-Version 1.6.33beta02 [September 3, 2017]
-  Initialize png_handler.row_ptr in contrib/oss-fuzz/libpng_read_fuzzer.cc
-    to fix shortlived oss-fuzz issue 3234.
-  Compute a larger limit on IDAT because some applications write a deflate
-    buffer for each row (Bug report by Andrew Church).
-  Use current date (DATE) instead of release-date (RDATE) in last
-    changed date of contrib/oss-fuzz files.
-  Enabled ARM support in CMakeLists.txt (Bernd Kuhls).
-
-Version 1.6.33beta03 [September 14, 2017]
-  Fixed incorrect typecast of some arguments to png_malloc() and
-    png_calloc() that were png_uint_32 instead of png_alloc_size_t
-    (Bug report by "irwir" in Github libpng issue #175).
-  Use pnglibconf.h.prebuilt when building for ANDROID with cmake (Github
-    issue 162, by rcdailey).
-
-Version 1.6.33rc01 [September 20, 2017]
-  Initialize memory allocated by png_inflate to zero, using memset, to
-    stop an oss-fuzz "use of uninitialized value" detection in png_set_text_2()
-    due to truncated iTXt or zTXt chunk.
-  Initialize memory allocated by png_read_buffer to zero, using memset, to
-    stop an oss-fuzz "use of uninitialized value" detection in
-    png_icc_check_tag_table() due to truncated iCCP chunk.
-  Removed a redundant test (suggested by "irwir" in Github issue #180).
-
-Version 1.6.33rc02 [September 23, 2017]
-  Added an interlaced version of each file in contrib/pngsuite.
-  Relocate new memset() call in pngrutil.c.
-  Removed more redundant tests (suggested by "irwir" in Github issue #180).
-  Add support for loading images with associated alpha in the Simplified
-    API (Samuel Williams).
-
-Version 1.6.33 [September 28, 2017]
-  Revert contrib/oss-fuzz/libpng_read_fuzzer.cc to libpng-1.6.32 state.
-  Initialize png_handler.row_ptr in contrib/oss-fuzz/libpng_read_fuzzer.cc
-  Add end_info structure and png_read_end() to the libpng fuzzer.
-
-Version 1.6.34 [September 29, 2017]
-  Removed contrib/pngsuite/i*.png; some of these were incorrect and caused
-    test failures.
-
-Send comments/corrections/commendations to png-mng-implement at lists.sf.net
-(subscription required; visit
-https://lists.sourceforge.net/lists/listinfo/png-mng-implement
-to subscribe)
-or to glennrp at users.sourceforge.net
-
-Glenn R-P
-#endif
diff --git a/libs/freeimage/src/LibPNG/INSTALL b/libs/freeimage/src/LibPNG/INSTALL
deleted file mode 100644
index e8edb7240f..0000000000
--- a/libs/freeimage/src/LibPNG/INSTALL
+++ /dev/null
@@ -1,465 +0,0 @@
-
-    Installing libpng
-
-Contents
-
-       I. Simple installation
-      II. Rebuilding the configure scripts
-     III. Using scripts/makefile*
-      IV. Using cmake
-       V. Directory structure
-      VI. Building with project files
-     VII. Building with makefiles
-    VIII. Configuring libpng for 16-bit platforms
-      IX. Configuring for DOS
-       X. Configuring for Medium Model
-      XI. Prepending a prefix to exported symbols
-     XII. Configuring for compiler xxx:
-    XIII. Removing unwanted object code
-     XIV. Enabling or disabling hardware optimizations
-      XV. Changes to the build and configuration of libpng in libpng-1.5.x
-     XVI. Setjmp/longjmp issues
-    XVII. Common linking failures
-   XVIII. Other sources of information about libpng
-
-I. Simple installation
-
-On Unix/Linux and similar systems, you can simply type
-
-    ./configure [--prefix=/path]
-    make check
-    make install
-
-and ignore the rest of this document.  "/path" is the path to the directory
-where you want to install the libpng "lib", "include", and "bin"
-subdirectories.
-
-If you downloaded a GIT clone, you will need to run ./autogen.sh before
-running ./configure, to create "configure" and "Makefile.in" which are
-not included in the GIT repository.
-
-Note that "configure" is only included in the "*.tar" distributions and not
-in the "*.zip" or "*.7z" distributions. If you downloaded one of those
-distributions, see "Building with project files" or "Building with makefiles",
-below.
-
-II. Rebuilding the configure scripts
-
-If configure does not work on your system, or if you have a need to
-change configure.ac or Makefile.am, and you have a reasonably
-up-to-date set of tools, running ./autogen.sh in a git clone before
-running ./configure may fix the problem.  To be really sure that you
-aren't using any of the included pre-built scripts, especially if you
-are building from a tar distribution instead of a git distribution,
-do this:
-
-    ./configure --enable-maintainer-mode
-    make maintainer-clean
-    ./autogen.sh --maintainer --clean
-    ./autogen.sh --maintainer
-    ./configure [--prefix=/path] [other options]
-    make
-    make install
-    make check
-
-III. Using scripts/makefile*
-
-Instead, you can use one of the custom-built makefiles in the
-"scripts" directory
-
-    cp scripts/pnglibconf.h.prebuilt pnglibconf.h
-    cp scripts/makefile.system makefile
-    make test
-    make install
-
-The files that are presently available in the scripts directory
-are listed and described in scripts/README.txt.
-
-Or you can use one of the "projects" in the "projects" directory.
-
-Before installing libpng, you must first install zlib, if it
-is not already on your system.  zlib can usually be found
-wherever you got libpng; otherwise go to https://zlib.net/.  You can
-place zlib in the same directory as libpng or in another directory.
-
-If your system already has a preinstalled zlib you will still need
-to have access to the zlib.h and zconf.h include files that
-correspond to the version of zlib that's installed.
-
-If you wish to test with a particular zlib that is not first in the
-standard library search path, put ZLIBLIB, ZLIBINC, CPPFLAGS, LDFLAGS,
-and LD_LIBRARY_PATH in your environment before running "make test"
-or "make distcheck":
-
-    ZLIBLIB=/path/to/lib export ZLIBLIB
-    ZLIBINC=/path/to/include export ZLIBINC
-    CPPFLAGS="-I$ZLIBINC" export CPPFLAGS
-    LDFLAGS="-L$ZLIBLIB" export LDFLAGS
-    LD_LIBRARY_PATH="$ZLIBLIB:$LD_LIBRARY_PATH" export LD_LIBRARY_PATH
-
-If you are using one of the makefile scripts, put ZLIBLIB and ZLIBINC
-in your environment and type
-
-    make ZLIBLIB=$ZLIBLIB ZLIBINC=$ZLIBINC test
-
-IV. Using cmake
-
-If you want to use "cmake" (see www.cmake.org), type
-
-    cmake . -DCMAKE_INSTALL_PREFIX=/path
-    make
-    make install
-
-As when using the simple configure method described above, "/path" points to
-the installation directory where you want to put the libpng "lib", "include",
-and "bin" subdirectories.
-
-V. Directory structure
-
-You can rename the directories that you downloaded (they
-might be called "libpng-x.y.z" or "libpngNN" and "zlib-1.2.8"
-or "zlib128") so that you have directories called "zlib" and "libpng".
-
-Your directory structure should look like this:
-
-    .. (the parent directory)
-      libpng (this directory)
-          INSTALL (this file)
-          README
-          *.h, *.c  => libpng source files
-          CMakeLists.txt    =>  "cmake" script
-          configuration files:
-             configure.ac, configure, Makefile.am, Makefile.in,
-             autogen.sh, config.guess, ltmain.sh, missing, libpng.pc.in,
-             libpng-config.in, aclocal.m4, config.h.in, config.sub,
-             depcomp, install-sh, mkinstalldirs, test-pngtest.sh
-          contrib
-             arm-neon, conftest, examples, gregbook, libtests, pngminim,
-             pngminus, pngsuite, tools, visupng
-          projects
-             cbuilder5, owatcom, visualc71, vstudio, xcode
-          scripts
-             makefile.*
-             *.def (module definition files)
-             etc.
-          pngtest.png
-          etc.
-      zlib
-          README, *.h, *.c contrib, etc.
-
-If the line endings in the files look funny, you may wish to get the other
-distribution of libpng.  It is available in both tar.gz (UNIX style line
-endings) and zip (DOS style line endings) formats.
-
-VI. Building with project files
-
-If you are building libpng with MSVC, you can enter the
-libpng projects\visualc71 or vstudio directory and follow the instructions
-in README.txt.
-
-Otherwise enter the zlib directory and follow the instructions in zlib/README,
-then come back here and run "configure" or choose the appropriate
-makefile.sys in the scripts directory.
-
-VII. Building with makefiles
-
-Copy the file (or files) that you need from the
-scripts directory into this directory, for example
-
-MSDOS example:
-
-    copy scripts\makefile.msc makefile
-    copy scripts\pnglibconf.h.prebuilt pnglibconf.h
-
-UNIX example:
-
-    cp scripts/makefile.std makefile
-    cp scripts/pnglibconf.h.prebuilt pnglibconf.h
-
-Read the makefile to see if you need to change any source or
-target directories to match your preferences.
-
-Then read pnglibconf.dfa to see if you want to make any configuration
-changes.
-
-Then just run "make" which will create the libpng library in
-this directory and "make test" which will run a quick test that reads
-the "pngtest.png" file and writes a "pngout.png" file that should be
-identical to it.  Look for "9782 zero samples" in the output of the
-test.  For more confidence, you can run another test by typing
-"pngtest pngnow.png" and looking for "289 zero samples" in the output.
-Also, you can run "pngtest -m contrib/pngsuite/*.png" and compare
-your output with the result shown in contrib/pngsuite/README.
-
-Most of the makefiles will allow you to run "make install" to
-put the library in its final resting place (if you want to
-do that, run "make install" in the zlib directory first if necessary).
-Some also allow you to run "make test-installed" after you have
-run "make install".
-
-VIII. Configuring libpng for 16-bit platforms
-
-You will want to look into zconf.h to tell zlib (and thus libpng) that
-it cannot allocate more than 64K at a time.  Even if you can, the memory
-won't be accessible.  So limit zlib and libpng to 64K by defining MAXSEG_64K.
-
-IX. Configuring for DOS
-
-For DOS users who only have access to the lower 640K, you will
-have to limit zlib's memory usage via a png_set_compression_mem_level()
-call.  See zlib.h or zconf.h in the zlib library for more information.
-
-X. Configuring for Medium Model
-
-Libpng's support for medium model has been tested on most of the popular
-compilers.  Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
-defined, and FAR gets defined to far in pngconf.h, and you should be
-all set.  Everything in the library (except for zlib's structure) is
-expecting far data.  You must use the typedefs with the p or pp on
-the end for pointers (or at least look at them and be careful).  Make
-note that the rows of data are defined as png_bytepp, which is
-an "unsigned char far * far *".
-
-XI. Prepending a prefix to exported symbols
-
-Starting with libpng-1.6.0, you can configure libpng (when using the
-"configure" script) to prefix all exported symbols by means of the
-configuration option "--with-libpng-prefix=FOO_", where FOO_ can be any
-string beginning with a letter and containing only uppercase
-and lowercase letters, digits, and the underscore (i.e., a C language
-identifier).  This creates a set of macros in pnglibconf.h, so this is
-transparent to applications; their function calls get transformed by
-the macros to use the modified names.
-
-XII. Configuring for compiler xxx:
-
-All includes for libpng are in pngconf.h.  If you need to add, change
-or delete an include, this is the place to do it.
-The includes that are not needed outside libpng are placed in pngpriv.h,
-which is only used by the routines inside libpng itself.
-The files in libpng proper only include pngpriv.h and png.h, which
-in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
-As of libpng-1.5.0, pngpriv.h also includes three other private header
-files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
-that previously appeared in the public headers.
-
-XIII. Removing unwanted object code
-
-There are a bunch of #define's in pngconf.h that control what parts of
-libpng are compiled.  All the defines end in _SUPPORTED.  If you are
-never going to use a capability, you can change the #define to #undef
-before recompiling libpng and save yourself code and data space, or
-you can turn off individual capabilities with defines that begin with
-"PNG_NO_".
-
-In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead.
-
-You can also turn all of the transforms and ancillary chunk capabilities
-off en masse with compiler directives that define
-PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
-or all four, along with directives to turn on any of the capabilities that
-you do want.  The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the
-extra transformations but still leave the library fully capable of reading
-and writing PNG files with all known public chunks. Use of the
-PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library
-that is incapable of reading or writing ancillary chunks.  If you are
-not using the progressive reading capability, you can turn that off
-with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING
-capability, which you'll still have).
-
-All the reading and writing specific code are in separate files, so the
-linker should only grab the files it needs.  However, if you want to
-make sure, or if you are building a stand alone library, all the
-reading files start with "pngr" and all the writing files start with "pngw".
-The files that don't match either (like png.c, pngtrans.c, etc.)
-are used for both reading and writing, and always need to be included.
-The progressive reader is in pngpread.c
-
-If you are creating or distributing a dynamically linked library (a .so
-or DLL file), you should not remove or disable any parts of the library,
-as this will cause applications linked with different versions of the
-library to fail if they call functions not available in your library.
-The size of the library itself should not be an issue, because only
-those sections that are actually used will be loaded into memory.
-
-XIV. Enabling or disabling hardware optimizations
-
-Certain hardware capabilites, such as the Intel SSE instructions,
-are normally detected at run time. Enable them with configure options
-such as one of
-
-   --enable-arm-neon=yes
-   --enable-mips-msa=yes
-   --enable-intel-sse=yes
-   --enable-powerpc-vsx=yes
-
-or enable them all at once with
-
-   --enable-hardware-optimizations=yes
-
-or, if you are not using "configure", you can use one
-or more of
-
-   CPPFLAGS += "-DPNG_ARM_NEON"
-   CPPFLAGS += "-DPNG_MIPS_MSA"
-   CPPFLAGS += "-DPNG_INTEL_SSE"
-   CPPFLAGS += "-DPNG_POWERPC_VSX"
-
-See for example scripts/makefile.linux-opt
-
-If you wish to avoid using them,
-you can disable them via the configure option
-
-   --disable-hardware-optimizations
-
-to disable them all, or
-
-   --enable-intel-sse=no
-
-to disable a particular one,
-or via compiler-command options such as
-
-   CPPFLAGS += "-DPNG_ARM_NEON_OPT=0, -DPNG_MIPS_MSA_OPT=0,
-   -DPNG_INTEL_SSE_OPT=0, -DPNG_POWERPC_VSX_OPT=0"
-
-If you are using cmake, hardware optimizations are "on"
-by default. To disable them, use
-
-    cmake . -DPNG_ARM_NEON=no -DPNG_INTEL_SSE=no \
-            -DPNG_MIPS_MSA=no -DPNG_POWERPC_VSX=no
-
-or disable them all at once with
-
-    cmake . -DPNG_HARDWARE_OPTIMIZATIONS=no
-
-XV. Changes to the build and configuration of libpng in libpng-1.5.x
-
-Details of internal changes to the library code can be found in the CHANGES
-file and in the GIT repository logs.  These will be of no concern to the vast
-majority of library users or builders; however, the few who configure libpng
-to a non-default feature set may need to change how this is done.
-
-There should be no need for library builders to alter build scripts if
-these use the distributed build support - configure or the makefiles -
-however, users of the makefiles may care to update their build scripts
-to build pnglibconf.h where the corresponding makefile does not do so.
-
-Building libpng with a non-default configuration has changed completely.
-The old method using pngusr.h should still work correctly even though the
-way pngusr.h is used in the build has been changed; however, library
-builders will probably want to examine the changes to take advantage of
-new capabilities and to simplify their build system.
-
-A. Specific changes to library configuration capabilities
-
-The exact mechanism used to control attributes of API functions has
-changed.  A single set of operating system independent macro definitions
-is used and operating system specific directives are defined in
-pnglibconf.h
-
-As part of this the mechanism used to choose procedure call standards on
-those systems that allow a choice has been changed.  At present this only
-affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
-running on Intel processors.  As before, PNGAPI is defined where required
-to control the exported API functions; however, two new macros, PNGCBAPI
-and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
-(PNGCAPI) for functions that must match a C library prototype (currently
-only png_longjmp_ptr, which must match the C longjmp function.)  The new
-approach is documented in pngconf.h
-
-Despite these changes, libpng 1.5.0 only supports the native C function
-calling standard on those platforms tested so far ("__cdecl" on Microsoft
-Windows).  This is because the support requirements for alternative
-calling conventions seem to no longer exist.  Developers who find it
-necessary to set PNG_API_RULE to 1 should advise the mailing list
-(png-mng-implement) of this and library builders who use Openwatcom and
-therefore set PNG_API_RULE to 2 should also contact the mailing list.
-
-B. Changes to the configuration mechanism
-
-Prior to libpng-1.5.0 library builders who needed to configure libpng
-had either to modify the exported pngconf.h header file to add system
-specific configuration or had to write feature selection macros into
-pngusr.h and cause this to be included into pngconf.h by defining
-PNG_USER_CONFIG. The latter mechanism had the disadvantage that an
-application built without PNG_USER_CONFIG defined would see the
-unmodified, default, libpng API and thus would probably fail to link.
-
-These mechanisms still work in the configure build and in any makefile
-build that builds pnglibconf.h, although the feature selection macros
-have changed somewhat as described above.  In 1.5.0, however, pngusr.h is
-processed only once, at the time the exported header file pnglibconf.h is
-built.  pngconf.h no longer includes pngusr.h; therefore, pngusr.h is ignored
-after the build of pnglibconf.h and it is never included in an application
-build.
-
-The formerly used alternative of adding a list of feature macros to the
-CPPFLAGS setting in the build also still works; however, the macros will be
-copied to pnglibconf.h and this may produce macro redefinition warnings
-when the individual C files are compiled.
-
-All configuration now only works if pnglibconf.h is built from
-scripts/pnglibconf.dfa.  This requires the program awk.  Brian Kernighan
-(the original author of awk) maintains C source code of that awk and this
-and all known later implementations (often called by subtly different
-names - nawk and gawk for example) are adequate to build pnglibconf.h.
-The Sun Microsystems (now Oracle) program 'awk' is an earlier version
-and does not work; this may also apply to other systems that have a
-functioning awk called 'nawk'.
-
-Configuration options are now documented in scripts/pnglibconf.dfa.  This
-file also includes dependency information that ensures a configuration is
-consistent; that is, if a feature is switched off, dependent features are
-also switched off.  As a recommended alternative to using feature macros in
-pngusr.h a system builder may also define equivalent options in pngusr.dfa
-(or, indeed, any file) and add that to the configuration by setting
-DFA_XTRA to the file name.  The makefiles in contrib/pngminim illustrate
-how to do this, and also illustrate a case where pngusr.h is still required.
-
-After you have built libpng, the definitions that were recorded in
-pnglibconf.h are available to your application (pnglibconf.h is included
-in png.h and gets installed alongside png.h and pngconf.h in your
-$PREFIX/include directory).  Do not edit pnglibconf.h after you have built
-libpng, because than the settings would not accurately reflect the settings
-that were used to build libpng.
-
-XVI. Setjmp/longjmp issues
-
-Libpng uses setjmp()/longjmp() for error handling.  Unfortunately setjmp()
-is known to be not thread-safe on some platforms and we don't know of
-any platform where it is guaranteed to be thread-safe.  Therefore, if
-your application is going to be using multiple threads, you should
-configure libpng with PNG_NO_SETJMP in your pngusr.dfa file, with
--DPNG_NO_SETJMP on your compile line, or with
-
-    #undef PNG_SETJMP_SUPPORTED
-
-in your pnglibconf.h or pngusr.h.
-
-Starting with libpng-1.6.0, the library included a "simplified API".
-This requires setjmp/longjmp, so you must either build the library
-with PNG_SETJMP_SUPPORTED defined, or with PNG_SIMPLIFIED_READ_SUPPORTED
-and PNG_SIMPLIFIED_WRITE_SUPPORTED undefined.
-
-XVII. Common linking failures
-
-If your application fails to find libpng or zlib entries while linking:
-
-  Be sure "-lz" appears after "-lpng" on your linking command.
-
-  Be sure you have built libpng, zlib, and your application for the
-  same platform (e.g., 32-bit or 64-bit).
-
-  If you are using the vstudio project, observe the WARNING in
-  project/vstudio/README.txt.
-
-XVIII. Other sources of information about libpng:
-
-Further information can be found in the README and libpng-manual.txt
-files, in the individual makefiles, in png.h, and the manual pages
-libpng.3 and png.5.
-
-Copyright (c) 1998-2002,2006-2016 Glenn Randers-Pehrson
-This document is released under the libpng license.
-For conditions of distribution and use, see the disclaimer
-and license in png.h.
diff --git a/libs/freeimage/src/LibPNG/README b/libs/freeimage/src/LibPNG/README
deleted file mode 100644
index 0da5a5ef83..0000000000
--- a/libs/freeimage/src/LibPNG/README
+++ /dev/null
@@ -1,222 +0,0 @@
-README for libpng version 1.6.34 - September 29, 2017 (shared library 16.0)
-See the note about version numbers near the top of png.h
-
-See INSTALL for instructions on how to install libpng.
-
-Libpng comes in several distribution formats.  Get libpng-*.tar.gz or
-libpng-*.tar.xz or if you want UNIX-style line endings in the text files,
-or lpng*.7z or lpng*.zip if you want DOS-style line endings.
-
-Version 0.89 was the first official release of libpng.  Don't let the
-fact that it's the first release fool you.  The libpng library has been in
-extensive use and testing since mid-1995.  By late 1997 it had
-finally gotten to the stage where there hadn't been significant
-changes to the API in some time, and people have a bad feeling about
-libraries with versions < 1.0.  Version 1.0.0 was released in
-March 1998.
-
-****
-Note that some of the changes to the png_info structure render this
-version of the library binary incompatible with libpng-0.89 or
-earlier versions if you are using a shared library.  The type of the
-"filler" parameter for png_set_filler() has changed from png_byte to
-png_uint_32, which will affect shared-library applications that use
-this function.
-
-To avoid problems with changes to the internals of the png info_struct,
-new APIs have been made available in 0.95 to avoid direct application
-access to info_ptr.  These functions are the png_set_<chunk> and
-png_get_<chunk> functions.  These functions should be used when
-accessing/storing the info_struct data, rather than manipulating it
-directly, to avoid such problems in the future.
-
-It is important to note that the APIs did not make current programs
-that access the info struct directly incompatible with the new
-library, through libpng-1.2.x.  In libpng-1.4.x, which was meant to
-be a transitional release, members of the png_struct and the
-info_struct can still be accessed, but the compiler will issue a
-warning about deprecated usage.  Since libpng-1.5.0, direct access
-to these structs is not allowed, and the definitions of the structs
-reside in private pngstruct.h and pnginfo.h header files that are not
-accessible to applications.  It is strongly suggested that new
-programs use the new APIs (as shown in example.c and pngtest.c), and
-older programs be converted to the new format, to facilitate upgrades
-in the future.
-****
-
-Additions since 0.90 include the ability to compile libpng as a
-Windows DLL, and new APIs for accessing data in the info struct.
-Experimental functions include the ability to set weighting and cost
-factors for row filter selection, direct reads of integers from buffers
-on big-endian processors that support misaligned data access, faster
-methods of doing alpha composition, and more accurate 16->8 bit color
-conversion.
-
-The additions since 0.89 include the ability to read from a PNG stream
-which has had some (or all) of the signature bytes read by the calling
-application.  This also allows the reading of embedded PNG streams that
-do not have the PNG file signature.  As well, it is now possible to set
-the library action on the detection of chunk CRC errors.  It is possible
-to set different actions based on whether the CRC error occurred in a
-critical or an ancillary chunk.
-
-The changes made to the library, and bugs fixed are based on discussions
-on the PNG-implement mailing list and not on material submitted
-privately to Guy, Andreas, or Glenn.  They will forward any good
-suggestions to the list.
-
-For a detailed description on using libpng, read libpng-manual.txt.  For
-examples of libpng in a program, see example.c and pngtest.c.  For usage
-information and restrictions (what little they are) on libpng, see
-png.h.  For a description on using zlib (the compression library used by
-libpng) and zlib's restrictions, see zlib.h
-
-I have included a general makefile, as well as several machine and
-compiler specific ones, but you may have to modify one for your own needs.
-
-You should use zlib 1.0.4 or later to run this, but it MAY work with
-versions as old as zlib 0.95.  Even so, there are bugs in older zlib
-versions which can cause the output of invalid compression streams for
-some images.  You will definitely need zlib 1.0.4 or later if you are
-taking advantage of the MS-DOS "far" structure allocation for the small
-and medium memory models.  You should also note that zlib is a
-compression library that is useful for more things than just PNG files.
-You can use zlib as a drop-in replacement for fread() and fwrite() if
-you are so inclined.
-
-zlib should be available at the same place that libpng is, or at zlib.net.
-
-You may also want a copy of the PNG specification.  It is available
-as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find
-these at http://www.libpng.org/pub/png/pngdocs.html .
-
-This code is currently being archived at libpng.sourceforge.io in the
-[DOWNLOAD] area, and at http://libpng.download/src .  If you
-can't find it in any of those places, e-mail me, and I'll help you find it.
-
-I am not a lawyer, but I believe that the Export Control Classification
-Number (ECCN) for libpng is EAR99, which means not subject to export
-controls or International Traffic in Arms Regulations (ITAR) because it
-is open source, publicly available software, that does not contain any
-encryption software.  See the EAR, paragraphs 734.3(b)(3) and 734.7(b).
-
-If you have any code changes, requests, problems, etc., please e-mail
-them to me.  Also, I'd appreciate any make files or project files,
-and any modifications you needed to make to get libpng to compile,
-along with a #define variable to tell what compiler/system you are on.
-If you needed to add transformations to libpng, or wish libpng would
-provide the image in a different way, drop me a note (and code, if
-possible), so I can consider supporting the transformation.
-Finally, if you get any warning messages when compiling libpng
-(note: not zlib), and they are easy to fix, I'd appreciate the
-fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
-
-This release was created and will be supported by myself (of course
-based in a large way on Guy's and Andreas' earlier work), and the PNG
-development group.
-
-Send comments/corrections/commendations to png-mng-implement at
-lists.sourceforge.net (subscription required; visit
-https://lists.sourceforge.net/lists/listinfo/png-mng-implement
-to subscribe) or to glennrp at users.sourceforge.net
-
-You can't reach Guy, the original libpng author, at the addresses
-given in previous versions of this document.  He and Andreas will
-read mail addressed to the png-implement list, however.
-
-Please do not send general questions about PNG.  Send them to
-png-mng-misc at lists.sf.net (subscription required; visit
-https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
-subscribe).  If you have a question about something
-in the PNG specification that is related to using libpng, send it
-to me.  Send me any questions that start with "I was using libpng,
-and ...".  If in doubt, send questions to me.  I'll bounce them
-to others, if necessary.
-
-Please do not send suggestions on how to change PNG.  We have
-been discussing PNG for twenty years now, and it is official and
-finished.  If you have suggestions for libpng, however, I'll
-gladly listen.  Even if your suggestion is not used immediately,
-it may be used later.
-
-Files in this distribution:
-
-      ANNOUNCE      =>  Announcement of this version, with recent changes
-      CHANGES       =>  Description of changes between libpng versions
-      KNOWNBUG      =>  List of known bugs and deficiencies
-      LICENSE       =>  License to use and redistribute libpng
-      README        =>  This file
-      TODO          =>  Things not implemented in the current library
-      Y2KINFO       =>  Statement of Y2K compliance
-      example.c     =>  Example code for using libpng functions
-      libpng.3      =>  manual page for libpng (includes libpng-manual.txt)
-      libpng-manual.txt  =>  Description of libpng and its functions
-      libpngpf.3    =>  manual page for libpng's private functions
-      png.5         =>  manual page for the PNG format
-      png.c         =>  Basic interface functions common to library
-      png.h         =>  Library function and interface declarations (public)
-      pngpriv.h     =>  Library function and interface declarations (private)
-      pngconf.h     =>  System specific library configuration (public)
-      pngstruct.h   =>  png_struct declaration (private)
-      pnginfo.h     =>  png_info struct declaration (private)
-      pngdebug.h    =>  debugging macros (private)
-      pngerror.c    =>  Error/warning message I/O functions
-      pngget.c      =>  Functions for retrieving info from struct
-      pngmem.c      =>  Memory handling functions
-      pngbar.png    =>  PNG logo, 88x31
-      pngnow.png    =>  PNG logo, 98x31
-      pngpread.c    =>  Progressive reading functions
-      pngread.c     =>  Read data/helper high-level functions
-      pngrio.c      =>  Lowest-level data read I/O functions
-      pngrtran.c    =>  Read data transformation functions
-      pngrutil.c    =>  Read data utility functions
-      pngset.c      =>  Functions for storing data into the info_struct
-      pngtest.c     =>  Library test program
-      pngtest.png   =>  Library test sample image
-      pngtrans.c    =>  Common data transformation functions
-      pngwio.c      =>  Lowest-level write I/O functions
-      pngwrite.c    =>  High-level write functions
-      pngwtran.c    =>  Write data transformations
-      pngwutil.c    =>  Write utility functions
-      arm           =>  Contains optimized code for the ARM platform
-      powerpc       =>  Contains optimized code for the PowerPC platform
-      contrib       =>  Contributions
-       arm-neon         =>  Optimized code for ARM-NEON platform
-       powerpc-vsx      =>  Optimized code for POWERPC-VSX platform
-       examples         =>  Example programs
-       gregbook         =>  source code for PNG reading and writing, from
-                            Greg Roelofs' "PNG: The Definitive Guide",
-                            O'Reilly, 1999
-       libtests         =>  Test programs
-       mips-msa         =>  Optimized code for MIPS-MSA platform
-       pngminim         =>  Minimal decoder, encoder, and progressive decoder
-                            programs demonstrating use of pngusr.dfa
-       pngminus         =>  Simple pnm2png and png2pnm programs
-       pngsuite         =>  Test images
-       testpngs
-       tools            =>  Various tools
-       visupng          =>  Contains a MSVC workspace for VisualPng
-      intel             =>  Optimized code for INTEL-SSE2 platform
-      mips              =>  Optimized code for MIPS platform
-      projects      =>  Contains project files and workspaces for
-                        building a DLL
-       owatcom          =>  Contains a WATCOM project for building libpng
-       visualc71        =>  Contains a Microsoft Visual C++ (MSVC)
-                            workspace for building libpng and zlib
-       vstudio          =>  Contains a Microsoft Visual C++ (MSVC)
-                            workspace for building libpng and zlib
-      scripts       =>  Directory containing scripts for building libpng:
-                            (see scripts/README.txt for the list of scripts)
-
-Good luck, and happy coding.
-
--Glenn Randers-Pehrson (current maintainer, since 1998)
- Internet: glennrp at users.sourceforge.net
-
--Andreas Eric Dilger (former maintainer, 1996-1997)
- Internet: adilger at enel.ucalgary.ca
- Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
-
--Guy Eric Schalnat (original author and former maintainer, 1995-1996)
- (formerly of Group 42, Inc)
- Internet: gschal at infinet.com
diff --git a/libs/freeimage/src/LibPNG/TODO b/libs/freeimage/src/LibPNG/TODO
deleted file mode 100644
index 36d6092a2e..0000000000
--- a/libs/freeimage/src/LibPNG/TODO
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
-TODO - list of things to do for libpng:
-
-Final bug fixes.
-Better C++ wrapper/full C++ implementation?
-Fix problem with C++ and EXTERN "C".
-cHRM transformation.
-Remove setjmp/longjmp usage in favor of returning error codes. As a start on
-  this, minimize the use of png_error(), replacing them with
-  png_warning(); return(0); or similar.
-Palette creation.
-Add "grayscale->palette" transformation and "palette->grayscale" detection.
-Improved dithering.
-Multi-lingual error and warning message support.
-Complete sRGB transformation (presently it simply uses gamma=0.45455).
-Man pages for function calls.
-Better documentation.
-Better filter selection
-   (counting huffman bits/precompression?  filter inertia?  filter costs?).
-Histogram creation.
-Text conversion between different code pages (Latin-1 -> Mac and DOS).
-Avoid building gamma tables whenever possible.
-Use greater precision when changing to linear gamma for compositing against
-  background and doing rgb-to-gray transformation.
-Investigate pre-incremented loop counters and other loop constructions.
-Add interpolated method of handling interlacing.
-Extend pngvalid.c to validate more of the libpng transformations.
-Refactor preprocessor conditionals to compile entire statements
-
-*/
diff --git a/libs/freeimage/src/LibPNG/libpng-manual.txt b/libs/freeimage/src/LibPNG/libpng-manual.txt
deleted file mode 100644
index d4407ef2ea..0000000000
--- a/libs/freeimage/src/LibPNG/libpng-manual.txt
+++ /dev/null
@@ -1,5464 +0,0 @@
-libpng-manual.txt - A description on how to use and modify libpng
-
- libpng version 1.6.34 - September 29, 2017
- Updated and distributed by Glenn Randers-Pehrson
- <glennrp at users.sourceforge.net>
- Copyright (c) 1998-2017 Glenn Randers-Pehrson
-
- This document is released under the libpng license.
- For conditions of distribution and use, see the disclaimer
- and license in png.h
-
- Based on:
-
- libpng versions 0.97, January 1998, through 1.6.34 - September 29, 2017
- Updated and distributed by Glenn Randers-Pehrson
- Copyright (c) 1998-2017 Glenn Randers-Pehrson
-
- libpng 1.0 beta 6 - version 0.96 - May 28, 1997
- Updated and distributed by Andreas Dilger
- Copyright (c) 1996, 1997 Andreas Dilger
-
- libpng 1.0 beta 2 - version 0.88 - January 26, 1996
- For conditions of distribution and use, see copyright
- notice in png.h. Copyright (c) 1995, 1996 Guy Eric
- Schalnat, Group 42, Inc.
-
- Updated/rewritten per request in the libpng FAQ
- Copyright (c) 1995, 1996 Frank J. T. Wojcik
- December 18, 1995 & January 20, 1996
-
- TABLE OF CONTENTS
-
-    I. Introduction
-   II. Structures
-  III. Reading
-   IV. Writing
-    V. Simplified API
-   VI. Modifying/Customizing libpng
-  VII. MNG support
- VIII. Changes to Libpng from version 0.88
-   IX. Changes to Libpng from version 1.0.x to 1.2.x
-    X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
-   XI. Changes to Libpng from version 1.4.x to 1.5.x
-  XII. Changes to Libpng from version 1.5.x to 1.6.x
- XIII. Detecting libpng
-  XIV. Source code repository
-   XV. Coding style
-  XVI. Y2K Compliance in libpng
-
-I. Introduction
-
-This file describes how to use and modify the PNG reference library
-(known as libpng) for your own use.  In addition to this
-file, example.c is a good starting point for using the library, as
-it is heavily commented and should include everything most people
-will need.  We assume that libpng is already installed; see the
-INSTALL file for instructions on how to configure and install libpng.
-
-For examples of libpng usage, see the files "example.c", "pngtest.c",
-and the files in the "contrib" directory, all of which are included in
-the libpng distribution.
-
-Libpng was written as a companion to the PNG specification, as a way
-of reducing the amount of time and effort it takes to support the PNG
-file format in application programs.
-
-The PNG specification (second edition), November 2003, is available as
-a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2004 (E)) at
-<https://www.w3.org/TR/2003/REC-PNG-20031110/
-The W3C and ISO documents have identical technical content.
-
-The PNG-1.2 specification is available at
-<https://png-mng.sourceforge.io/pub/png/spec/1.2/>.
-It is technically equivalent
-to the PNG specification (second edition) but has some additional material.
-
-The PNG-1.0 specification is available as RFC 2083
-<https://png-mng.sourceforge.io/pub/png/spec/1.0/> and as a
-W3C Recommendation <https://www.w3.org/TR/REC-png-961001>.
-
-Some additional chunks are described in the special-purpose public chunks
-documents at <http://www.libpng.org/pub/png/spec/register/>
-
-Other information
-about PNG, and the latest version of libpng, can be found at the PNG home
-page, <http://www.libpng.org/pub/png/>.
-
-Most users will not have to modify the library significantly; advanced
-users may want to modify it more.  All attempts were made to make it as
-complete as possible, while keeping the code easy to understand.
-Currently, this library only supports C.  Support for other languages
-is being considered.
-
-Libpng has been designed to handle multiple sessions at one time,
-to be easily modifiable, to be portable to the vast majority of
-machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
-to use.  The ultimate goal of libpng is to promote the acceptance of
-the PNG file format in whatever way possible.  While there is still
-work to be done (see the TODO file), libpng should cover the
-majority of the needs of its users.
-
-Libpng uses zlib for its compression and decompression of PNG files.
-Further information about zlib, and the latest version of zlib, can
-be found at the zlib home page, <https://zlib.net/>.
-The zlib compression utility is a general purpose utility that is
-useful for more than PNG files, and can be used without libpng.
-See the documentation delivered with zlib for more details.
-You can usually find the source files for the zlib utility wherever you
-find the libpng source files.
-
-Libpng is thread safe, provided the threads are using different
-instances of the structures.  Each thread should have its own
-png_struct and png_info instances, and thus its own image.
-Libpng does not protect itself against two threads using the
-same instance of a structure.
-
-II. Structures
-
-There are two main structures that are important to libpng, png_struct
-and png_info.  Both are internal structures that are no longer exposed
-in the libpng interface (as of libpng 1.5.0).
-
-The png_info structure is designed to provide information about the
-PNG file.  At one time, the fields of png_info were intended to be
-directly accessible to the user.  However, this tended to cause problems
-with applications using dynamically loaded libraries, and as a result
-a set of interface functions for png_info (the png_get_*() and png_set_*()
-functions) was developed, and direct access to the png_info fields was
-deprecated..
-
-The png_struct structure is the object used by the library to decode a
-single image.  As of 1.5.0 this structure is also not exposed.
-
-Almost all libpng APIs require a pointer to a png_struct as the first argument.
-Many (in particular the png_set and png_get APIs) also require a pointer
-to png_info as the second argument.  Some application visible macros
-defined in png.h designed for basic data access (reading and writing
-integers in the PNG format) don't take a png_info pointer, but it's almost
-always safe to assume that a (png_struct*) has to be passed to call an API
-function.
-
-You can have more than one png_info structure associated with an image,
-as illustrated in pngtest.c, one for information valid prior to the
-IDAT chunks and another (called "end_info" below) for things after them.
-
-The png.h header file is an invaluable reference for programming with libpng.
-And while I'm on the topic, make sure you include the libpng header file:
-
-#include <png.h>
-
-and also (as of libpng-1.5.0) the zlib header file, if you need it:
-
-#include <zlib.h>
-
-Types
-
-The png.h header file defines a number of integral types used by the
-APIs.  Most of these are fairly obvious; for example types corresponding
-to integers of particular sizes and types for passing color values.
-
-One exception is how non-integral numbers are handled.  For application
-convenience most APIs that take such numbers have C (double) arguments;
-however, internally PNG, and libpng, use 32 bit signed integers and encode
-the value by multiplying by 100,000.  As of libpng 1.5.0 a convenience
-macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
-which is simply (png_int_32).
-
-All APIs that take (double) arguments also have a matching API that
-takes the corresponding fixed point integer arguments.  The fixed point
-API has the same name as the floating point one with "_fixed" appended.
-The actual range of values permitted in the APIs is frequently less than
-the full range of (png_fixed_point) (-21474 to +21474).  When APIs require
-a non-negative argument the type is recorded as png_uint_32 above.  Consult
-the header file and the text below for more information.
-
-Special care must be take with sCAL chunk handling because the chunk itself
-uses non-integral values encoded as strings containing decimal floating point
-numbers.  See the comments in the header file.
-
-Configuration
-
-The main header file function declarations are frequently protected by C
-preprocessing directives of the form:
-
-    #ifdef PNG_feature_SUPPORTED
-    declare-function
-    #endif
-    ...
-    #ifdef PNG_feature_SUPPORTED
-    use-function
-    #endif
-
-The library can be built without support for these APIs, although a
-standard build will have all implemented APIs.  Application programs
-should check the feature macros before using an API for maximum
-portability.  From libpng 1.5.0 the feature macros set during the build
-of libpng are recorded in the header file "pnglibconf.h" and this file
-is always included by png.h.
-
-If you don't need to change the library configuration from the default, skip to
-the next section ("Reading").
-
-Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
-of the build project files in the 'projects' directory simply copy
-scripts/pnglibconf.h.prebuilt to pnglibconf.h.  This means that these build
-systems do not permit easy auto-configuration of the library - they only
-support the default configuration.
-
-The easiest way to make minor changes to the libpng configuration when
-auto-configuration is supported is to add definitions to the command line
-using (typically) CPPFLAGS.  For example:
-
-CPPFLAGS=-DPNG_NO_FLOATING_ARITHMETIC
-
-will change the internal libpng math implementation for gamma correction and
-other arithmetic calculations to fixed point, avoiding the need for fast
-floating point support.  The result can be seen in the generated pnglibconf.h -
-make sure it contains the changed feature macro setting.
-
-If you need to make more extensive configuration changes - more than one or two
-feature macro settings - you can either add -DPNG_USER_CONFIG to the build
-command line and put a list of feature macro settings in pngusr.h or you can set
-DFA_XTRA (a makefile variable) to a file containing the same information in the
-form of 'option' settings.
-
-A. Changing pnglibconf.h
-
-A variety of methods exist to build libpng.  Not all of these support
-reconfiguration of pnglibconf.h.  To reconfigure pnglibconf.h it must either be
-rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
-
-Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
-pnglibconf.h and changing the lines defining the supported features, paying
-very close attention to the 'option' information in scripts/pnglibconf.dfa
-that describes those features and their requirements.  This is easy to get
-wrong.
-
-B. Configuration using DFA_XTRA
-
-Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
-variant such as 'nawk' or 'gawk', is available.  The configure build will
-automatically find an appropriate awk and build pnglibconf.h.
-The scripts/pnglibconf.mak file contains a set of make rules for doing the
-same thing if configure is not used, and many of the makefiles in the scripts
-directory use this approach.
-
-When rebuilding simply write a new file containing changed options and set
-DFA_XTRA to the name of this file.  This causes the build to append the new file
-to the end of scripts/pnglibconf.dfa.  The pngusr.dfa file should contain lines
-of the following forms:
-
-everything = off
-
-This turns all optional features off.  Include it at the start of pngusr.dfa to
-make it easier to build a minimal configuration.  You will need to turn at least
-some features on afterward to enable either reading or writing code, or both.
-
-option feature on
-option feature off
-
-Enable or disable a single feature.  This will automatically enable other
-features required by a feature that is turned on or disable other features that
-require a feature which is turned off.  Conflicting settings will cause an error
-message to be emitted by awk.
-
-setting feature default value
-
-Changes the default value of setting 'feature' to 'value'.  There are a small
-number of settings listed at the top of pnglibconf.h, they are documented in the
-source code.  Most of these values have performance implications for the library
-but most of them have no visible effect on the API.  Some can also be overridden
-from the API.
-
-This method of building a customized pnglibconf.h is illustrated in
-contrib/pngminim/*.  See the "$(PNGCONF):" target in the makefile and
-pngusr.dfa in these directories.
-
-C. Configuration using PNG_USER_CONFIG
-
-If -DPNG_USER_CONFIG is added to the CPPFLAGS when pnglibconf.h is built,
-the file pngusr.h will automatically be included before the options in
-scripts/pnglibconf.dfa are processed.  Your pngusr.h file should contain only
-macro definitions turning features on or off or setting settings.
-
-Apart from the global setting "everything = off" all the options listed above
-can be set using macros in pngusr.h:
-
-#define PNG_feature_SUPPORTED
-
-is equivalent to:
-
-option feature on
-
-#define PNG_NO_feature
-
-is equivalent to:
-
-option feature off
-
-#define PNG_feature value
-
-is equivalent to:
-
-setting feature default value
-
-Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the
-pngusr file you supply override the contents of scripts/pnglibconf.dfa
-
-If confusing or incomprehensible behavior results it is possible to
-examine the intermediate file pnglibconf.dfn to find the full set of
-dependency information for each setting and option.  Simply locate the
-feature in the file and read the C comments that precede it.
-
-This method is also illustrated in the contrib/pngminim/* makefiles and
-pngusr.h.
-
-III. Reading
-
-We'll now walk you through the possible functions to call when reading
-in a PNG file sequentially, briefly explaining the syntax and purpose
-of each one.  See example.c and png.h for more detail.  While
-progressive reading is covered in the next section, you will still
-need some of the functions discussed in this section to read a PNG
-file.
-
-Setup
-
-You will want to do the I/O initialization(*) before you get into libpng,
-so if it doesn't work, you don't have much to undo.  Of course, you
-will also want to insure that you are, in fact, dealing with a PNG
-file.  Libpng provides a simple check to see if a file is a PNG file.
-To use it, pass in the first 1 to 8 bytes of the file to the function
-png_sig_cmp(), and it will return 0 (false) if the bytes match the
-corresponding bytes of the PNG signature, or nonzero (true) otherwise.
-Of course, the more bytes you pass in, the greater the accuracy of the
-prediction.
-
-If you are intending to keep the file pointer open for use in libpng,
-you must ensure you don't read more than 8 bytes from the beginning
-of the file, and you also have to make a call to png_set_sig_bytes()
-with the number of bytes you read from the beginning.  Libpng will
-then only check the bytes (if any) that your program didn't read.
-
-(*): If you are not using the standard I/O functions, you will need
-to replace them with custom functions.  See the discussion under
-Customizing libpng.
-
-    FILE *fp = fopen(file_name, "rb");
-    if (!fp)
-    {
-       return (ERROR);
-    }
-
-    if (fread(header, 1, number, fp) != number)
-    {
-       return (ERROR);
-    }
-
-    is_png = !png_sig_cmp(header, 0, number);
-    if (!is_png)
-    {
-       return (NOT_PNG);
-    }
-
-Next, png_struct and png_info need to be allocated and initialized.  In
-order to ensure that the size of these structures is correct even with a
-dynamically linked libpng, there are functions to initialize and
-allocate the structures.  We also pass the library version, optional
-pointers to error handling functions, and a pointer to a data struct for
-use by the error functions, if necessary (the pointer and functions can
-be NULL if the default error handlers are to be used).  See the section
-on Changes to Libpng below regarding the old initialization functions.
-The structure allocation functions quietly return NULL if they fail to
-create the structure, so your application should check for that.
-
-    png_structp png_ptr = png_create_read_struct
-        (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
-        user_error_fn, user_warning_fn);
-
-    if (!png_ptr)
-       return (ERROR);
-
-    png_infop info_ptr = png_create_info_struct(png_ptr);
-
-    if (!info_ptr)
-    {
-       png_destroy_read_struct(&png_ptr,
-           (png_infopp)NULL, (png_infopp)NULL);
-       return (ERROR);
-    }
-
-If you want to use your own memory allocation routines,
-use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use
-png_create_read_struct_2() instead of png_create_read_struct():
-
-    png_structp png_ptr = png_create_read_struct_2
-        (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
-        user_error_fn, user_warning_fn, (png_voidp)
-        user_mem_ptr, user_malloc_fn, user_free_fn);
-
-The error handling routines passed to png_create_read_struct()
-and the memory alloc/free routines passed to png_create_struct_2()
-are only necessary if you are not using the libpng supplied error
-handling and memory alloc/free functions.
-
-When libpng encounters an error, it expects to longjmp back
-to your routine.  Therefore, you will need to call setjmp and pass
-your png_jmpbuf(png_ptr).  If you read the file from different
-routines, you will need to update the longjmp buffer every time you enter
-a new routine that will call a png_*() function.
-
-See your documentation of setjmp/longjmp for your compiler for more
-information on setjmp/longjmp.  See the discussion on libpng error
-handling in the Customizing Libpng section below for more information
-on the libpng error handling.  If an error occurs, and libpng longjmp's
-back to your setjmp, you will want to call png_destroy_read_struct() to
-free any memory.
-
-    if (setjmp(png_jmpbuf(png_ptr)))
-    {
-       png_destroy_read_struct(&png_ptr, &info_ptr,
-           &end_info);
-       fclose(fp);
-       return (ERROR);
-    }
-
-Pass (png_infopp)NULL instead of &end_info if you didn't create
-an end_info structure.
-
-If you would rather avoid the complexity of setjmp/longjmp issues,
-you can compile libpng with PNG_NO_SETJMP, in which case
-errors will result in a call to PNG_ABORT() which defaults to abort().
-
-You can #define PNG_ABORT() to a function that does something
-more useful than abort(), as long as your function does not
-return.
-
-Now you need to set up the input code.  The default for libpng is to
-use the C function fread().  If you use this, you will need to pass a
-valid FILE * in the function png_init_io().  Be sure that the file is
-opened in binary mode.  If you wish to handle reading data in another
-way, you need not call the png_init_io() function, but you must then
-implement the libpng I/O methods discussed in the Customizing Libpng
-section below.
-
-    png_init_io(png_ptr, fp);
-
-If you had previously opened the file and read any of the signature from
-the beginning in order to see if this was a PNG file, you need to let
-libpng know that there are some bytes missing from the start of the file.
-
-    png_set_sig_bytes(png_ptr, number);
-
-You can change the zlib compression buffer size to be used while
-reading compressed data with
-
-    png_set_compression_buffer_size(png_ptr, buffer_size);
-
-where the default size is 8192 bytes.  Note that the buffer size
-is changed immediately and the buffer is reallocated immediately,
-instead of setting a flag to be acted upon later.
-
-If you want CRC errors to be handled in a different manner than
-the default, use
-
-    png_set_crc_action(png_ptr, crit_action, ancil_action);
-
-The values for png_set_crc_action() say how libpng is to handle CRC errors in
-ancillary and critical chunks, and whether to use the data contained
-therein. Starting with libpng-1.6.26, this also governs how an ADLER32 error
-is handled while reading the IDAT chunk. Note that it is impossible to
-"discard" data in a critical chunk.
-
-Choices for (int) crit_action are
-   PNG_CRC_DEFAULT      0  error/quit
-   PNG_CRC_ERROR_QUIT   1  error/quit
-   PNG_CRC_WARN_USE     3  warn/use data
-   PNG_CRC_QUIET_USE    4  quiet/use data
-   PNG_CRC_NO_CHANGE    5  use the current value
-
-Choices for (int) ancil_action are
-   PNG_CRC_DEFAULT      0  error/quit
-   PNG_CRC_ERROR_QUIT   1  error/quit
-   PNG_CRC_WARN_DISCARD 2  warn/discard data
-   PNG_CRC_WARN_USE     3  warn/use data
-   PNG_CRC_QUIET_USE    4  quiet/use data
-   PNG_CRC_NO_CHANGE    5  use the current value
-
-When the setting for crit_action is PNG_CRC_QUIET_USE, the CRC and ADLER32
-checksums are not only ignored, but they are not evaluated.
-
-Setting up callback code
-
-You can set up a callback function to handle any unknown chunks in the
-input stream. You must supply the function
-
-    read_chunk_callback(png_structp png_ptr,
-         png_unknown_chunkp chunk);
-    {
-       /* The unknown chunk structure contains your
-          chunk data, along with similar data for any other
-          unknown chunks: */
-
-           png_byte name[5];
-           png_byte *data;
-           png_size_t size;
-
-       /* Note that libpng has already taken care of
-          the CRC handling */
-
-       /* put your code here.  Search for your chunk in the
-          unknown chunk structure, process it, and return one
-          of the following: */
-
-       return (-n); /* chunk had an error */
-       return (0); /* did not recognize */
-       return (n); /* success */
-    }
-
-(You can give your function another name that you like instead of
-"read_chunk_callback")
-
-To inform libpng about your function, use
-
-    png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
-        read_chunk_callback);
-
-This names not only the callback function, but also a user pointer that
-you can retrieve with
-
-    png_get_user_chunk_ptr(png_ptr);
-
-If you call the png_set_read_user_chunk_fn() function, then all unknown
-chunks which the callback does not handle will be saved when read.  You can
-cause them to be discarded by returning '1' ("handled") instead of '0'.  This
-behavior will change in libpng 1.7 and the default handling set by the
-png_set_keep_unknown_chunks() function, described below, will be used when the
-callback returns 0.  If you want the existing behavior you should set the global
-default to PNG_HANDLE_CHUNK_IF_SAFE now; this is compatible with all current
-versions of libpng and with 1.7.  Libpng 1.6 issues a warning if you keep the
-default, or PNG_HANDLE_CHUNK_NEVER, and the callback returns 0.
-
-At this point, you can set up a callback function that will be
-called after each row has been read, which you can use to control
-a progress meter or the like.  It's demonstrated in pngtest.c.
-You must supply a function
-
-    void read_row_callback(png_structp png_ptr,
-       png_uint_32 row, int pass);
-    {
-      /* put your code here */
-    }
-
-(You can give it another name that you like instead of "read_row_callback")
-
-To inform libpng about your function, use
-
-    png_set_read_status_fn(png_ptr, read_row_callback);
-
-When this function is called the row has already been completely processed and
-the 'row' and 'pass' refer to the next row to be handled.  For the
-non-interlaced case the row that was just handled is simply one less than the
-passed in row number, and pass will always be 0.  For the interlaced case the
-same applies unless the row value is 0, in which case the row just handled was
-the last one from one of the preceding passes.  Because interlacing may skip a
-pass you cannot be sure that the preceding pass is just 'pass-1'; if you really
-need to know what the last pass is record (row,pass) from the callback and use
-the last recorded value each time.
-
-As with the user transform you can find the output row using the
-PNG_ROW_FROM_PASS_ROW macro.
-
-Unknown-chunk handling
-
-Now you get to set the way the library processes unknown chunks in the
-input PNG stream. Both known and unknown chunks will be read.  Normal
-behavior is that known chunks will be parsed into information in
-various info_ptr members while unknown chunks will be discarded. This
-behavior can be wasteful if your application will never use some known
-chunk types. To change this, you can call:
-
-    png_set_keep_unknown_chunks(png_ptr, keep,
-        chunk_list, num_chunks);
-
-    keep       - 0: default unknown chunk handling
-                 1: ignore; do not keep
-                 2: keep only if safe-to-copy
-                 3: keep even if unsafe-to-copy
-
-               You can use these definitions:
-                 PNG_HANDLE_CHUNK_AS_DEFAULT   0
-                 PNG_HANDLE_CHUNK_NEVER        1
-                 PNG_HANDLE_CHUNK_IF_SAFE      2
-                 PNG_HANDLE_CHUNK_ALWAYS       3
-
-    chunk_list - list of chunks affected (a byte string,
-                 five bytes per chunk, NULL or '\0' if
-                 num_chunks is positive; ignored if
-                 numchunks <= 0).
-
-    num_chunks - number of chunks affected; if 0, all
-                 unknown chunks are affected.  If positive,
-                 only the chunks in the list are affected,
-                 and if negative all unknown chunks and
-                 all known chunks except for the IHDR,
-                 PLTE, tRNS, IDAT, and IEND chunks are
-                 affected.
-
-Unknown chunks declared in this way will be saved as raw data onto a
-list of png_unknown_chunk structures.  If a chunk that is normally
-known to libpng is named in the list, it will be handled as unknown,
-according to the "keep" directive.  If a chunk is named in successive
-instances of png_set_keep_unknown_chunks(), the final instance will
-take precedence.  The IHDR and IEND chunks should not be named in
-chunk_list; if they are, libpng will process them normally anyway.
-If you know that your application will never make use of some particular
-chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
-
-Here is an example of the usage of png_set_keep_unknown_chunks(),
-where the private "vpAg" chunk will later be processed by a user chunk
-callback function:
-
-    png_byte vpAg[5]={118, 112,  65, 103, (png_byte) '\0'};
-
-    #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
-      png_byte unused_chunks[]=
-      {
-        104,  73,  83,  84, (png_byte) '\0',   /* hIST */
-        105,  84,  88, 116, (png_byte) '\0',   /* iTXt */
-        112,  67,  65,  76, (png_byte) '\0',   /* pCAL */
-        115,  67,  65,  76, (png_byte) '\0',   /* sCAL */
-        115,  80,  76,  84, (png_byte) '\0',   /* sPLT */
-        116,  73,  77,  69, (png_byte) '\0',   /* tIME */
-      };
-    #endif
-
-    ...
-
-    #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
-      /* ignore all unknown chunks
-       * (use global setting "2" for libpng16 and earlier):
-       */
-      png_set_keep_unknown_chunks(read_ptr, 2, NULL, 0);
-
-      /* except for vpAg: */
-      png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
-
-      /* also ignore unused known chunks: */
-      png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
-         (int)(sizeof unused_chunks)/5);
-    #endif
-
-User limits
-
-The PNG specification allows the width and height of an image to be as
-large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
-For safety, libpng imposes a default limit of 1 million rows and columns.
-Larger images will be rejected immediately with a png_error() call. If
-you wish to change these limits, you can use
-
-   png_set_user_limits(png_ptr, width_max, height_max);
-
-to set your own limits (libpng may reject some very wide images
-anyway because of potential buffer overflow conditions).
-
-You should put this statement after you create the PNG structure and
-before calling png_read_info(), png_read_png(), or png_process_data().
-
-When writing a PNG datastream, put this statement before calling
-png_write_info() or png_write_png().
-
-If you need to retrieve the limits that are being applied, use
-
-   width_max = png_get_user_width_max(png_ptr);
-   height_max = png_get_user_height_max(png_ptr);
-
-The PNG specification sets no limit on the number of ancillary chunks
-allowed in a PNG datastream.  By default, libpng imposes a limit of
-a total of 1000 sPLT, tEXt, iTXt, zTXt, and unknown chunks to be stored.
-If you have set up both info_ptr and end_info_ptr, the limit applies
-separately to each.  You can change the limit on the total number of such
-chunks that will be stored, with
-
-   png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
-
-where 0x7fffffffL means unlimited.  You can retrieve this limit with
-
-   chunk_cache_max = png_get_chunk_cache_max(png_ptr);
-
-Libpng imposes a limit of 8 Megabytes (8,000,000 bytes) on the amount of
-memory that any chunk other than IDAT can occupy, originally or when
-decompressed (prior to libpng-1.6.32 the limit was only applied to compressed
-chunks after decompression). You can change this limit with
-
-   png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max);
-
-and you can retrieve the limit with
-
-   chunk_malloc_max = png_get_chunk_malloc_max(png_ptr);
-
-Any chunks that would cause either of these limits to be exceeded will
-be ignored.
-
-Information about your system
-
-If you intend to display the PNG or to incorporate it in other image data you
-need to tell libpng information about your display or drawing surface so that
-libpng can convert the values in the image to match the display.
-
-From libpng-1.5.4 this information can be set before reading the PNG file
-header.  In earlier versions png_set_gamma() existed but behaved incorrectly if
-called before the PNG file header had been read and png_set_alpha_mode() did not
-exist.
-
-If you need to support versions prior to libpng-1.5.4 test the version number
-as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
-described in the appropriate manual page.
-
-You give libpng the encoding expected by your system expressed as a 'gamma'
-value.  You can also specify a default encoding for the PNG file in
-case the required information is missing from the file.  By default libpng
-assumes that the PNG data matches your system, to keep this default call:
-
-   png_set_gamma(png_ptr, screen_gamma, output_gamma);
-
-or you can use the fixed point equivalent:
-
-   png_set_gamma_fixed(png_ptr, PNG_FP_1*screen_gamma,
-      PNG_FP_1*output_gamma);
-
-If you don't know the gamma for your system it is probably 2.2 - a good
-approximation to the IEC standard for display systems (sRGB).  If images are
-too contrasty or washed out you got the value wrong - check your system
-documentation!
-
-Many systems permit the system gamma to be changed via a lookup table in the
-display driver, a few systems, including older Macs, change the response by
-default.  As of 1.5.4 three special values are available to handle common
-situations:
-
-   PNG_DEFAULT_sRGB: Indicates that the system conforms to the
-                     IEC 61966-2-1 standard.  This matches almost
-                     all systems.
-   PNG_GAMMA_MAC_18: Indicates that the system is an older
-                     (pre Mac OS 10.6) Apple Macintosh system with
-                     the default settings.
-   PNG_GAMMA_LINEAR: Just the fixed point value for 1.0 - indicates
-                     that the system expects data with no gamma
-                     encoding.
-
-You would use the linear (unencoded) value if you need to process the pixel
-values further because this avoids the need to decode and re-encode each
-component value whenever arithmetic is performed.  A lot of graphics software
-uses linear values for this reason, often with higher precision component values
-to preserve overall accuracy.
-
-
-The output_gamma value expresses how to decode the output values, not how
-they are encoded.  The values used correspond to the normal numbers used to
-describe the overall gamma of a computer display system; for example 2.2 for
-an sRGB conformant system.  The values are scaled by 100000 in the _fixed
-version of the API (so 220000 for sRGB.)
-
-The inverse of the value is always used to provide a default for the PNG file
-encoding if it has no gAMA chunk and if png_set_gamma() has not been called
-to override the PNG gamma information.
-
-When the ALPHA_OPTIMIZED mode is selected the output gamma is used to encode
-opaque pixels however pixels with lower alpha values are not encoded,
-regardless of the output gamma setting.
-
-When the standard Porter Duff handling is requested with mode 1 the output
-encoding is set to be linear and the output_gamma value is only relevant
-as a default for input data that has no gamma information.  The linear output
-encoding will be overridden if png_set_gamma() is called - the results may be
-highly unexpected!
-
-The following numbers are derived from the sRGB standard and the research
-behind it.  sRGB is defined to be approximated by a PNG gAMA chunk value of
-0.45455 (1/2.2) for PNG.  The value implicitly includes any viewing
-correction required to take account of any differences in the color
-environment of the original scene and the intended display environment; the
-value expresses how to *decode* the image for display, not how the original
-data was *encoded*.
-
-sRGB provides a peg for the PNG standard by defining a viewing environment.
-sRGB itself, and earlier TV standards, actually use a more complex transform
-(a linear portion then a gamma 2.4 power law) than PNG can express.  (PNG is
-limited to simple power laws.)  By saying that an image for direct display on
-an sRGB conformant system should be stored with a gAMA chunk value of 45455
-(11.3.3.2 and 11.3.3.5 of the ISO PNG specification) the PNG specification
-makes it possible to derive values for other display systems and
-environments.
-
-The Mac value is deduced from the sRGB based on an assumption that the actual
-extra viewing correction used in early Mac display systems was implemented as
-a power 1.45 lookup table.
-
-Any system where a programmable lookup table is used or where the behavior of
-the final display device characteristics can be changed requires system
-specific code to obtain the current characteristic.  However this can be
-difficult and most PNG gamma correction only requires an approximate value.
-
-By default, if png_set_alpha_mode() is not called, libpng assumes that all
-values are unencoded, linear, values and that the output device also has a
-linear characteristic.  This is only very rarely correct - it is invariably
-better to call png_set_alpha_mode() with PNG_DEFAULT_sRGB than rely on the
-default if you don't know what the right answer is!
-
-The special value PNG_GAMMA_MAC_18 indicates an older Mac system (pre Mac OS
-10.6) which used a correction table to implement a somewhat lower gamma on an
-otherwise sRGB system.
-
-Both these values are reserved (not simple gamma values) in order to allow
-more precise correction internally in the future.
-
-NOTE: the values can be passed to either the fixed or floating
-point APIs, but the floating point API will also accept floating point
-values.
-
-The second thing you may need to tell libpng about is how your system handles
-alpha channel information.  Some, but not all, PNG files contain an alpha
-channel.  To display these files correctly you need to compose the data onto a
-suitable background, as described in the PNG specification.
-
-Libpng only supports composing onto a single color (using png_set_background;
-see below).  Otherwise you must do the composition yourself and, in this case,
-you may need to call png_set_alpha_mode:
-
-   #if PNG_LIBPNG_VER >= 10504
-      png_set_alpha_mode(png_ptr, mode, screen_gamma);
-   #else
-      png_set_gamma(png_ptr, screen_gamma, 1.0/screen_gamma);
-   #endif
-
-The screen_gamma value is the same as the argument to png_set_gamma; however,
-how it affects the output depends on the mode.  png_set_alpha_mode() sets the
-file gamma default to 1/screen_gamma, so normally you don't need to call
-png_set_gamma.  If you need different defaults call png_set_gamma() before
-png_set_alpha_mode() - if you call it after it will override the settings made
-by png_set_alpha_mode().
-
-The mode is as follows:
-
-    PNG_ALPHA_PNG: The data is encoded according to the PNG
-specification.  Red, green and blue, or gray, components are
-gamma encoded color values and are not premultiplied by the
-alpha value.  The alpha value is a linear measure of the
-contribution of the pixel to the corresponding final output pixel.
-
-You should normally use this format if you intend to perform
-color correction on the color values; most, maybe all, color
-correction software has no handling for the alpha channel and,
-anyway, the math to handle pre-multiplied component values is
-unnecessarily complex.
-
-Before you do any arithmetic on the component values you need
-to remove the gamma encoding and multiply out the alpha
-channel.  See the PNG specification for more detail.  It is
-important to note that when an image with an alpha channel is
-scaled, linear encoded, pre-multiplied component values must
-be used!
-
-The remaining modes assume you don't need to do any further color correction or
-that if you do, your color correction software knows all about alpha (it
-probably doesn't!).  They 'associate' the alpha with the color information by
-storing color channel values that have been scaled by the alpha.  The
-advantage is that the color channels can be resampled (the image can be
-scaled) in this form.  The disadvantage is that normal practice is to store
-linear, not (gamma) encoded, values and this requires 16-bit channels for
-still images rather than the 8-bit channels that are just about sufficient if
-gamma encoding is used.  In addition all non-transparent pixel values,
-including completely opaque ones, must be gamma encoded to produce the final
-image.  These are the 'STANDARD', 'ASSOCIATED' or 'PREMULTIPLIED' modes
-described below (the latter being the two common names for associated alpha
-color channels). Note that PNG files always contain non-associated color
-channels; png_set_alpha_mode() with one of the modes causes the decoder to
-convert the pixels to an associated form before returning them to your
-application. 
-
-Since it is not necessary to perform arithmetic on opaque color values so
-long as they are not to be resampled and are in the final color space it is
-possible to optimize the handling of alpha by storing the opaque pixels in
-the PNG format (adjusted for the output color space) while storing partially
-opaque pixels in the standard, linear, format.  The accuracy required for
-standard alpha composition is relatively low, because the pixels are
-isolated, therefore typically the accuracy loss in storing 8-bit linear
-values is acceptable.  (This is not true if the alpha channel is used to
-simulate transparency over large areas - use 16 bits or the PNG mode in
-this case!)  This is the 'OPTIMIZED' mode.  For this mode a pixel is
-treated as opaque only if the alpha value is equal to the maximum value.
-
-    PNG_ALPHA_STANDARD:  The data libpng produces is encoded in the
-standard way assumed by most correctly written graphics software.
-The gamma encoding will be removed by libpng and the
-linear component values will be pre-multiplied by the
-alpha channel.
-
-With this format the final image must be re-encoded to
-match the display gamma before the image is displayed.
-If your system doesn't do that, yet still seems to
-perform arithmetic on the pixels without decoding them,
-it is broken - check out the modes below.
-
-With PNG_ALPHA_STANDARD libpng always produces linear
-component values, whatever screen_gamma you supply.  The
-screen_gamma value is, however, used as a default for
-the file gamma if the PNG file has no gamma information.
-
-If you call png_set_gamma() after png_set_alpha_mode() you
-will override the linear encoding.  Instead the
-pre-multiplied pixel values will be gamma encoded but
-the alpha channel will still be linear.  This may
-actually match the requirements of some broken software,
-but it is unlikely.
-
-While linear 8-bit data is often used it has
-insufficient precision for any image with a reasonable
-dynamic range.  To avoid problems, and if your software
-supports it, use png_set_expand_16() to force all
-components to 16 bits.
-
-    PNG_ALPHA_OPTIMIZED: This mode is the same as PNG_ALPHA_STANDARD
-except that completely opaque pixels are gamma encoded according to
-the screen_gamma value.  Pixels with alpha less than 1.0
-will still have linear components.
-
-Use this format if you have control over your
-compositing software and so don't do other arithmetic
-(such as scaling) on the data you get from libpng.  Your
-compositing software can simply copy opaque pixels to
-the output but still has linear values for the
-non-opaque pixels.
-
-In normal compositing, where the alpha channel encodes
-partial pixel coverage (as opposed to broad area
-translucency), the inaccuracies of the 8-bit
-representation of non-opaque pixels are irrelevant.
-
-You can also try this format if your software is broken;
-it might look better.
-
-    PNG_ALPHA_BROKEN: This is PNG_ALPHA_STANDARD; however, all component
-values, including the alpha channel are gamma encoded.  This is
-broken because, in practice, no implementation that uses this choice
-correctly undoes the encoding before handling alpha composition.  Use this
-choice only if other serious errors in the software or hardware you use
-mandate it.  In most cases of broken software or hardware the bug in the
-final display manifests as a subtle halo around composited parts of the
-image.  You may not even perceive this as a halo; the composited part of
-the image may simply appear separate from the background, as though it had
-been cut out of paper and pasted on afterward.
-
-If you don't have to deal with bugs in software or hardware, or if you can fix
-them, there are three recommended ways of using png_set_alpha_mode():
-
-   png_set_alpha_mode(png_ptr, PNG_ALPHA_PNG,
-       screen_gamma);
-
-You can do color correction on the result (libpng does not currently
-support color correction internally).  When you handle the alpha channel
-you need to undo the gamma encoding and multiply out the alpha.
-
-   png_set_alpha_mode(png_ptr, PNG_ALPHA_STANDARD,
-       screen_gamma);
-   png_set_expand_16(png_ptr);
-
-If you are using the high level interface, don't call png_set_expand_16();
-instead pass PNG_TRANSFORM_EXPAND_16 to the interface.
-
-With this mode you can't do color correction, but you can do arithmetic,
-including composition and scaling, on the data without further processing.
-
-   png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED,
-       screen_gamma);
-
-You can avoid the expansion to 16-bit components with this mode, but you
-lose the ability to scale the image or perform other linear arithmetic.
-All you can do is compose the result onto a matching output.  Since this
-mode is libpng-specific you also need to write your own composition
-software.
-
-The following are examples of calls to png_set_alpha_mode to achieve the
-required overall gamma correction and, where necessary, alpha
-premultiplication.
-
-    png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
-
-Choices for the alpha_mode are
-
-    PNG_ALPHA_PNG           0 /* according to the PNG standard */
-    PNG_ALPHA_STANDARD      1 /* according to Porter/Duff */
-    PNG_ALPHA_ASSOCIATED    1 /* as above; this is the normal practice */
-    PNG_ALPHA_PREMULTIPLIED 1 /* as above */
-    PNG_ALPHA_OPTIMIZED     2 /* 'PNG' for opaque pixels, else 'STANDARD' */
-    PNG_ALPHA_BROKEN        3 /* the alpha channel is gamma encoded */
-
-PNG_ALPHA_PNG is the default libpng handling of the alpha channel. It is not
-pre-multiplied into the color components. In addition the call states
-that the output is for a sRGB system and causes all PNG files without gAMA
-chunks to be assumed to be encoded using sRGB.
-
-    png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
-
-In this case the output is assumed to be something like an sRGB conformant
-display preceeded by a power-law lookup table of power 1.45.  This is how
-early Mac systems behaved.
-
-    png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_GAMMA_LINEAR);
-
-This is the classic Jim Blinn approach and will work in academic
-environments where everything is done by the book.  It has the shortcoming
-of assuming that input PNG data with no gamma information is linear - this
-is unlikely to be correct unless the PNG files were generated locally.
-Most of the time the output precision will be so low as to show
-significant banding in dark areas of the image.
-
-    png_set_expand_16(pp);
-    png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_DEFAULT_sRGB);
-
-This is a somewhat more realistic Jim Blinn inspired approach.  PNG files
-are assumed to have the sRGB encoding if not marked with a gamma value and
-the output is always 16 bits per component.  This permits accurate scaling
-and processing of the data.  If you know that your input PNG files were
-generated locally you might need to replace PNG_DEFAULT_sRGB with the
-correct value for your system.
-
-    png_set_alpha_mode(pp, PNG_ALPHA_OPTIMIZED, PNG_DEFAULT_sRGB);
-
-If you just need to composite the PNG image onto an existing background
-and if you control the code that does this you can use the optimization
-setting.  In this case you just copy completely opaque pixels to the
-output.  For pixels that are not completely transparent (you just skip
-those) you do the composition math using png_composite or png_composite_16
-below then encode the resultant 8-bit or 16-bit values to match the output
-encoding.
-
-    Other cases
-
-If neither the PNG nor the standard linear encoding work for you because
-of the software or hardware you use then you have a big problem.  The PNG
-case will probably result in halos around the image.  The linear encoding
-will probably result in a washed out, too bright, image (it's actually too
-contrasty.)  Try the ALPHA_OPTIMIZED mode above - this will probably
-substantially reduce the halos.  Alternatively try:
-
-    png_set_alpha_mode(pp, PNG_ALPHA_BROKEN, PNG_DEFAULT_sRGB);
-
-This option will also reduce the halos, but there will be slight dark
-halos round the opaque parts of the image where the background is light.
-In the OPTIMIZED mode the halos will be light halos where the background
-is dark.  Take your pick - the halos are unavoidable unless you can get
-your hardware/software fixed!  (The OPTIMIZED approach is slightly
-faster.)
-
-When the default gamma of PNG files doesn't match the output gamma.
-If you have PNG files with no gamma information png_set_alpha_mode allows
-you to provide a default gamma, but it also sets the ouput gamma to the
-matching value.  If you know your PNG files have a gamma that doesn't
-match the output you can take advantage of the fact that
-png_set_alpha_mode always sets the output gamma but only sets the PNG
-default if it is not already set:
-
-    png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
-    png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
-
-The first call sets both the default and the output gamma values, the
-second call overrides the output gamma without changing the default.  This
-is easier than achieving the same effect with png_set_gamma.  You must use
-PNG_ALPHA_PNG for the first call - internal checking in png_set_alpha will
-fire if more than one call to png_set_alpha_mode and png_set_background is
-made in the same read operation, however multiple calls with PNG_ALPHA_PNG
-are ignored.
-
-If you don't need, or can't handle, the alpha channel you can call
-png_set_background() to remove it by compositing against a fixed color.  Don't
-call png_set_strip_alpha() to do this - it will leave spurious pixel values in
-transparent parts of this image.
-
-   png_set_background(png_ptr, &background_color,
-       PNG_BACKGROUND_GAMMA_SCREEN, 0, 1);
-
-The background_color is an RGB or grayscale value according to the data format
-libpng will produce for you.  Because you don't yet know the format of the PNG
-file, if you call png_set_background at this point you must arrange for the
-format produced by libpng to always have 8-bit or 16-bit components and then
-store the color as an 8-bit or 16-bit color as appropriate.  The color contains
-separate gray and RGB component values, so you can let libpng produce gray or
-RGB output according to the input format, but low bit depth grayscale images
-must always be converted to at least 8-bit format.  (Even though low bit depth
-grayscale images can't have an alpha channel they can have a transparent
-color!)
-
-You set the transforms you need later, either as flags to the high level
-interface or libpng API calls for the low level interface.  For reference the
-settings and API calls required are:
-
-8-bit values:
-   PNG_TRANSFORM_SCALE_16 | PNG_EXPAND
-   png_set_expand(png_ptr); png_set_scale_16(png_ptr);
-
-   If you must get exactly the same inaccurate results
-   produced by default in versions prior to libpng-1.5.4,
-   use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr)
-   instead.
-
-16-bit values:
-   PNG_TRANSFORM_EXPAND_16
-   png_set_expand_16(png_ptr);
-
-In either case palette image data will be expanded to RGB.  If you just want
-color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr)
-to the list.
-
-Calling png_set_background before the PNG file header is read will not work
-prior to libpng-1.5.4.  Because the failure may result in unexpected warnings or
-errors it is therefore much safer to call png_set_background after the head has
-been read.  Unfortunately this means that prior to libpng-1.5.4 it cannot be
-used with the high level interface.
-
-The high-level read interface
-
-At this point there are two ways to proceed; through the high-level
-read interface, or through a sequence of low-level read operations.
-You can use the high-level interface if (a) you are willing to read
-the entire image into memory, and (b) the input transformations
-you want to do are limited to the following set:
-
-    PNG_TRANSFORM_IDENTITY      No transformation
-    PNG_TRANSFORM_SCALE_16      Strip 16-bit samples to
-                                8-bit accurately
-    PNG_TRANSFORM_STRIP_16      Chop 16-bit samples to
-                                8-bit less accurately
-    PNG_TRANSFORM_STRIP_ALPHA   Discard the alpha channel
-    PNG_TRANSFORM_PACKING       Expand 1, 2 and 4-bit
-                                samples to bytes
-    PNG_TRANSFORM_PACKSWAP      Change order of packed
-                                pixels to LSB first
-    PNG_TRANSFORM_EXPAND        Perform set_expand()
-    PNG_TRANSFORM_INVERT_MONO   Invert monochrome images
-    PNG_TRANSFORM_SHIFT         Normalize pixels to the
-                                sBIT depth
-    PNG_TRANSFORM_BGR           Flip RGB to BGR, RGBA
-                                to BGRA
-    PNG_TRANSFORM_SWAP_ALPHA    Flip RGBA to ARGB or GA
-                                to AG
-    PNG_TRANSFORM_INVERT_ALPHA  Change alpha from opacity
-                                to transparency
-    PNG_TRANSFORM_SWAP_ENDIAN   Byte-swap 16-bit samples
-    PNG_TRANSFORM_GRAY_TO_RGB   Expand grayscale samples
-                                to RGB (or GA to RGBA)
-    PNG_TRANSFORM_EXPAND_16     Expand samples to 16 bits
-
-(This excludes setting a background color, doing gamma transformation,
-quantizing, and setting filler.)  If this is the case, simply do this:
-
-    png_read_png(png_ptr, info_ptr, png_transforms, NULL)
-
-where png_transforms is an integer containing the bitwise OR of some
-set of transformation flags.  This call is equivalent to png_read_info(),
-followed the set of transformations indicated by the transform mask,
-then png_read_image(), and finally png_read_end().
-
-(The final parameter of this call is not yet used.  Someday it might point
-to transformation parameters required by some future input transform.)
-
-You must use png_transforms and not call any png_set_transform() functions
-when you use png_read_png().
-
-After you have called png_read_png(), you can retrieve the image data
-with
-
-   row_pointers = png_get_rows(png_ptr, info_ptr);
-
-where row_pointers is an array of pointers to the pixel data for each row:
-
-   png_bytep row_pointers[height];
-
-If you know your image size and pixel size ahead of time, you can allocate
-row_pointers prior to calling png_read_png() with
-
-   if (height > PNG_UINT_32_MAX/(sizeof (png_byte)))
-      png_error (png_ptr,
-          "Image is too tall to process in memory");
-
-   if (width > PNG_UINT_32_MAX/pixel_size)
-      png_error (png_ptr,
-          "Image is too wide to process in memory");
-
-   row_pointers = png_malloc(png_ptr,
-       height*(sizeof (png_bytep)));
-
-   for (int i=0; i<height, i++)
-      row_pointers[i]=NULL;  /* security precaution */
-
-   for (int i=0; i<height, i++)
-      row_pointers[i]=png_malloc(png_ptr,
-          width*pixel_size);
-
-   png_set_rows(png_ptr, info_ptr, &row_pointers);
-
-Alternatively you could allocate your image in one big block and define
-row_pointers[i] to point into the proper places in your block, but first
-be sure that your platform is able to allocate such a large buffer:
-
-   /* Guard against integer overflow */
-   if (height > PNG_SIZE_MAX/(width*pixel_size)) {
-        png_error(png_ptr,"image_data buffer would be too large");
-   }
-
-   png_bytep buffer=png_malloc(png_ptr,height*width*pixel_size);
-
-   for (int i=0; i<height, i++)
-      row_pointers[i]=buffer+i*width*pixel_size;
-
-   png_set_rows(png_ptr, info_ptr, &row_pointers);
-
-If you use png_set_rows(), the application is responsible for freeing
-row_pointers (and row_pointers[i], if they were separately allocated).
-
-If you don't allocate row_pointers ahead of time, png_read_png() will
-do it, and it'll be free'ed by libpng when you call png_destroy_*().
-
-The low-level read interface
-
-If you are going the low-level route, you are now ready to read all
-the file information up to the actual image data.  You do this with a
-call to png_read_info().
-
-    png_read_info(png_ptr, info_ptr);
-
-This will process all chunks up to but not including the image data.
-
-This also copies some of the data from the PNG file into the decode structure
-for use in later transformations.  Important information copied in is:
-
-1) The PNG file gamma from the gAMA chunk.  This overwrites the default value
-provided by an earlier call to png_set_gamma or png_set_alpha_mode.
-
-2) Prior to libpng-1.5.4 the background color from a bKGd chunk.  This
-damages the information provided by an earlier call to png_set_background
-resulting in unexpected behavior.  Libpng-1.5.4 no longer does this.
-
-3) The number of significant bits in each component value.  Libpng uses this to
-optimize gamma handling by reducing the internal lookup table sizes.
-
-4) The transparent color information from a tRNS chunk.  This can be modified by
-a later call to png_set_tRNS.
-
-Querying the info structure
-
-Functions are used to get the information from the info_ptr once it
-has been read.  Note that these fields may not be completely filled
-in until png_read_end() has read the chunk data following the image.
-
-    png_get_IHDR(png_ptr, info_ptr, &width, &height,
-       &bit_depth, &color_type, &interlace_type,
-       &compression_type, &filter_method);
-
-    width          - holds the width of the image
-                     in pixels (up to 2^31).
-
-    height         - holds the height of the image
-                     in pixels (up to 2^31).
-
-    bit_depth      - holds the bit depth of one of the
-                     image channels.  (valid values are
-                     1, 2, 4, 8, 16 and depend also on
-                     the color_type.  See also
-                     significant bits (sBIT) below).
-
-    color_type     - describes which color/alpha channels
-                         are present.
-                     PNG_COLOR_TYPE_GRAY
-                        (bit depths 1, 2, 4, 8, 16)
-                     PNG_COLOR_TYPE_GRAY_ALPHA
-                        (bit depths 8, 16)
-                     PNG_COLOR_TYPE_PALETTE
-                        (bit depths 1, 2, 4, 8)
-                     PNG_COLOR_TYPE_RGB
-                        (bit_depths 8, 16)
-                     PNG_COLOR_TYPE_RGB_ALPHA
-                        (bit_depths 8, 16)
-
-                     PNG_COLOR_MASK_PALETTE
-                     PNG_COLOR_MASK_COLOR
-                     PNG_COLOR_MASK_ALPHA
-
-    interlace_type - (PNG_INTERLACE_NONE or
-                     PNG_INTERLACE_ADAM7)
-
-    compression_type - (must be PNG_COMPRESSION_TYPE_BASE
-                     for PNG 1.0)
-
-    filter_method  - (must be PNG_FILTER_TYPE_BASE
-                     for PNG 1.0, and can also be
-                     PNG_INTRAPIXEL_DIFFERENCING if
-                     the PNG datastream is embedded in
-                     a MNG-1.0 datastream)
-
-    Any of width, height, color_type, bit_depth,
-    interlace_type, compression_type, or filter_method can
-    be NULL if you are not interested in their values.
-
-    Note that png_get_IHDR() returns 32-bit data into
-    the application's width and height variables.
-    This is an unsafe situation if these are not png_uint_32
-    variables.  In such situations, the
-    png_get_image_width() and png_get_image_height()
-    functions described below are safer.
-
-    width            = png_get_image_width(png_ptr,
-                         info_ptr);
-
-    height           = png_get_image_height(png_ptr,
-                         info_ptr);
-
-    bit_depth        = png_get_bit_depth(png_ptr,
-                         info_ptr);
-
-    color_type       = png_get_color_type(png_ptr,
-                         info_ptr);
-
-    interlace_type   = png_get_interlace_type(png_ptr,
-                         info_ptr);
-
-    compression_type = png_get_compression_type(png_ptr,
-                         info_ptr);
-
-    filter_method    = png_get_filter_type(png_ptr,
-                         info_ptr);
-
-    channels = png_get_channels(png_ptr, info_ptr);
-
-    channels       - number of channels of info for the
-                     color type (valid values are 1 (GRAY,
-                     PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
-                     4 (RGB_ALPHA or RGB + filler byte))
-
-    rowbytes = png_get_rowbytes(png_ptr, info_ptr);
-
-    rowbytes       - number of bytes needed to hold a row
-                     This value, the bit_depth, color_type,
-                     and the number of channels can change
-                     if you use transforms such as
-                     png_set_expand(). See
-                     png_read_update_info(), below.
-
-    signature = png_get_signature(png_ptr, info_ptr);
-
-    signature      - holds the signature read from the
-                     file (if any).  The data is kept in
-                     the same offset it would be if the
-                     whole signature were read (i.e. if an
-                     application had already read in 4
-                     bytes of signature before starting
-                     libpng, the remaining 4 bytes would
-                     be in signature[4] through signature[7]
-                     (see png_set_sig_bytes())).
-
-These are also important, but their validity depends on whether the chunk
-has been read.  The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
-png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
-data has been read, or zero if it is missing.  The parameters to the
-png_get_<chunk> are set directly if they are simple data types, or a
-pointer into the info_ptr is returned for any complex types.
-
-The colorspace data from gAMA, cHRM, sRGB, iCCP, and sBIT chunks
-is simply returned to give the application information about how the
-image was encoded.  Libpng itself only does transformations using the file
-gamma when combining semitransparent pixels with the background color, and,
-since libpng-1.6.0, when converting between 8-bit sRGB and 16-bit linear pixels
-within the simplified API.  Libpng also uses the file gamma when converting
-RGB to gray, beginning with libpng-1.0.5, if the application calls
-png_set_rgb_to_gray()).
-
-    png_get_PLTE(png_ptr, info_ptr, &palette,
-                     &num_palette);
-
-    palette        - the palette for the file
-                     (array of png_color)
-
-    num_palette    - number of entries in the palette
-
-    png_get_gAMA(png_ptr, info_ptr, &file_gamma);
-    png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma);
-
-    file_gamma     - the gamma at which the file is
-                     written (PNG_INFO_gAMA)
-
-    int_file_gamma - 100,000 times the gamma at which the
-                     file is written
-
-    png_get_cHRM(png_ptr, info_ptr,  &white_x, &white_y, &red_x,
-                     &red_y, &green_x, &green_y, &blue_x, &blue_y)
-    png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z,
-                     &green_X, &green_Y, &green_Z, &blue_X, &blue_Y,
-                     &blue_Z)
-    png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x,
-                     &int_white_y, &int_red_x, &int_red_y,
-                     &int_green_x, &int_green_y, &int_blue_x,
-                     &int_blue_y)
-    png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y,
-                     &int_red_Z, &int_green_X, &int_green_Y,
-                     &int_green_Z, &int_blue_X, &int_blue_Y,
-                     &int_blue_Z)
-
-    {white,red,green,blue}_{x,y}
-                     A color space encoding specified using the
-                     chromaticities of the end points and the
-                     white point. (PNG_INFO_cHRM)
-
-    {red,green,blue}_{X,Y,Z}
-                     A color space encoding specified using the
-                     encoding end points - the CIE tristimulus
-                     specification of the intended color of the red,
-                     green and blue channels in the PNG RGB data.
-                     The white point is simply the sum of the three
-                     end points. (PNG_INFO_cHRM)
-
-    png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
-
-    srgb_intent -    the rendering intent (PNG_INFO_sRGB)
-                     The presence of the sRGB chunk
-                     means that the pixel data is in the
-                     sRGB color space.  This chunk also
-                     implies specific values of gAMA and
-                     cHRM.
-
-    png_get_iCCP(png_ptr, info_ptr, &name,
-       &compression_type, &profile, &proflen);
-
-    name             - The profile name.
-
-    compression_type - The compression type; always
-                       PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
-                       You may give NULL to this argument to
-                       ignore it.
-
-    profile          - International Color Consortium color
-                       profile data. May contain NULs.
-
-    proflen          - length of profile data in bytes.
-
-    png_get_sBIT(png_ptr, info_ptr, &sig_bit);
-
-    sig_bit        - the number of significant bits for
-                     (PNG_INFO_sBIT) each of the gray,
-                     red, green, and blue channels,
-                     whichever are appropriate for the
-                     given color type (png_color_16)
-
-    png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
-                     &num_trans, &trans_color);
-
-    trans_alpha    - array of alpha (transparency)
-                     entries for palette (PNG_INFO_tRNS)
-
-    num_trans      - number of transparent entries
-                     (PNG_INFO_tRNS)
-
-    trans_color    - graylevel or color sample values of
-                     the single transparent color for
-                     non-paletted images (PNG_INFO_tRNS)
-
-    png_get_eXIf_1(png_ptr, info_ptr, &num_exif, &exif);
-                     (PNG_INFO_eXIf)
-
-    exif           - Exif profile (array of png_byte)
-
-    png_get_hIST(png_ptr, info_ptr, &hist);
-                     (PNG_INFO_hIST)
-
-    hist           - histogram of palette (array of
-                     png_uint_16)
-
-    png_get_tIME(png_ptr, info_ptr, &mod_time);
-
-    mod_time       - time image was last modified
-                    (PNG_VALID_tIME)
-
-    png_get_bKGD(png_ptr, info_ptr, &background);
-
-    background     - background color (of type
-                     png_color_16p) (PNG_VALID_bKGD)
-                     valid 16-bit red, green and blue
-                     values, regardless of color_type
-
-    num_comments   = png_get_text(png_ptr, info_ptr,
-                     &text_ptr, &num_text);
-
-    num_comments   - number of comments
-
-    text_ptr       - array of png_text holding image
-                     comments
-
-    text_ptr[i].compression - type of compression used
-                 on "text" PNG_TEXT_COMPRESSION_NONE
-                           PNG_TEXT_COMPRESSION_zTXt
-                           PNG_ITXT_COMPRESSION_NONE
-                           PNG_ITXT_COMPRESSION_zTXt
-
-    text_ptr[i].key   - keyword for comment.  Must contain
-                         1-79 characters.
-
-    text_ptr[i].text  - text comments for current
-                         keyword.  Can be empty.
-
-    text_ptr[i].text_length - length of text string,
-                 after decompression, 0 for iTXt
-
-    text_ptr[i].itxt_length - length of itxt string,
-                 after decompression, 0 for tEXt/zTXt
-
-    text_ptr[i].lang  - language of comment (empty
-                         string for unknown).
-
-    text_ptr[i].lang_key  - keyword in UTF-8
-                         (empty string for unknown).
-
-    Note that the itxt_length, lang, and lang_key
-    members of the text_ptr structure only exist when the
-    library is built with iTXt chunk support.  Prior to
-    libpng-1.4.0 the library was built by default without
-    iTXt support. Also note that when iTXt is supported,
-    they contain NULL pointers when the "compression"
-    field contains PNG_TEXT_COMPRESSION_NONE or
-    PNG_TEXT_COMPRESSION_zTXt.
-
-    num_text       - number of comments (same as
-                     num_comments; you can put NULL here
-                     to avoid the duplication)
-
-    Note while png_set_text() will accept text, language,
-    and translated keywords that can be NULL pointers, the
-    structure returned by png_get_text will always contain
-    regular zero-terminated C strings.  They might be
-    empty strings but they will never be NULL pointers.
-
-    num_spalettes = png_get_sPLT(png_ptr, info_ptr,
-       &palette_ptr);
-
-    num_spalettes  - number of sPLT chunks read.
-
-    palette_ptr    - array of palette structures holding
-                     contents of one or more sPLT chunks
-                     read.
-
-    png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
-       &unit_type);
-
-    offset_x       - positive offset from the left edge
-                     of the screen (can be negative)
-
-    offset_y       - positive offset from the top edge
-                     of the screen (can be negative)
-
-    unit_type      - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
-
-    png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
-       &unit_type);
-
-    res_x          - pixels/unit physical resolution in
-                     x direction
-
-    res_y          - pixels/unit physical resolution in
-                     x direction
-
-    unit_type      - PNG_RESOLUTION_UNKNOWN,
-                     PNG_RESOLUTION_METER
-
-    png_get_sCAL(png_ptr, info_ptr, &unit, &width,
-       &height)
-
-    unit        - physical scale units (an integer)
-
-    width       - width of a pixel in physical scale units
-
-    height      - height of a pixel in physical scale units
-                 (width and height are doubles)
-
-    png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
-       &height)
-
-    unit        - physical scale units (an integer)
-
-    width       - width of a pixel in physical scale units
-                  (expressed as a string)
-
-    height      - height of a pixel in physical scale units
-                 (width and height are strings like "2.54")
-
-    num_unknown_chunks = png_get_unknown_chunks(png_ptr,
-       info_ptr, &unknowns)
-
-    unknowns          - array of png_unknown_chunk
-                        structures holding unknown chunks
-
-    unknowns[i].name  - name of unknown chunk
-
-    unknowns[i].data  - data of unknown chunk
-
-    unknowns[i].size  - size of unknown chunk's data
-
-    unknowns[i].location - position of chunk in file
-
-    The value of "i" corresponds to the order in which the
-    chunks were read from the PNG file or inserted with the
-    png_set_unknown_chunks() function.
-
-    The value of "location" is a bitwise "or" of
-
-         PNG_HAVE_IHDR  (0x01)
-         PNG_HAVE_PLTE  (0x02)
-         PNG_AFTER_IDAT (0x08)
-
-The data from the pHYs chunk can be retrieved in several convenient
-forms:
-
-    res_x = png_get_x_pixels_per_meter(png_ptr,
-       info_ptr)
-
-    res_y = png_get_y_pixels_per_meter(png_ptr,
-       info_ptr)
-
-    res_x_and_y = png_get_pixels_per_meter(png_ptr,
-       info_ptr)
-
-    res_x = png_get_x_pixels_per_inch(png_ptr,
-       info_ptr)
-
-    res_y = png_get_y_pixels_per_inch(png_ptr,
-       info_ptr)
-
-    res_x_and_y = png_get_pixels_per_inch(png_ptr,
-       info_ptr)
-
-    aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
-       info_ptr)
-
-    Each of these returns 0 [signifying "unknown"] if
-       the data is not present or if res_x is 0;
-       res_x_and_y is 0 if res_x != res_y
-
-    Note that because of the way the resolutions are
-       stored internally, the inch conversions won't
-       come out to exactly even number.  For example,
-       72 dpi is stored as 0.28346 pixels/meter, and
-       when this is retrieved it is 71.9988 dpi, so
-       be sure to round the returned value appropriately
-       if you want to display a reasonable-looking result.
-
-The data from the oFFs chunk can be retrieved in several convenient
-forms:
-
-    x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
-
-    y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
-
-    x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
-
-    y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
-
-    Each of these returns 0 [signifying "unknown" if both
-       x and y are 0] if the data is not present or if the
-       chunk is present but the unit is the pixel.  The
-       remark about inexact inch conversions applies here
-       as well, because a value in inches can't always be
-       converted to microns and back without some loss
-       of precision.
-
-For more information, see the
-PNG specification for chunk contents.  Be careful with trusting
-rowbytes, as some of the transformations could increase the space
-needed to hold a row (expand, filler, gray_to_rgb, etc.).
-See png_read_update_info(), below.
-
-A quick word about text_ptr and num_text.  PNG stores comments in
-keyword/text pairs, one pair per chunk, with no limit on the number
-of text chunks, and a 2^31 byte limit on their size.  While there are
-suggested keywords, there is no requirement to restrict the use to these
-strings.  It is strongly suggested that keywords and text be sensible
-to humans (that's the point), so don't use abbreviations.  Non-printing
-symbols are not allowed.  See the PNG specification for more details.
-There is also no requirement to have text after the keyword.
-
-Keywords should be limited to 79 Latin-1 characters without leading or
-trailing spaces, but non-consecutive spaces are allowed within the
-keyword.  It is possible to have the same keyword any number of times.
-The text_ptr is an array of png_text structures, each holding a
-pointer to a language string, a pointer to a keyword and a pointer to
-a text string.  The text string, language code, and translated
-keyword may be empty or NULL pointers.  The keyword/text
-pairs are put into the array in the order that they are received.
-However, some or all of the text chunks may be after the image, so, to
-make sure you have read all the text chunks, don't mess with these
-until after you read the stuff after the image.  This will be
-mentioned again below in the discussion that goes with png_read_end().
-
-Input transformations
-
-After you've read the header information, you can set up the library
-to handle any special transformations of the image data.  The various
-ways to transform the data will be described in the order that they
-should occur.  This is important, as some of these change the color
-type and/or bit depth of the data, and some others only work on
-certain color types and bit depths.
-
-Transformations you request are ignored if they don't have any meaning for a
-particular input data format.  However some transformations can have an effect
-as a result of a previous transformation.  If you specify a contradictory set of
-transformations, for example both adding and removing the alpha channel, you
-cannot predict the final result.
-
-The color used for the transparency values should be supplied in the same
-format/depth as the current image data.  It is stored in the same format/depth
-as the image data in a tRNS chunk, so this is what libpng expects for this data.
-
-The color used for the background value depends on the need_expand argument as
-described below.
-
-Data will be decoded into the supplied row buffers packed into bytes
-unless the library has been told to transform it into another format.
-For example, 4 bit/pixel paletted or grayscale data will be returned
-2 pixels/byte with the leftmost pixel in the high-order bits of the byte,
-unless png_set_packing() is called.  8-bit RGB data will be stored
-in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
-is called to insert filler bytes, either before or after each RGB triplet.
-
-16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
-byte of the color value first, unless png_set_scale_16() is called to
-transform it to regular RGB RGB triplets, or png_set_filler() or
-png_set_add alpha() is called to insert two filler bytes, either before
-or after each RRGGBB triplet.  Similarly, 8-bit or 16-bit grayscale data can
-be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(),
-or png_set_scale_16().
-
-The following code transforms grayscale images of less than 8 to 8 bits,
-changes paletted images to RGB, and adds a full alpha channel if there is
-transparency information in a tRNS chunk.  This is most useful on
-grayscale images with bit depths of 2 or 4 or if there is a multiple-image
-viewing application that wishes to treat all images in the same way.
-
-    if (color_type == PNG_COLOR_TYPE_PALETTE)
-        png_set_palette_to_rgb(png_ptr);
-
-    if (png_get_valid(png_ptr, info_ptr,
-        PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
-
-    if (color_type == PNG_COLOR_TYPE_GRAY &&
-        bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
-
-The first two functions are actually aliases for png_set_expand(), added
-in libpng version 1.0.4, with the function names expanded to improve code
-readability.  In some future version they may actually do different
-things.
-
-As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
-added.  It expands the sample depth without changing tRNS to alpha.
-
-As of libpng version 1.5.2, png_set_expand_16() was added.  It behaves as
-png_set_expand(); however, the resultant channels have 16 bits rather than 8.
-Use this when the output color or gray channels are made linear to avoid fairly
-severe accuracy loss.
-
-   if (bit_depth < 16)
-      png_set_expand_16(png_ptr);
-
-PNG can have files with 16 bits per channel.  If you only can handle
-8 bits per channel, this will strip the pixels down to 8-bit.
-
-    if (bit_depth == 16)
-#if PNG_LIBPNG_VER >= 10504
-       png_set_scale_16(png_ptr);
-#else
-       png_set_strip_16(png_ptr);
-#endif
-
-(The more accurate "png_set_scale_16()" API became available in libpng version
-1.5.4).
-
-If you need to process the alpha channel on the image separately from the image
-data (for example if you convert it to a bitmap mask) it is possible to have
-libpng strip the channel leaving just RGB or gray data:
-
-    if (color_type & PNG_COLOR_MASK_ALPHA)
-       png_set_strip_alpha(png_ptr);
-
-If you strip the alpha channel you need to find some other way of dealing with
-the information.  If, instead, you want to convert the image to an opaque
-version with no alpha channel use png_set_background; see below.
-
-As of libpng version 1.5.2, almost all useful expansions are supported, the
-major ommissions are conversion of grayscale to indexed images (which can be
-done trivially in the application) and conversion of indexed to grayscale (which
-can be done by a trivial manipulation of the palette.)
-
-In the following table, the 01 means grayscale with depth<8, 31 means
-indexed with depth<8, other numerals represent the color type, "T" means
-the tRNS chunk is present, A means an alpha channel is present, and O
-means tRNS or alpha is present but all pixels in the image are opaque.
-
-  FROM  01  31   0  0T  0O   2  2T  2O   3  3T  3O  4A  4O  6A  6O
-   TO
-   01    -  [G]  -   -   -   -   -   -   -   -   -   -   -   -   -
-   31   [Q]  Q  [Q] [Q] [Q]  Q   Q   Q   Q   Q   Q  [Q] [Q]  Q   Q
-    0    1   G   +   .   .   G   G   G   G   G   G   B   B  GB  GB
-   0T    lt  Gt  t   +   .   Gt  G   G   Gt  G   G   Bt  Bt GBt GBt
-   0O    lt  Gt  t   .   +   Gt  Gt  G   Gt  Gt  G   Bt  Bt GBt GBt
-    2    C   P   C   C   C   +   .   .   C   -   -  CB  CB   B   B
-   2T    Ct  -   Ct  C   C   t   +   t   -   -   -  CBt CBt  Bt  Bt
-   2O    Ct  -   Ct  C   C   t   t   +   -   -   -  CBt CBt  Bt  Bt
-    3   [Q]  p  [Q] [Q] [Q]  Q   Q   Q   +   .   .  [Q] [Q]  Q   Q
-   3T   [Qt] p  [Qt][Q] [Q]  Qt  Qt  Qt  t   +   t  [Qt][Qt] Qt  Qt
-   3O   [Qt] p  [Qt][Q] [Q]  Qt  Qt  Qt  t   t   +  [Qt][Qt] Qt  Qt
-   4A    lA  G   A   T   T   GA  GT  GT  GA  GT  GT  +   BA  G  GBA
-   4O    lA GBA  A   T   T   GA  GT  GT  GA  GT  GT  BA  +  GBA  G
-   6A    CA  PA  CA  C   C   A   T  tT   PA  P   P   C  CBA  +   BA
-   6O    CA PBA  CA  C   C   A  tT   T   PA  P   P  CBA  C   BA  +
-
-Within the matrix,
-     "+" identifies entries where 'from' and 'to' are the same.
-     "-" means the transformation is not supported.
-     "." means nothing is necessary (a tRNS chunk can just be ignored).
-     "t" means the transformation is obtained by png_set_tRNS.
-     "A" means the transformation is obtained by png_set_add_alpha().
-     "X" means the transformation is obtained by png_set_expand().
-     "1" means the transformation is obtained by
-         png_set_expand_gray_1_2_4_to_8() (and by png_set_expand()
-         if there is no transparency in the original or the final
-         format).
-     "C" means the transformation is obtained by png_set_gray_to_rgb().
-     "G" means the transformation is obtained by png_set_rgb_to_gray().
-     "P" means the transformation is obtained by
-         png_set_expand_palette_to_rgb().
-     "p" means the transformation is obtained by png_set_packing().
-     "Q" means the transformation is obtained by png_set_quantize().
-     "T" means the transformation is obtained by
-         png_set_tRNS_to_alpha().
-     "B" means the transformation is obtained by
-         png_set_background(), or png_strip_alpha().
-
-When an entry has multiple transforms listed all are required to cause the
-right overall transformation.  When two transforms are separated by a comma
-either will do the job.  When transforms are enclosed in [] the transform should
-do the job but this is currently unimplemented - a different format will result
-if the suggested transformations are used.
-
-In PNG files, the alpha channel in an image
-is the level of opacity.  If you need the alpha channel in an image to
-be the level of transparency instead of opacity, you can invert the
-alpha channel (or the tRNS chunk data) after it's read, so that 0 is
-fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
-images) is fully transparent, with
-
-    png_set_invert_alpha(png_ptr);
-
-PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
-they can, resulting in, for example, 8 pixels per byte for 1 bit
-files.  This code expands to 1 pixel per byte without changing the
-values of the pixels:
-
-    if (bit_depth < 8)
-       png_set_packing(png_ptr);
-
-PNG files have possible bit depths of 1, 2, 4, 8, and 16.  All pixels
-stored in a PNG image have been "scaled" or "shifted" up to the next
-higher possible bit depth (e.g. from 5 bits/sample in the range [0,31]
-to 8 bits/sample in the range [0, 255]).  However, it is also possible
-to convert the PNG pixel data back to the original bit depth of the
-image.  This call reduces the pixels back down to the original bit depth:
-
-    png_color_8p sig_bit;
-
-    if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
-       png_set_shift(png_ptr, sig_bit);
-
-PNG files store 3-color pixels in red, green, blue order.  This code
-changes the storage of the pixels to blue, green, red:
-
-    if (color_type == PNG_COLOR_TYPE_RGB ||
-        color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-       png_set_bgr(png_ptr);
-
-PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
-into 4 or 8 bytes for windowing systems that need them in this format:
-
-    if (color_type == PNG_COLOR_TYPE_RGB)
-       png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
-
-where "filler" is the 8-bit or 16-bit number to fill with, and the location
-is either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
-you want the filler before the RGB or after. When filling an 8-bit pixel,
-the least significant 8 bits of the number are used, if a 16-bit number is
-supplied.  This transformation does not affect images that already have full
-alpha channels.  To add an opaque alpha channel, use filler=0xffff and
-PNG_FILLER_AFTER which will generate RGBA pixels.
-
-Note that png_set_filler() does not change the color type.  If you want
-to do that, you can add a true alpha channel with
-
-    if (color_type == PNG_COLOR_TYPE_RGB ||
-       color_type == PNG_COLOR_TYPE_GRAY)
-       png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
-
-where "filler" contains the alpha value to assign to each pixel.
-The png_set_add_alpha() function was added in libpng-1.2.7.
-
-If you are reading an image with an alpha channel, and you need the
-data as ARGB instead of the normal PNG format RGBA:
-
-    if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-       png_set_swap_alpha(png_ptr);
-
-For some uses, you may want a grayscale image to be represented as
-RGB.  This code will do that conversion:
-
-    if (color_type == PNG_COLOR_TYPE_GRAY ||
-        color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-       png_set_gray_to_rgb(png_ptr);
-
-Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
-with alpha.
-
-    if (color_type == PNG_COLOR_TYPE_RGB ||
-        color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-       png_set_rgb_to_gray(png_ptr, error_action,
-          double red_weight, double green_weight);
-
-    error_action = 1: silently do the conversion
-
-    error_action = 2: issue a warning if the original
-                      image has any pixel where
-                      red != green or red != blue
-
-    error_action = 3: issue an error and abort the
-                      conversion if the original
-                      image has any pixel where
-                      red != green or red != blue
-
-    red_weight:       weight of red component
-
-    green_weight:     weight of green component
-                      If either weight is negative, default
-                      weights are used.
-
-In the corresponding fixed point API the red_weight and green_weight values are
-simply scaled by 100,000:
-
-    png_set_rgb_to_gray(png_ptr, error_action,
-       png_fixed_point red_weight,
-       png_fixed_point green_weight);
-
-If you have set error_action = 1 or 2, you can
-later check whether the image really was gray, after processing
-the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
-It will return a png_byte that is zero if the image was gray or
-1 if there were any non-gray pixels.  Background and sBIT data
-will be silently converted to grayscale, using the green channel
-data for sBIT, regardless of the error_action setting.
-
-The default values come from the PNG file cHRM chunk if present; otherwise, the
-defaults correspond to the ITU-R recommendation 709, and also the sRGB color
-space, as recommended in the Charles Poynton's Colour FAQ,
-Copyright (c) 2006-11-28 Charles Poynton, in section 9:
-
-<http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
-
-    Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
-
-Previous versions of this document, 1998 through 2002, recommended a slightly
-different formula:
-
-    Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
-
-Libpng uses an integer approximation:
-
-    Y = (6968 * R + 23434 * G + 2366 * B)/32768
-
-The calculation is done in a linear colorspace, if the image gamma
-can be determined.
-
-The png_set_background() function has been described already; it tells libpng to
-composite images with alpha or simple transparency against the supplied
-background color.  For compatibility with versions of libpng earlier than
-libpng-1.5.4 it is recommended that you call the function after reading the file
-header, even if you don't want to use the color in a bKGD chunk, if one exists.
-
-If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
-you may use this color, or supply another color more suitable for
-the current display (e.g., the background color from a web page).  You
-need to tell libpng how the color is represented, both the format of the
-component values in the color (the number of bits) and the gamma encoding of the
-color.  The function takes two arguments, background_gamma_mode and need_expand
-to convey this information; however, only two combinations are likely to be
-useful:
-
-    png_color_16 my_background;
-    png_color_16p image_background;
-
-    if (png_get_bKGD(png_ptr, info_ptr, &image_background))
-       png_set_background(png_ptr, image_background,
-           PNG_BACKGROUND_GAMMA_FILE, 1/*needs to be expanded*/, 1);
-    else
-       png_set_background(png_ptr, &my_background,
-           PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1);
-
-The second call was described above - my_background is in the format of the
-final, display, output produced by libpng.  Because you now know the format of
-the PNG it is possible to avoid the need to choose either 8-bit or 16-bit
-output and to retain palette images (the palette colors will be modified
-appropriately and the tRNS chunk removed.)  However, if you are doing this,
-take great care not to ask for transformations without checking first that
-they apply!
-
-In the first call the background color has the original bit depth and color type
-of the PNG file.  So, for palette images the color is supplied as a palette
-index and for low bit greyscale images the color is a reduced bit value in
-image_background->gray.
-
-If you didn't call png_set_gamma() before reading the file header, for example
-if you need your code to remain compatible with older versions of libpng prior
-to libpng-1.5.4, this is the place to call it.
-
-Do not call it if you called png_set_alpha_mode(); doing so will damage the
-settings put in place by png_set_alpha_mode().  (If png_set_alpha_mode() is
-supported then you can certainly do png_set_gamma() before reading the PNG
-header.)
-
-This API unconditionally sets the screen and file gamma values, so it will
-override the value in the PNG file unless it is called before the PNG file
-reading starts.  For this reason you must always call it with the PNG file
-value when you call it in this position:
-
-   if (png_get_gAMA(png_ptr, info_ptr, &file_gamma))
-      png_set_gamma(png_ptr, screen_gamma, file_gamma);
-
-   else
-      png_set_gamma(png_ptr, screen_gamma, 0.45455);
-
-If you need to reduce an RGB file to a paletted file, or if a paletted
-file has more entries than will fit on your screen, png_set_quantize()
-will do that.  Note that this is a simple match quantization that merely
-finds the closest color available.  This should work fairly well with
-optimized palettes, but fairly badly with linear color cubes.  If you
-pass a palette that is larger than maximum_colors, the file will
-reduce the number of colors in the palette so it will fit into
-maximum_colors.  If there is a histogram, libpng will use it to make
-more intelligent choices when reducing the palette.  If there is no
-histogram, it may not do as good a job.
-
-   if (color_type & PNG_COLOR_MASK_COLOR)
-   {
-      if (png_get_valid(png_ptr, info_ptr,
-          PNG_INFO_PLTE))
-      {
-         png_uint_16p histogram = NULL;
-
-         png_get_hIST(png_ptr, info_ptr,
-             &histogram);
-         png_set_quantize(png_ptr, palette, num_palette,
-            max_screen_colors, histogram, 1);
-      }
-
-      else
-      {
-         png_color std_color_cube[MAX_SCREEN_COLORS] =
-            { ... colors ... };
-
-         png_set_quantize(png_ptr, std_color_cube,
-            MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
-            NULL,0);
-      }
-   }
-
-PNG files describe monochrome as black being zero and white being one.
-The following code will reverse this (make black be one and white be
-zero):
-
-   if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
-      png_set_invert_mono(png_ptr);
-
-This function can also be used to invert grayscale and gray-alpha images:
-
-   if (color_type == PNG_COLOR_TYPE_GRAY ||
-       color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-      png_set_invert_mono(png_ptr);
-
-PNG files store 16-bit pixels in network byte order (big-endian,
-ie. most significant bits first).  This code changes the storage to the
-other way (little-endian, i.e. least significant bits first, the
-way PCs store them):
-
-    if (bit_depth == 16)
-       png_set_swap(png_ptr);
-
-If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
-need to change the order the pixels are packed into bytes, you can use:
-
-    if (bit_depth < 8)
-       png_set_packswap(png_ptr);
-
-Finally, you can write your own transformation function if none of
-the existing ones meets your needs.  This is done by setting a callback
-with
-
-    png_set_read_user_transform_fn(png_ptr,
-        read_transform_fn);
-
-You must supply the function
-
-    void read_transform_fn(png_structp png_ptr, png_row_infop
-        row_info, png_bytep data)
-
-See pngtest.c for a working example.  Your function will be called
-after all of the other transformations have been processed.  Take care with
-interlaced images if you do the interlace yourself - the width of the row is the
-width in 'row_info', not the overall image width.
-
-If supported, libpng provides two information routines that you can use to find
-where you are in processing the image:
-
-   png_get_current_pass_number(png_structp png_ptr);
-   png_get_current_row_number(png_structp png_ptr);
-
-Don't try using these outside a transform callback - firstly they are only
-supported if user transforms are supported, secondly they may well return
-unexpected results unless the row is actually being processed at the moment they
-are called.
-
-With interlaced
-images the value returned is the row in the input sub-image image.  Use
-PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
-find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
-
-The discussion of interlace handling above contains more information on how to
-use these values.
-
-You can also set up a pointer to a user structure for use by your
-callback function, and you can inform libpng that your transform
-function will change the number of channels or bit depth with the
-function
-
-    png_set_user_transform_info(png_ptr, user_ptr,
-        user_depth, user_channels);
-
-The user's application, not libpng, is responsible for allocating and
-freeing any memory required for the user structure.
-
-You can retrieve the pointer via the function
-png_get_user_transform_ptr().  For example:
-
-    voidp read_user_transform_ptr =
-        png_get_user_transform_ptr(png_ptr);
-
-The last thing to handle is interlacing; this is covered in detail below,
-but you must call the function here if you want libpng to handle expansion
-of the interlaced image.
-
-    number_of_passes = png_set_interlace_handling(png_ptr);
-
-After setting the transformations, libpng can update your png_info
-structure to reflect any transformations you've requested with this
-call.
-
-    png_read_update_info(png_ptr, info_ptr);
-
-This is most useful to update the info structure's rowbytes
-field so you can use it to allocate your image memory.  This function
-will also update your palette with the correct screen_gamma and
-background if these have been given with the calls above.  You may
-only call png_read_update_info() once with a particular info_ptr.
-
-After you call png_read_update_info(), you can allocate any
-memory you need to hold the image.  The row data is simply
-raw byte data for all forms of images.  As the actual allocation
-varies among applications, no example will be given.  If you
-are allocating one large chunk, you will need to build an
-array of pointers to each row, as it will be needed for some
-of the functions below.
-
-Be sure that your platform can allocate the buffer that you'll need.
-libpng internally checks for oversize width, but you'll need to
-do your own check for number_of_rows*width*pixel_size if you are using
-a multiple-row buffer:
-
-   /* Guard against integer overflow */
-   if (number_of_rows > PNG_SIZE_MAX/(width*pixel_size)) {
-        png_error(png_ptr,"image_data buffer would be too large");
-   }
-
-Remember: Before you call png_read_update_info(), the png_get_*()
-functions return the values corresponding to the original PNG image.
-After you call png_read_update_info the values refer to the image
-that libpng will output.  Consequently you must call all the png_set_
-functions before you call png_read_update_info().  This is particularly
-important for png_set_interlace_handling() - if you are going to call
-png_read_update_info() you must call png_set_interlace_handling() before
-it unless you want to receive interlaced output.
-
-Reading image data
-
-After you've allocated memory, you can read the image data.
-The simplest way to do this is in one function call.  If you are
-allocating enough memory to hold the whole image, you can just
-call png_read_image() and libpng will read in all the image data
-and put it in the memory area supplied.  You will need to pass in
-an array of pointers to each row.
-
-This function automatically handles interlacing, so you don't
-need to call png_set_interlace_handling() (unless you call
-png_read_update_info()) or call this function multiple times, or any
-of that other stuff necessary with png_read_rows().
-
-   png_read_image(png_ptr, row_pointers);
-
-where row_pointers is:
-
-   png_bytep row_pointers[height];
-
-You can point to void or char or whatever you use for pixels.
-
-If you don't want to read in the whole image at once, you can
-use png_read_rows() instead.  If there is no interlacing (check
-interlace_type == PNG_INTERLACE_NONE), this is simple:
-
-    png_read_rows(png_ptr, row_pointers, NULL,
-        number_of_rows);
-
-where row_pointers is the same as in the png_read_image() call.
-
-If you are doing this just one row at a time, you can do this with
-a single row_pointer instead of an array of row_pointers:
-
-    png_bytep row_pointer = row;
-    png_read_row(png_ptr, row_pointer, NULL);
-
-If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
-get somewhat harder.  The only current (PNG Specification version 1.2)
-interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7);
-a somewhat complicated 2D interlace scheme, known as Adam7, that
-breaks down an image into seven smaller images of varying size, based
-on an 8x8 grid.  This number is defined (from libpng 1.5) as
-PNG_INTERLACE_ADAM7_PASSES in png.h
-
-libpng can fill out those images or it can give them to you "as is".
-It is almost always better to have libpng handle the interlacing for you.
-If you want the images filled out, there are two ways to do that.  The one
-mentioned in the PNG specification is to expand each pixel to cover
-those pixels that have not been read yet (the "rectangle" method).
-This results in a blocky image for the first pass, which gradually
-smooths out as more pixels are read.  The other method is the "sparkle"
-method, where pixels are drawn only in their final locations, with the
-rest of the image remaining whatever colors they were initialized to
-before the start of the read.  The first method usually looks better,
-but tends to be slower, as there are more pixels to put in the rows.
-
-If, as is likely, you want libpng to expand the images, call this before
-calling png_start_read_image() or png_read_update_info():
-
-    if (interlace_type == PNG_INTERLACE_ADAM7)
-       number_of_passes
-           = png_set_interlace_handling(png_ptr);
-
-This will return the number of passes needed.  Currently, this is seven,
-but may change if another interlace type is added.  This function can be
-called even if the file is not interlaced, where it will return one pass.
-You then need to read the whole image 'number_of_passes' times.  Each time
-will distribute the pixels from the current pass to the correct place in
-the output image, so you need to supply the same rows to png_read_rows in
-each pass.
-
-If you are not going to display the image after each pass, but are
-going to wait until the entire image is read in, use the sparkle
-effect.  This effect is faster and the end result of either method
-is exactly the same.  If you are planning on displaying the image
-after each pass, the "rectangle" effect is generally considered the
-better looking one.
-
-If you only want the "sparkle" effect, just call png_read_row() or
-png_read_rows() as
-normal, with the third parameter NULL.  Make sure you make pass over
-the image number_of_passes times, and you don't change the data in the
-rows between calls.  You can change the locations of the data, just
-not the data.  Each pass only writes the pixels appropriate for that
-pass, and assumes the data from previous passes is still valid.
-
-    png_read_rows(png_ptr, row_pointers, NULL,
-        number_of_rows);
-    or
-    png_read_row(png_ptr, row_pointers, NULL);
-
-If you only want the first effect (the rectangles), do the same as
-before except pass the row buffer in the third parameter, and leave
-the second parameter NULL.
-
-    png_read_rows(png_ptr, NULL, row_pointers,
-        number_of_rows);
-    or
-    png_read_row(png_ptr, NULL, row_pointers);
-
-If you don't want libpng to handle the interlacing details, just call
-png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
-Each of the images is a valid image by itself; however, you will almost
-certainly need to distribute the pixels from each sub-image to the
-correct place.  This is where everything gets very tricky.
-
-If you want to retrieve the separate images you must pass the correct
-number of rows to each successive call of png_read_rows().  The calculation
-gets pretty complicated for small images, where some sub-images may
-not even exist because either their width or height ends up zero.
-libpng provides two macros to help you in 1.5 and later versions:
-
-   png_uint_32 width = PNG_PASS_COLS(image_width, pass_number);
-   png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number);
-
-Respectively these tell you the width and height of the sub-image
-corresponding to the numbered pass.  'pass' is in in the range 0 to 6 -
-this can be confusing because the specification refers to the same passes
-as 1 to 7!  Be careful, you must check both the width and height before
-calling png_read_rows() and not call it for that pass if either is zero.
-
-You can, of course, read each sub-image row by row.  If you want to
-produce optimal code to make a pixel-by-pixel transformation of an
-interlaced image this is the best approach; read each row of each pass,
-transform it, and write it out to a new interlaced image.
-
-If you want to de-interlace the image yourself libpng provides further
-macros to help that tell you where to place the pixels in the output image.
-Because the interlacing scheme is rectangular - sub-image pixels are always
-arranged on a rectangular grid - all you need to know for each pass is the
-starting column and row in the output image of the first pixel plus the
-spacing between each pixel.  As of libpng 1.5 there are four macros to
-retrieve this information:
-
-   png_uint_32 x = PNG_PASS_START_COL(pass);
-   png_uint_32 y = PNG_PASS_START_ROW(pass);
-   png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass);
-   png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass);
-
-These allow you to write the obvious loop:
-
-   png_uint_32 input_y = 0;
-   png_uint_32 output_y = PNG_PASS_START_ROW(pass);
-
-   while (output_y < output_image_height)
-   {
-      png_uint_32 input_x = 0;
-      png_uint_32 output_x = PNG_PASS_START_COL(pass);
-
-      while (output_x < output_image_width)
-      {
-         image[output_y][output_x] =
-             subimage[pass][input_y][input_x++];
-
-         output_x += xStep;
-      }
-
-      ++input_y;
-      output_y += yStep;
-   }
-
-Notice that the steps between successive output rows and columns are
-returned as shifts.  This is possible because the pixels in the subimages
-are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original
-image.  In practice you may need to directly calculate the output coordinate
-given an input coordinate.  libpng provides two further macros for this
-purpose:
-
-   png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass);
-   png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass);
-
-Finally a pair of macros are provided to tell you if a particular image
-row or column appears in a given pass:
-
-   int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass);
-   int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass);
-
-Bear in mind that you will probably also need to check the width and height
-of the pass in addition to the above to be sure the pass even exists!
-
-With any luck you are convinced by now that you don't want to do your own
-interlace handling.  In reality normally the only good reason for doing this
-is if you are processing PNG files on a pixel-by-pixel basis and don't want
-to load the whole file into memory when it is interlaced.
-
-libpng includes a test program, pngvalid, that illustrates reading and
-writing of interlaced images.  If you can't get interlacing to work in your
-code and don't want to leave it to libpng (the recommended approach), see
-how pngvalid.c does it.
-
-Finishing a sequential read
-
-After you are finished reading the image through the
-low-level interface, you can finish reading the file.
-
-If you want to use a different crc action for handling CRC errors in
-chunks after the image data, you can call png_set_crc_action()
-again at this point.
-
-If you are interested in comments or time, which may be stored either
-before or after the image data, you should pass the separate png_info
-struct if you want to keep the comments from before and after the image
-separate.
-
-    png_infop end_info = png_create_info_struct(png_ptr);
-
-    if (!end_info)
-    {
-       png_destroy_read_struct(&png_ptr, &info_ptr,
-           (png_infopp)NULL);
-       return (ERROR);
-    }
-
-   png_read_end(png_ptr, end_info);
-
-If you are not interested, you should still call png_read_end()
-but you can pass NULL, avoiding the need to create an end_info structure.
-If you do this, libpng will not process any chunks after IDAT other than
-skipping over them and perhaps (depending on whether you have called
-png_set_crc_action) checking their CRCs while looking for the IEND chunk.
-
-   png_read_end(png_ptr, (png_infop)NULL);
-
-If you don't call png_read_end(), then your file pointer will be
-left pointing to the first chunk after the last IDAT, which is probably
-not what you want if you expect to read something beyond the end of
-the PNG datastream.
-
-When you are done, you can free all memory allocated by libpng like this:
-
-   png_destroy_read_struct(&png_ptr, &info_ptr,
-       &end_info);
-
-or, if you didn't create an end_info structure,
-
-   png_destroy_read_struct(&png_ptr, &info_ptr,
-       (png_infopp)NULL);
-
-It is also possible to individually free the info_ptr members that
-point to libpng-allocated storage with the following function:
-
-    png_free_data(png_ptr, info_ptr, mask, seq)
-
-    mask - identifies data to be freed, a mask
-           containing the bitwise OR of one or
-           more of
-             PNG_FREE_PLTE, PNG_FREE_TRNS,
-             PNG_FREE_HIST, PNG_FREE_ICCP,
-             PNG_FREE_PCAL, PNG_FREE_ROWS,
-             PNG_FREE_SCAL, PNG_FREE_SPLT,
-             PNG_FREE_TEXT, PNG_FREE_UNKN,
-           or simply PNG_FREE_ALL
-
-    seq  - sequence number of item to be freed
-           (-1 for all items)
-
-This function may be safely called when the relevant storage has
-already been freed, or has not yet been allocated, or was allocated
-by the user and not by libpng,  and will in those cases do nothing.
-The "seq" parameter is ignored if only one item of the selected data
-type, such as PLTE, is allowed.  If "seq" is not -1, and multiple items
-are allowed for the data type identified in the mask, such as text or
-sPLT, only the n'th item in the structure is freed, where n is "seq".
-
-The default behavior is only to free data that was allocated internally
-by libpng.  This can be changed, so that libpng will not free the data,
-or so that it will free data that was allocated by the user with png_malloc()
-or png_calloc() and passed in via a png_set_*() function, with
-
-    png_data_freer(png_ptr, info_ptr, freer, mask)
-
-    freer  - one of
-               PNG_DESTROY_WILL_FREE_DATA
-               PNG_SET_WILL_FREE_DATA
-               PNG_USER_WILL_FREE_DATA
-
-    mask   - which data elements are affected
-             same choices as in png_free_data()
-
-This function only affects data that has already been allocated.
-You can call this function after reading the PNG data but before calling
-any png_set_*() functions, to control whether the user or the png_set_*()
-function is responsible for freeing any existing data that might be present,
-and again after the png_set_*() functions to control whether the user
-or png_destroy_*() is supposed to free the data.  When the user assumes
-responsibility for libpng-allocated data, the application must use
-png_free() to free it, and when the user transfers responsibility to libpng
-for data that the user has allocated, the user must have used png_malloc()
-or png_calloc() to allocate it.
-
-If you allocated your row_pointers in a single block, as suggested above in
-the description of the high level read interface, you must not transfer
-responsibility for freeing it to the png_set_rows or png_read_destroy function,
-because they would also try to free the individual row_pointers[i].
-
-If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
-separately, do not transfer responsibility for freeing text_ptr to libpng,
-because when libpng fills a png_text structure it combines these members with
-the key member, and png_free_data() will free only text_ptr.key.  Similarly,
-if you transfer responsibility for free'ing text_ptr from libpng to your
-application, your application must not separately free those members.
-
-The png_free_data() function will turn off the "valid" flag for anything
-it frees.  If you need to turn the flag off for a chunk that was freed by
-your application instead of by libpng, you can use
-
-    png_set_invalid(png_ptr, info_ptr, mask);
-
-    mask - identifies the chunks to be made invalid,
-           containing the bitwise OR of one or
-           more of
-             PNG_INFO_gAMA, PNG_INFO_sBIT,
-             PNG_INFO_cHRM, PNG_INFO_PLTE,
-             PNG_INFO_tRNS, PNG_INFO_bKGD,
-             PNG_INFO_eXIf,
-             PNG_INFO_hIST, PNG_INFO_pHYs,
-             PNG_INFO_oFFs, PNG_INFO_tIME,
-             PNG_INFO_pCAL, PNG_INFO_sRGB,
-             PNG_INFO_iCCP, PNG_INFO_sPLT,
-             PNG_INFO_sCAL, PNG_INFO_IDAT
-
-For a more compact example of reading a PNG image, see the file example.c.
-
-Reading PNG files progressively
-
-The progressive reader is slightly different from the non-progressive
-reader.  Instead of calling png_read_info(), png_read_rows(), and
-png_read_end(), you make one call to png_process_data(), which calls
-callbacks when it has the info, a row, or the end of the image.  You
-set up these callbacks with png_set_progressive_read_fn().  You don't
-have to worry about the input/output functions of libpng, as you are
-giving the library the data directly in png_process_data().  I will
-assume that you have read the section on reading PNG files above,
-so I will only highlight the differences (although I will show
-all of the code).
-
-png_structp png_ptr;
-png_infop info_ptr;
-
- /*  An example code fragment of how you would
-     initialize the progressive reader in your
-     application. */
- int
- initialize_png_reader()
- {
-    png_ptr = png_create_read_struct
-        (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
-         user_error_fn, user_warning_fn);
-
-    if (!png_ptr)
-        return (ERROR);
-
-    info_ptr = png_create_info_struct(png_ptr);
-
-    if (!info_ptr)
-    {
-       png_destroy_read_struct(&png_ptr,
-          (png_infopp)NULL, (png_infopp)NULL);
-       return (ERROR);
-    }
-
-    if (setjmp(png_jmpbuf(png_ptr)))
-    {
-       png_destroy_read_struct(&png_ptr, &info_ptr,
-          (png_infopp)NULL);
-       return (ERROR);
-    }
-
-    /* This one's new.  You can provide functions
-       to be called when the header info is valid,
-       when each row is completed, and when the image
-       is finished.  If you aren't using all functions,
-       you can specify NULL parameters.  Even when all
-       three functions are NULL, you need to call
-       png_set_progressive_read_fn().  You can use
-       any struct as the user_ptr (cast to a void pointer
-       for the function call), and retrieve the pointer
-       from inside the callbacks using the function
-
-          png_get_progressive_ptr(png_ptr);
-
-       which will return a void pointer, which you have
-       to cast appropriately.
-     */
-    png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
-        info_callback, row_callback, end_callback);
-
-    return 0;
- }
-
- /* A code fragment that you call as you receive blocks
-   of data */
- int
- process_data(png_bytep buffer, png_uint_32 length)
- {
-    if (setjmp(png_jmpbuf(png_ptr)))
-    {
-       png_destroy_read_struct(&png_ptr, &info_ptr,
-           (png_infopp)NULL);
-       return (ERROR);
-    }
-
-    /* This one's new also.  Simply give it a chunk
-       of data from the file stream (in order, of
-       course).  On machines with segmented memory
-       models machines, don't give it any more than
-       64K.  The library seems to run fine with sizes
-       of 4K. Although you can give it much less if
-       necessary (I assume you can give it chunks of
-       1 byte, I haven't tried less than 256 bytes
-       yet).  When this function returns, you may
-       want to display any rows that were generated
-       in the row callback if you don't already do
-       so there.
-     */
-    png_process_data(png_ptr, info_ptr, buffer, length);
-
-    /* At this point you can call png_process_data_skip if
-       you want to handle data the library will skip yourself;
-       it simply returns the number of bytes to skip (and stops
-       libpng skipping that number of bytes on the next
-       png_process_data call).
-    return 0;
- }
-
- /* This function is called (as set by
-    png_set_progressive_read_fn() above) when enough data
-    has been supplied so all of the header has been
-    read.
- */
- void
- info_callback(png_structp png_ptr, png_infop info)
- {
-    /* Do any setup here, including setting any of
-       the transformations mentioned in the Reading
-       PNG files section.  For now, you _must_ call
-       either png_start_read_image() or
-       png_read_update_info() after all the
-       transformations are set (even if you don't set
-       any).  You may start getting rows before
-       png_process_data() returns, so this is your
-       last chance to prepare for that.
-
-       This is where you turn on interlace handling,
-       assuming you don't want to do it yourself.
-
-       If you need to you can stop the processing of
-       your original input data at this point by calling
-       png_process_data_pause.  This returns the number
-       of unprocessed bytes from the last png_process_data
-       call - it is up to you to ensure that the next call
-       sees these bytes again.  If you don't want to bother
-       with this you can get libpng to cache the unread
-       bytes by setting the 'save' parameter (see png.h) but
-       then libpng will have to copy the data internally.
-     */
- }
-
- /* This function is called when each row of image
-    data is complete */
- void
- row_callback(png_structp png_ptr, png_bytep new_row,
-    png_uint_32 row_num, int pass)
- {
-    /* If the image is interlaced, and you turned
-       on the interlace handler, this function will
-       be called for every row in every pass.  Some
-       of these rows will not be changed from the
-       previous pass.  When the row is not changed,
-       the new_row variable will be NULL.  The rows
-       and passes are called in order, so you don't
-       really need the row_num and pass, but I'm
-       supplying them because it may make your life
-       easier.
-
-       If you did not turn on interlace handling then
-       the callback is called for each row of each
-       sub-image when the image is interlaced.  In this
-       case 'row_num' is the row in the sub-image, not
-       the row in the output image as it is in all other
-       cases.
-
-       For the non-NULL rows of interlaced images when
-       you have switched on libpng interlace handling,
-       you must call png_progressive_combine_row()
-       passing in the row and the old row.  You can
-       call this function for NULL rows (it will just
-       return) and for non-interlaced images (it just
-       does the memcpy for you) if it will make the
-       code easier.  Thus, you can just do this for
-       all cases if you switch on interlace handling;
-     */
-
-        png_progressive_combine_row(png_ptr, old_row,
-          new_row);
-
-    /* where old_row is what was displayed
-       previously for the row.  Note that the first
-       pass (pass == 0, really) will completely cover
-       the old row, so the rows do not have to be
-       initialized.  After the first pass (and only
-       for interlaced images), you will have to pass
-       the current row, and the function will combine
-       the old row and the new row.
-
-       You can also call png_process_data_pause in this
-       callback - see above.
-    */
- }
-
- void
- end_callback(png_structp png_ptr, png_infop info)
- {
-    /* This function is called after the whole image
-       has been read, including any chunks after the
-       image (up to and including the IEND).  You
-       will usually have the same info chunk as you
-       had in the header, although some data may have
-       been added to the comments and time fields.
-
-       Most people won't do much here, perhaps setting
-       a flag that marks the image as finished.
-     */
- }
-
-
-
-IV. Writing
-
-Much of this is very similar to reading.  However, everything of
-importance is repeated here, so you won't have to constantly look
-back up in the reading section to understand writing.
-
-Setup
-
-You will want to do the I/O initialization before you get into libpng,
-so if it doesn't work, you don't have anything to undo. If you are not
-using the standard I/O functions, you will need to replace them with
-custom writing functions.  See the discussion under Customizing libpng.
-
-    FILE *fp = fopen(file_name, "wb");
-
-    if (!fp)
-       return (ERROR);
-
-Next, png_struct and png_info need to be allocated and initialized.
-As these can be both relatively large, you may not want to store these
-on the stack, unless you have stack space to spare.  Of course, you
-will want to check if they return NULL.  If you are also reading,
-you won't want to name your read structure and your write structure
-both "png_ptr"; you can call them anything you like, such as
-"read_ptr" and "write_ptr".  Look at pngtest.c, for example.
-
-    png_structp png_ptr = png_create_write_struct
-       (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
-        user_error_fn, user_warning_fn);
-
-    if (!png_ptr)
-       return (ERROR);
-
-    png_infop info_ptr = png_create_info_struct(png_ptr);
-    if (!info_ptr)
-    {
-       png_destroy_write_struct(&png_ptr,
-           (png_infopp)NULL);
-       return (ERROR);
-    }
-
-If you want to use your own memory allocation routines,
-define PNG_USER_MEM_SUPPORTED and use
-png_create_write_struct_2() instead of png_create_write_struct():
-
-    png_structp png_ptr = png_create_write_struct_2
-       (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
-        user_error_fn, user_warning_fn, (png_voidp)
-        user_mem_ptr, user_malloc_fn, user_free_fn);
-
-After you have these structures, you will need to set up the
-error handling.  When libpng encounters an error, it expects to
-longjmp() back to your routine.  Therefore, you will need to call
-setjmp() and pass the png_jmpbuf(png_ptr).  If you
-write the file from different routines, you will need to update
-the png_jmpbuf(png_ptr) every time you enter a new routine that will
-call a png_*() function.  See your documentation of setjmp/longjmp
-for your compiler for more information on setjmp/longjmp.  See
-the discussion on libpng error handling in the Customizing Libpng
-section below for more information on the libpng error handling.
-
-    if (setjmp(png_jmpbuf(png_ptr)))
-    {
-    png_destroy_write_struct(&png_ptr, &info_ptr);
-       fclose(fp);
-       return (ERROR);
-    }
-    ...
-    return;
-
-If you would rather avoid the complexity of setjmp/longjmp issues,
-you can compile libpng with PNG_NO_SETJMP, in which case
-errors will result in a call to PNG_ABORT() which defaults to abort().
-
-You can #define PNG_ABORT() to a function that does something
-more useful than abort(), as long as your function does not
-return.
-
-Checking for invalid palette index on write was added at libpng
-1.5.10.  If a pixel contains an invalid (out-of-range) index libpng issues
-a benign error.  This is enabled by default because this condition is an
-error according to the PNG specification, Clause 11.3.2, but the error can
-be ignored in each png_ptr with
-
-   png_set_check_for_invalid_index(png_ptr, 0);
-
-If the error is ignored, or if png_benign_error() treats it as a warning,
-any invalid pixels are written as-is by the encoder, resulting in an
-invalid PNG datastream as output.  In this case the application is
-responsible for ensuring that the pixel indexes are in range when it writes
-a PLTE chunk with fewer entries than the bit depth would allow.
-
-Now you need to set up the output code.  The default for libpng is to
-use the C function fwrite().  If you use this, you will need to pass a
-valid FILE * in the function png_init_io().  Be sure that the file is
-opened in binary mode.  Again, if you wish to handle writing data in
-another way, see the discussion on libpng I/O handling in the Customizing
-Libpng section below.
-
-    png_init_io(png_ptr, fp);
-
-If you are embedding your PNG into a datastream such as MNG, and don't
-want libpng to write the 8-byte signature, or if you have already
-written the signature in your application, use
-
-    png_set_sig_bytes(png_ptr, 8);
-
-to inform libpng that it should not write a signature.
-
-Write callbacks
-
-At this point, you can set up a callback function that will be
-called after each row has been written, which you can use to control
-a progress meter or the like.  It's demonstrated in pngtest.c.
-You must supply a function
-
-    void write_row_callback(png_structp png_ptr, png_uint_32 row,
-       int pass);
-    {
-      /* put your code here */
-    }
-
-(You can give it another name that you like instead of "write_row_callback")
-
-To inform libpng about your function, use
-
-    png_set_write_status_fn(png_ptr, write_row_callback);
-
-When this function is called the row has already been completely processed and
-it has also been written out.  The 'row' and 'pass' refer to the next row to be
-handled.  For the
-non-interlaced case the row that was just handled is simply one less than the
-passed in row number, and pass will always be 0.  For the interlaced case the
-same applies unless the row value is 0, in which case the row just handled was
-the last one from one of the preceding passes.  Because interlacing may skip a
-pass you cannot be sure that the preceding pass is just 'pass-1', if you really
-need to know what the last pass is record (row,pass) from the callback and use
-the last recorded value each time.
-
-As with the user transform you can find the output row using the
-PNG_ROW_FROM_PASS_ROW macro.
-
-You now have the option of modifying how the compression library will
-run.  The following functions are mainly for testing, but may be useful
-in some cases, like if you need to write PNG files extremely fast and
-are willing to give up some compression, or if you want to get the
-maximum possible compression at the expense of slower writing.  If you
-have no special needs in this area, let the library do what it wants by
-not calling this function at all, as it has been tuned to deliver a good
-speed/compression ratio. The second parameter to png_set_filter() is
-the filter method, for which the only valid values are 0 (as of the
-July 1999 PNG specification, version 1.2) or 64 (if you are writing
-a PNG datastream that is to be embedded in a MNG datastream).  The third
-parameter is a flag that indicates which filter type(s) are to be tested
-for each scanline.  See the PNG specification for details on the specific
-filter types.
-
-
-    /* turn on or off filtering, and/or choose
-       specific filters.  You can use either a single
-       PNG_FILTER_VALUE_NAME or the bitwise OR of one
-       or more PNG_FILTER_NAME masks.
-     */
-    png_set_filter(png_ptr, 0,
-       PNG_FILTER_NONE  | PNG_FILTER_VALUE_NONE |
-       PNG_FILTER_SUB   | PNG_FILTER_VALUE_SUB  |
-       PNG_FILTER_UP    | PNG_FILTER_VALUE_UP   |
-       PNG_FILTER_AVG   | PNG_FILTER_VALUE_AVG  |
-       PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
-       PNG_ALL_FILTERS  | PNG_FAST_FILTERS);
-
-If an application wants to start and stop using particular filters during
-compression, it should start out with all of the filters (to ensure that
-the previous row of pixels will be stored in case it's needed later),
-and then add and remove them after the start of compression.
-
-If you are writing a PNG datastream that is to be embedded in a MNG
-datastream, the second parameter can be either 0 or 64.
-
-The png_set_compression_*() functions interface to the zlib compression
-library, and should mostly be ignored unless you really know what you are
-doing.  The only generally useful call is png_set_compression_level()
-which changes how much time zlib spends on trying to compress the image
-data.  See the Compression Library (zlib.h and algorithm.txt, distributed
-with zlib) for details on the compression levels.
-
-    #include zlib.h
-
-    /* Set the zlib compression level */
-    png_set_compression_level(png_ptr,
-        Z_BEST_COMPRESSION);
-
-    /* Set other zlib parameters for compressing IDAT */
-    png_set_compression_mem_level(png_ptr, 8);
-    png_set_compression_strategy(png_ptr,
-        Z_DEFAULT_STRATEGY);
-    png_set_compression_window_bits(png_ptr, 15);
-    png_set_compression_method(png_ptr, 8);
-    png_set_compression_buffer_size(png_ptr, 8192)
-
-    /* Set zlib parameters for text compression
-     * If you don't call these, the parameters
-     * fall back on those defined for IDAT chunks
-     */
-    png_set_text_compression_mem_level(png_ptr, 8);
-    png_set_text_compression_strategy(png_ptr,
-        Z_DEFAULT_STRATEGY);
-    png_set_text_compression_window_bits(png_ptr, 15);
-    png_set_text_compression_method(png_ptr, 8);
-
-Setting the contents of info for output
-
-You now need to fill in the png_info structure with all the data you
-wish to write before the actual image.  Note that the only thing you
-are allowed to write after the image is the text chunks and the time
-chunk (as of PNG Specification 1.2, anyway).  See png_write_end() and
-the latest PNG specification for more information on that.  If you
-wish to write them before the image, fill them in now, and flag that
-data as being valid.  If you want to wait until after the data, don't
-fill them until png_write_end().  For all the fields in png_info and
-their data types, see png.h.  For explanations of what the fields
-contain, see the PNG specification.
-
-Some of the more important parts of the png_info are:
-
-    png_set_IHDR(png_ptr, info_ptr, width, height,
-       bit_depth, color_type, interlace_type,
-       compression_type, filter_method)
-
-    width          - holds the width of the image
-                     in pixels (up to 2^31).
-
-    height         - holds the height of the image
-                     in pixels (up to 2^31).
-
-    bit_depth      - holds the bit depth of one of the
-                     image channels.
-                     (valid values are 1, 2, 4, 8, 16
-                     and depend also on the
-                     color_type.  See also significant
-                     bits (sBIT) below).
-
-    color_type     - describes which color/alpha
-                     channels are present.
-                     PNG_COLOR_TYPE_GRAY
-                        (bit depths 1, 2, 4, 8, 16)
-                     PNG_COLOR_TYPE_GRAY_ALPHA
-                        (bit depths 8, 16)
-                     PNG_COLOR_TYPE_PALETTE
-                        (bit depths 1, 2, 4, 8)
-                     PNG_COLOR_TYPE_RGB
-                        (bit_depths 8, 16)
-                     PNG_COLOR_TYPE_RGB_ALPHA
-                        (bit_depths 8, 16)
-
-                     PNG_COLOR_MASK_PALETTE
-                     PNG_COLOR_MASK_COLOR
-                     PNG_COLOR_MASK_ALPHA
-
-    interlace_type - PNG_INTERLACE_NONE or
-                     PNG_INTERLACE_ADAM7
-
-    compression_type - (must be
-                     PNG_COMPRESSION_TYPE_DEFAULT)
-
-    filter_method  - (must be PNG_FILTER_TYPE_DEFAULT
-                     or, if you are writing a PNG to
-                     be embedded in a MNG datastream,
-                     can also be
-                     PNG_INTRAPIXEL_DIFFERENCING)
-
-If you call png_set_IHDR(), the call must appear before any of the
-other png_set_*() functions, because they might require access to some of
-the IHDR settings.  The remaining png_set_*() functions can be called
-in any order.
-
-If you wish, you can reset the compression_type, interlace_type, or
-filter_method later by calling png_set_IHDR() again; if you do this, the
-width, height, bit_depth, and color_type must be the same in each call.
-
-    png_set_PLTE(png_ptr, info_ptr, palette,
-       num_palette);
-
-    palette        - the palette for the file
-                     (array of png_color)
-    num_palette    - number of entries in the palette
-
-
-    png_set_gAMA(png_ptr, info_ptr, file_gamma);
-    png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma);
-
-    file_gamma     - the gamma at which the image was
-                     created (PNG_INFO_gAMA)
-
-    int_file_gamma - 100,000 times the gamma at which
-                     the image was created
-
-    png_set_cHRM(png_ptr, info_ptr,  white_x, white_y, red_x, red_y,
-                     green_x, green_y, blue_x, blue_y)
-    png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X,
-                     green_Y, green_Z, blue_X, blue_Y, blue_Z)
-    png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y,
-                     int_red_x, int_red_y, int_green_x, int_green_y,
-                     int_blue_x, int_blue_y)
-    png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y,
-                     int_red_Z, int_green_X, int_green_Y, int_green_Z,
-                     int_blue_X, int_blue_Y, int_blue_Z)
-
-    {white,red,green,blue}_{x,y}
-                     A color space encoding specified using the chromaticities
-                     of the end points and the white point.
-
-    {red,green,blue}_{X,Y,Z}
-                     A color space encoding specified using the encoding end
-                     points - the CIE tristimulus specification of the intended
-                     color of the red, green and blue channels in the PNG RGB
-                     data.  The white point is simply the sum of the three end
-                     points.
-
-    png_set_sRGB(png_ptr, info_ptr, srgb_intent);
-
-    srgb_intent    - the rendering intent
-                     (PNG_INFO_sRGB) The presence of
-                     the sRGB chunk means that the pixel
-                     data is in the sRGB color space.
-                     This chunk also implies specific
-                     values of gAMA and cHRM.  Rendering
-                     intent is the CSS-1 property that
-                     has been defined by the International
-                     Color Consortium
-                     (http://www.color.org).
-                     It can be one of
-                     PNG_sRGB_INTENT_SATURATION,
-                     PNG_sRGB_INTENT_PERCEPTUAL,
-                     PNG_sRGB_INTENT_ABSOLUTE, or
-                     PNG_sRGB_INTENT_RELATIVE.
-
-
-    png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
-       srgb_intent);
-
-    srgb_intent    - the rendering intent
-                     (PNG_INFO_sRGB) The presence of the
-                     sRGB chunk means that the pixel
-                     data is in the sRGB color space.
-                     This function also causes gAMA and
-                     cHRM chunks with the specific values
-                     that are consistent with sRGB to be
-                     written.
-
-    png_set_iCCP(png_ptr, info_ptr, name, compression_type,
-                       profile, proflen);
-
-    name             - The profile name.
-
-    compression_type - The compression type; always
-                       PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
-                       You may give NULL to this argument to
-                       ignore it.
-
-    profile          - International Color Consortium color
-                       profile data. May contain NULs.
-
-    proflen          - length of profile data in bytes.
-
-    png_set_sBIT(png_ptr, info_ptr, sig_bit);
-
-    sig_bit        - the number of significant bits for
-                     (PNG_INFO_sBIT) each of the gray, red,
-                     green, and blue channels, whichever are
-                     appropriate for the given color type
-                     (png_color_16)
-
-    png_set_tRNS(png_ptr, info_ptr, trans_alpha,
-       num_trans, trans_color);
-
-    trans_alpha    - array of alpha (transparency)
-                     entries for palette (PNG_INFO_tRNS)
-
-    num_trans      - number of transparent entries
-                     (PNG_INFO_tRNS)
-
-    trans_color    - graylevel or color sample values
-                     (in order red, green, blue) of the
-                     single transparent color for
-                     non-paletted images (PNG_INFO_tRNS)
-
-    png_set_eXIf_1(png_ptr, info_ptr, num_exif, exif);
-
-    exif           - Exif profile (array of
-                     png_byte) (PNG_INFO_eXIf)
-
-    png_set_hIST(png_ptr, info_ptr, hist);
-
-    hist           - histogram of palette (array of
-                     png_uint_16) (PNG_INFO_hIST)
-
-    png_set_tIME(png_ptr, info_ptr, mod_time);
-
-    mod_time       - time image was last modified
-                     (PNG_VALID_tIME)
-
-    png_set_bKGD(png_ptr, info_ptr, background);
-
-    background     - background color (of type
-                     png_color_16p) (PNG_VALID_bKGD)
-
-    png_set_text(png_ptr, info_ptr, text_ptr, num_text);
-
-    text_ptr       - array of png_text holding image
-                     comments
-
-    text_ptr[i].compression - type of compression used
-                 on "text" PNG_TEXT_COMPRESSION_NONE
-                           PNG_TEXT_COMPRESSION_zTXt
-                           PNG_ITXT_COMPRESSION_NONE
-                           PNG_ITXT_COMPRESSION_zTXt
-    text_ptr[i].key   - keyword for comment.  Must contain
-                 1-79 characters.
-    text_ptr[i].text  - text comments for current
-                         keyword.  Can be NULL or empty.
-    text_ptr[i].text_length - length of text string,
-                 after decompression, 0 for iTXt
-    text_ptr[i].itxt_length - length of itxt string,
-                 after decompression, 0 for tEXt/zTXt
-    text_ptr[i].lang  - language of comment (NULL or
-                         empty for unknown).
-    text_ptr[i].translated_keyword  - keyword in UTF-8 (NULL
-                         or empty for unknown).
-
-    Note that the itxt_length, lang, and lang_key
-    members of the text_ptr structure only exist when the
-    library is built with iTXt chunk support.  Prior to
-    libpng-1.4.0 the library was built by default without
-    iTXt support. Also note that when iTXt is supported,
-    they contain NULL pointers when the "compression"
-    field contains PNG_TEXT_COMPRESSION_NONE or
-    PNG_TEXT_COMPRESSION_zTXt.
-
-    num_text       - number of comments
-
-    png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
-       num_spalettes);
-
-    palette_ptr    - array of png_sPLT_struct structures
-                     to be added to the list of palettes
-                     in the info structure.
-    num_spalettes  - number of palette structures to be
-                     added.
-
-    png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
-        unit_type);
-
-    offset_x  - positive offset from the left
-                     edge of the screen
-
-    offset_y  - positive offset from the top
-                     edge of the screen
-
-    unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
-
-    png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
-        unit_type);
-
-    res_x       - pixels/unit physical resolution
-                  in x direction
-
-    res_y       - pixels/unit physical resolution
-                  in y direction
-
-    unit_type   - PNG_RESOLUTION_UNKNOWN,
-                  PNG_RESOLUTION_METER
-
-    png_set_sCAL(png_ptr, info_ptr, unit, width, height)
-
-    unit        - physical scale units (an integer)
-
-    width       - width of a pixel in physical scale units
-
-    height      - height of a pixel in physical scale units
-                  (width and height are doubles)
-
-    png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
-
-    unit        - physical scale units (an integer)
-
-    width       - width of a pixel in physical scale units
-                  expressed as a string
-
-    height      - height of a pixel in physical scale units
-                 (width and height are strings like "2.54")
-
-    png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
-       num_unknowns)
-
-    unknowns          - array of png_unknown_chunk
-                        structures holding unknown chunks
-    unknowns[i].name  - name of unknown chunk
-    unknowns[i].data  - data of unknown chunk
-    unknowns[i].size  - size of unknown chunk's data
-    unknowns[i].location - position to write chunk in file
-                           0: do not write chunk
-                           PNG_HAVE_IHDR: before PLTE
-                           PNG_HAVE_PLTE: before IDAT
-                           PNG_AFTER_IDAT: after IDAT
-
-The "location" member is set automatically according to
-what part of the output file has already been written.
-You can change its value after calling png_set_unknown_chunks()
-as demonstrated in pngtest.c.  Within each of the "locations",
-the chunks are sequenced according to their position in the
-structure (that is, the value of "i", which is the order in which
-the chunk was either read from the input file or defined with
-png_set_unknown_chunks).
-
-A quick word about text and num_text.  text is an array of png_text
-structures.  num_text is the number of valid structures in the array.
-Each png_text structure holds a language code, a keyword, a text value,
-and a compression type.
-
-The compression types have the same valid numbers as the compression
-types of the image data.  Currently, the only valid number is zero.
-However, you can store text either compressed or uncompressed, unlike
-images, which always have to be compressed.  So if you don't want the
-text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
-Because tEXt and zTXt chunks don't have a language field, if you
-specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
-any language code or translated keyword will not be written out.
-
-Until text gets around a few hundred bytes, it is not worth compressing it.
-After the text has been written out to the file, the compression type
-is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
-so that it isn't written out again at the end (in case you are calling
-png_write_end() with the same struct).
-
-The keywords that are given in the PNG Specification are:
-
-    Title            Short (one line) title or
-                     caption for image
-
-    Author           Name of image's creator
-
-    Description      Description of image (possibly long)
-
-    Copyright        Copyright notice
-
-    Creation Time    Time of original image creation
-                     (usually RFC 1123 format, see below)
-
-    Software         Software used to create the image
-
-    Disclaimer       Legal disclaimer
-
-    Warning          Warning of nature of content
-
-    Source           Device used to create the image
-
-    Comment          Miscellaneous comment; conversion
-                     from other image format
-
-The keyword-text pairs work like this.  Keywords should be short
-simple descriptions of what the comment is about.  Some typical
-keywords are found in the PNG specification, as is some recommendations
-on keywords.  You can repeat keywords in a file.  You can even write
-some text before the image and some after.  For example, you may want
-to put a description of the image before the image, but leave the
-disclaimer until after, so viewers working over modem connections
-don't have to wait for the disclaimer to go over the modem before
-they start seeing the image.  Finally, keywords should be full
-words, not abbreviations.  Keywords and text are in the ISO 8859-1
-(Latin-1) character set (a superset of regular ASCII) and can not
-contain NUL characters, and should not contain control or other
-unprintable characters.  To make the comments widely readable, stick
-with basic ASCII, and avoid machine specific character set extensions
-like the IBM-PC character set.  The keyword must be present, but
-you can leave off the text string on non-compressed pairs.
-Compressed pairs must have a text string, as only the text string
-is compressed anyway, so the compression would be meaningless.
-
-PNG supports modification time via the png_time structure.  Two
-conversion routines are provided, png_convert_from_time_t() for
-time_t and png_convert_from_struct_tm() for struct tm.  The
-time_t routine uses gmtime().  You don't have to use either of
-these, but if you wish to fill in the png_time structure directly,
-you should provide the time in universal time (GMT) if possible
-instead of your local time.  Note that the year number is the full
-year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
-that months start with 1.
-
-If you want to store the time of the original image creation, you should
-use a plain tEXt chunk with the "Creation Time" keyword.  This is
-necessary because the "creation time" of a PNG image is somewhat vague,
-depending on whether you mean the PNG file, the time the image was
-created in a non-PNG format, a still photo from which the image was
-scanned, or possibly the subject matter itself.  In order to facilitate
-machine-readable dates, it is recommended that the "Creation Time"
-tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
-although this isn't a requirement.  Unlike the tIME chunk, the
-"Creation Time" tEXt chunk is not expected to be automatically changed
-by the software.  To facilitate the use of RFC 1123 dates, a function
-png_convert_to_rfc1123_buffer(buffer, png_timep) is provided to
-convert from PNG time to an RFC 1123 format string.  The caller must provide
-a writeable buffer of at least 29 bytes.
-
-Writing unknown chunks
-
-You can use the png_set_unknown_chunks function to queue up private chunks
-for writing.  You give it a chunk name, location, raw data, and a size.  You
-also must use png_set_keep_unknown_chunks() to ensure that libpng will
-handle them.  That's all there is to it.  The chunks will be written by the
-next following png_write_info_before_PLTE, png_write_info, or png_write_end
-function, depending upon the specified location.  Any chunks previously
-read into the info structure's unknown-chunk list will also be written out
-in a sequence that satisfies the PNG specification's ordering rules.
-
-Here is an example of writing two private chunks, prVt and miNE:
-
-    #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
-    /* Set unknown chunk data */
-    png_unknown_chunk unk_chunk[2];
-    strcpy((char *) unk_chunk[0].name, "prVt";
-    unk_chunk[0].data = (unsigned char *) "PRIVATE DATA";
-    unk_chunk[0].size = strlen(unk_chunk[0].data)+1;
-    unk_chunk[0].location = PNG_HAVE_IHDR;
-    strcpy((char *) unk_chunk[1].name, "miNE";
-    unk_chunk[1].data = (unsigned char *) "MY CHUNK DATA";
-    unk_chunk[1].size = strlen(unk_chunk[0].data)+1;
-    unk_chunk[1].location = PNG_AFTER_IDAT;
-    png_set_unknown_chunks(write_ptr, write_info_ptr,
-        unk_chunk, 2);
-    /* Needed because miNE is not safe-to-copy */
-    png_set_keep_unknown_chunks(png, PNG_HANDLE_CHUNK_ALWAYS,
-       (png_bytep) "miNE", 1);
-    # if PNG_LIBPNG_VER < 10600
-      /* Deal with unknown chunk location bug in 1.5.x and earlier */
-      png_set_unknown_chunk_location(png, info, 0, PNG_HAVE_IHDR);
-      png_set_unknown_chunk_location(png, info, 1, PNG_AFTER_IDAT);
-    # endif
-    # if PNG_LIBPNG_VER < 10500
-      /* PNG_AFTER_IDAT writes two copies of the chunk prior to libpng-1.5.0,
-       * one before IDAT and another after IDAT, so don't use it; only use
-       * PNG_HAVE_IHDR location.  This call resets the location previously
-       * set by assignment and png_set_unknown_chunk_location() for chunk 1.
-       */
-      png_set_unknown_chunk_location(png, info, 1, PNG_HAVE_IHDR);
-    # endif
-    #endif
-
-The high-level write interface
-
-At this point there are two ways to proceed; through the high-level
-write interface, or through a sequence of low-level write operations.
-You can use the high-level interface if your image data is present
-in the info structure.  All defined output
-transformations are permitted, enabled by the following masks.
-
-    PNG_TRANSFORM_IDENTITY      No transformation
-    PNG_TRANSFORM_PACKING       Pack 1, 2 and 4-bit samples
-    PNG_TRANSFORM_PACKSWAP      Change order of packed
-                                pixels to LSB first
-    PNG_TRANSFORM_INVERT_MONO   Invert monochrome images
-    PNG_TRANSFORM_SHIFT         Normalize pixels to the
-                                sBIT depth
-    PNG_TRANSFORM_BGR           Flip RGB to BGR, RGBA
-                                to BGRA
-    PNG_TRANSFORM_SWAP_ALPHA    Flip RGBA to ARGB or GA
-                                to AG
-    PNG_TRANSFORM_INVERT_ALPHA  Change alpha from opacity
-                                to transparency
-    PNG_TRANSFORM_SWAP_ENDIAN   Byte-swap 16-bit samples
-    PNG_TRANSFORM_STRIP_FILLER        Strip out filler
-                                      bytes (deprecated).
-    PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading
-                                      filler bytes
-    PNG_TRANSFORM_STRIP_FILLER_AFTER  Strip out trailing
-                                      filler bytes
-
-If you have valid image data in the info structure (you can use
-png_set_rows() to put image data in the info structure), simply do this:
-
-    png_write_png(png_ptr, info_ptr, png_transforms, NULL)
-
-where png_transforms is an integer containing the bitwise OR of some set of
-transformation flags.  This call is equivalent to png_write_info(),
-followed the set of transformations indicated by the transform mask,
-then png_write_image(), and finally png_write_end().
-
-(The final parameter of this call is not yet used.  Someday it might point
-to transformation parameters required by some future output transform.)
-
-You must use png_transforms and not call any png_set_transform() functions
-when you use png_write_png().
-
-The low-level write interface
-
-If you are going the low-level route instead, you are now ready to
-write all the file information up to the actual image data.  You do
-this with a call to png_write_info().
-
-    png_write_info(png_ptr, info_ptr);
-
-Note that there is one transformation you may need to do before
-png_write_info().  In PNG files, the alpha channel in an image is the
-level of opacity.  If your data is supplied as a level of transparency,
-you can invert the alpha channel before you write it, so that 0 is
-fully transparent and 255 (in 8-bit or paletted images) or 65535
-(in 16-bit images) is fully opaque, with
-
-    png_set_invert_alpha(png_ptr);
-
-This must appear before png_write_info() instead of later with the
-other transformations because in the case of paletted images the tRNS
-chunk data has to be inverted before the tRNS chunk is written.  If
-your image is not a paletted image, the tRNS data (which in such cases
-represents a single color to be rendered as transparent) won't need to
-be changed, and you can safely do this transformation after your
-png_write_info() call.
-
-If you need to write a private chunk that you want to appear before
-the PLTE chunk when PLTE is present, you can write the PNG info in
-two steps, and insert code to write your own chunk between them:
-
-    png_write_info_before_PLTE(png_ptr, info_ptr);
-    png_set_unknown_chunks(png_ptr, info_ptr, ...);
-    png_write_info(png_ptr, info_ptr);
-
-After you've written the file information, you can set up the library
-to handle any special transformations of the image data.  The various
-ways to transform the data will be described in the order that they
-should occur.  This is important, as some of these change the color
-type and/or bit depth of the data, and some others only work on
-certain color types and bit depths.  Even though each transformation
-checks to see if it has data that it can do something with, you should
-make sure to only enable a transformation if it will be valid for the
-data.  For example, don't swap red and blue on grayscale data.
-
-PNG files store RGB pixels packed into 3 or 6 bytes.  This code tells
-the library to strip input data that has 4 or 8 bytes per pixel down
-to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
-bytes per pixel).
-
-    png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
-
-where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
-PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
-is stored XRGB or RGBX.
-
-PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
-they can, resulting in, for example, 8 pixels per byte for 1 bit files.
-If the data is supplied at 1 pixel per byte, use this code, which will
-correctly pack the pixels into a single byte:
-
-    png_set_packing(png_ptr);
-
-PNG files reduce possible bit depths to 1, 2, 4, 8, and 16.  If your
-data is of another bit depth, you can write an sBIT chunk into the
-file so that decoders can recover the original data if desired.
-
-    /* Set the true bit depth of the image data */
-    if (color_type & PNG_COLOR_MASK_COLOR)
-    {
-       sig_bit.red = true_bit_depth;
-       sig_bit.green = true_bit_depth;
-       sig_bit.blue = true_bit_depth;
-    }
-
-    else
-    {
-       sig_bit.gray = true_bit_depth;
-    }
-
-    if (color_type & PNG_COLOR_MASK_ALPHA)
-    {
-       sig_bit.alpha = true_bit_depth;
-    }
-
-    png_set_sBIT(png_ptr, info_ptr, &sig_bit);
-
-If the data is stored in the row buffer in a bit depth other than
-one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG),
-this will scale the values to appear to be the correct bit depth as
-is required by PNG.
-
-    png_set_shift(png_ptr, &sig_bit);
-
-PNG files store 16-bit pixels in network byte order (big-endian,
-ie. most significant bits first).  This code would be used if they are
-supplied the other way (little-endian, i.e. least significant bits
-first, the way PCs store them):
-
-    if (bit_depth > 8)
-       png_set_swap(png_ptr);
-
-If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
-need to change the order the pixels are packed into bytes, you can use:
-
-    if (bit_depth < 8)
-       png_set_packswap(png_ptr);
-
-PNG files store 3 color pixels in red, green, blue order.  This code
-would be used if they are supplied as blue, green, red:
-
-    png_set_bgr(png_ptr);
-
-PNG files describe monochrome as black being zero and white being
-one. This code would be used if the pixels are supplied with this reversed
-(black being one and white being zero):
-
-    png_set_invert_mono(png_ptr);
-
-Finally, you can write your own transformation function if none of
-the existing ones meets your needs.  This is done by setting a callback
-with
-
-    png_set_write_user_transform_fn(png_ptr,
-       write_transform_fn);
-
-You must supply the function
-
-    void write_transform_fn(png_structp png_ptr, png_row_infop
-       row_info, png_bytep data)
-
-See pngtest.c for a working example.  Your function will be called
-before any of the other transformations are processed.  If supported
-libpng also supplies an information routine that may be called from
-your callback:
-
-   png_get_current_row_number(png_ptr);
-   png_get_current_pass_number(png_ptr);
-
-This returns the current row passed to the transform.  With interlaced
-images the value returned is the row in the input sub-image image.  Use
-PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
-find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
-
-The discussion of interlace handling above contains more information on how to
-use these values.
-
-You can also set up a pointer to a user structure for use by your
-callback function.
-
-    png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
-
-The user_channels and user_depth parameters of this function are ignored
-when writing; you can set them to zero as shown.
-
-You can retrieve the pointer via the function png_get_user_transform_ptr().
-For example:
-
-    voidp write_user_transform_ptr =
-       png_get_user_transform_ptr(png_ptr);
-
-It is possible to have libpng flush any pending output, either manually,
-or automatically after a certain number of lines have been written.  To
-flush the output stream a single time call:
-
-    png_write_flush(png_ptr);
-
-and to have libpng flush the output stream periodically after a certain
-number of scanlines have been written, call:
-
-    png_set_flush(png_ptr, nrows);
-
-Note that the distance between rows is from the last time png_write_flush()
-was called, or the first row of the image if it has never been called.
-So if you write 50 lines, and then png_set_flush 25, it will flush the
-output on the next scanline, and every 25 lines thereafter, unless
-png_write_flush() is called before 25 more lines have been written.
-If nrows is too small (less than about 10 lines for a 640 pixel wide
-RGB image) the image compression may decrease noticeably (although this
-may be acceptable for real-time applications).  Infrequent flushing will
-only degrade the compression performance by a few percent over images
-that do not use flushing.
-
-Writing the image data
-
-That's it for the transformations.  Now you can write the image data.
-The simplest way to do this is in one function call.  If you have the
-whole image in memory, you can just call png_write_image() and libpng
-will write the image.  You will need to pass in an array of pointers to
-each row.  This function automatically handles interlacing, so you don't
-need to call png_set_interlace_handling() or call this function multiple
-times, or any of that other stuff necessary with png_write_rows().
-
-    png_write_image(png_ptr, row_pointers);
-
-where row_pointers is:
-
-    png_byte *row_pointers[height];
-
-You can point to void or char or whatever you use for pixels.
-
-If you don't want to write the whole image at once, you can
-use png_write_rows() instead.  If the file is not interlaced,
-this is simple:
-
-    png_write_rows(png_ptr, row_pointers,
-       number_of_rows);
-
-row_pointers is the same as in the png_write_image() call.
-
-If you are just writing one row at a time, you can do this with
-a single row_pointer instead of an array of row_pointers:
-
-    png_bytep row_pointer = row;
-
-    png_write_row(png_ptr, row_pointer);
-
-When the file is interlaced, things can get a good deal more complicated.
-The only currently (as of the PNG Specification version 1.2, dated July
-1999) defined interlacing scheme for PNG files is the "Adam7" interlace
-scheme, that breaks down an image into seven smaller images of varying
-size.  libpng will build these images for you, or you can do them
-yourself.  If you want to build them yourself, see the PNG specification
-for details of which pixels to write when.
-
-If you don't want libpng to handle the interlacing details, just
-use png_set_interlace_handling() and call png_write_rows() the
-correct number of times to write all the sub-images
-(png_set_interlace_handling() returns the number of sub-images.)
-
-If you want libpng to build the sub-images, call this before you start
-writing any rows:
-
-    number_of_passes = png_set_interlace_handling(png_ptr);
-
-This will return the number of passes needed.  Currently, this is seven,
-but may change if another interlace type is added.
-
-Then write the complete image number_of_passes times.
-
-    png_write_rows(png_ptr, row_pointers, number_of_rows);
-
-Think carefully before you write an interlaced image.  Typically code that
-reads such images reads all the image data into memory, uncompressed, before
-doing any processing.  Only code that can display an image on the fly can
-take advantage of the interlacing and even then the image has to be exactly
-the correct size for the output device, because scaling an image requires
-adjacent pixels and these are not available until all the passes have been
-read.
-
-If you do write an interlaced image you will hardly ever need to handle
-the interlacing yourself.  Call png_set_interlace_handling() and use the
-approach described above.
-
-The only time it is conceivable that you will really need to write an
-interlaced image pass-by-pass is when you have read one pass by pass and
-made some pixel-by-pixel transformation to it, as described in the read
-code above.  In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros
-to determine the size of each sub-image in turn and simply write the rows
-you obtained from the read code.
-
-Finishing a sequential write
-
-After you are finished writing the image, you should finish writing
-the file.  If you are interested in writing comments or time, you should
-pass an appropriately filled png_info pointer.  If you are not interested,
-you can pass NULL.
-
-    png_write_end(png_ptr, info_ptr);
-
-When you are done, you can free all memory used by libpng like this:
-
-    png_destroy_write_struct(&png_ptr, &info_ptr);
-
-It is also possible to individually free the info_ptr members that
-point to libpng-allocated storage with the following function:
-
-    png_free_data(png_ptr, info_ptr, mask, seq)
-
-    mask  - identifies data to be freed, a mask
-            containing the bitwise OR of one or
-            more of
-              PNG_FREE_PLTE, PNG_FREE_TRNS,
-              PNG_FREE_HIST, PNG_FREE_ICCP,
-              PNG_FREE_PCAL, PNG_FREE_ROWS,
-              PNG_FREE_SCAL, PNG_FREE_SPLT,
-              PNG_FREE_TEXT, PNG_FREE_UNKN,
-            or simply PNG_FREE_ALL
-
-    seq   - sequence number of item to be freed
-            (-1 for all items)
-
-This function may be safely called when the relevant storage has
-already been freed, or has not yet been allocated, or was allocated
-by the user  and not by libpng,  and will in those cases do nothing.
-The "seq" parameter is ignored if only one item of the selected data
-type, such as PLTE, is allowed.  If "seq" is not -1, and multiple items
-are allowed for the data type identified in the mask, such as text or
-sPLT, only the n'th item in the structure is freed, where n is "seq".
-
-If you allocated data such as a palette that you passed in to libpng
-with png_set_*, you must not free it until just before the call to
-png_destroy_write_struct().
-
-The default behavior is only to free data that was allocated internally
-by libpng.  This can be changed, so that libpng will not free the data,
-or so that it will free data that was allocated by the user with png_malloc()
-or png_calloc() and passed in via a png_set_*() function, with
-
-    png_data_freer(png_ptr, info_ptr, freer, mask)
-
-    freer  - one of
-               PNG_DESTROY_WILL_FREE_DATA
-               PNG_SET_WILL_FREE_DATA
-               PNG_USER_WILL_FREE_DATA
-
-    mask   - which data elements are affected
-             same choices as in png_free_data()
-
-For example, to transfer responsibility for some data from a read structure
-to a write structure, you could use
-
-    png_data_freer(read_ptr, read_info_ptr,
-       PNG_USER_WILL_FREE_DATA,
-       PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
-
-    png_data_freer(write_ptr, write_info_ptr,
-       PNG_DESTROY_WILL_FREE_DATA,
-       PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
-
-thereby briefly reassigning responsibility for freeing to the user but
-immediately afterwards reassigning it once more to the write_destroy
-function.  Having done this, it would then be safe to destroy the read
-structure and continue to use the PLTE, tRNS, and hIST data in the write
-structure.
-
-This function only affects data that has already been allocated.
-You can call this function before calling after the png_set_*() functions
-to control whether the user or png_destroy_*() is supposed to free the data.
-When the user assumes responsibility for libpng-allocated data, the
-application must use
-png_free() to free it, and when the user transfers responsibility to libpng
-for data that the user has allocated, the user must have used png_malloc()
-or png_calloc() to allocate it.
-
-If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
-separately, do not transfer responsibility for freeing text_ptr to libpng,
-because when libpng fills a png_text structure it combines these members with
-the key member, and png_free_data() will free only text_ptr.key.  Similarly,
-if you transfer responsibility for free'ing text_ptr from libpng to your
-application, your application must not separately free those members.
-For a more compact example of writing a PNG image, see the file example.c.
-
-V. Simplified API
-
-The simplified API, which became available in libpng-1.6.0, hides the details
-of both libpng and the PNG file format itself.
-It allows PNG files to be read into a very limited number of
-in-memory bitmap formats or to be written from the same formats.  If these
-formats do not accommodate your needs then you can, and should, use the more
-sophisticated APIs above - these support a wide variety of in-memory formats
-and a wide variety of sophisticated transformations to those formats as well
-as a wide variety of APIs to manipulate ancilliary information.
-
-To read a PNG file using the simplified API:
-
-  1) Declare a 'png_image' structure (see below) on the stack, set the
-     version field to PNG_IMAGE_VERSION and the 'opaque' pointer to NULL
-     (this is REQUIRED, your program may crash if you don't do it.)
-
-  2) Call the appropriate png_image_begin_read... function.
-
-  3) Set the png_image 'format' member to the required sample format.
-
-  4) Allocate a buffer for the image and, if required, the color-map.
-
-  5) Call png_image_finish_read to read the image and, if required, the
-     color-map into your buffers.
-
-There are no restrictions on the format of the PNG input itself; all valid
-color types, bit depths, and interlace methods are acceptable, and the
-input image is transformed as necessary to the requested in-memory format
-during the png_image_finish_read() step.  The only caveat is that if you
-request a color-mapped image from a PNG that is full-color or makes
-complex use of an alpha channel the transformation is extremely lossy and the
-result may look terrible.
-
-To write a PNG file using the simplified API:
-
-  1) Declare a 'png_image' structure on the stack and memset()
-     it to all zero.
-
-  2) Initialize the members of the structure that describe the
-     image, setting the 'format' member to the format of the
-     image samples.
-
-  3) Call the appropriate png_image_write... function with a
-     pointer to the image and, if necessary, the color-map to write
-     the PNG data.
-
-png_image is a structure that describes the in-memory format of an image
-when it is being read or defines the in-memory format of an image that you
-need to write.  The "png_image" structure contains the following members:
-
-   png_controlp opaque  Initialize to NULL, free with png_image_free
-   png_uint_32  version Set to PNG_IMAGE_VERSION
-   png_uint_32  width   Image width in pixels (columns)
-   png_uint_32  height  Image height in pixels (rows)
-   png_uint_32  format  Image format as defined below
-   png_uint_32  flags   A bit mask containing informational flags
-   png_uint_32  colormap_entries; Number of entries in the color-map
-   png_uint_32  warning_or_error;
-   char         message[64];
-
-In the event of an error or warning the "warning_or_error"
-field will be set to a non-zero value and the 'message' field will contain
-a '\0' terminated string with the libpng error or warning message.  If both
-warnings and an error were encountered, only the error is recorded.  If there
-are multiple warnings, only the first one is recorded.
-
-The upper 30 bits of the "warning_or_error" value are reserved; the low two
-bits contain a two bit code such that a value more than 1 indicates a failure
-in the API just called:
-
-   0 - no warning or error
-   1 - warning
-   2 - error
-   3 - error preceded by warning
-
-The pixels (samples) of the image have one to four channels whose components
-have original values in the range 0 to 1.0:
-
-  1: A single gray or luminance channel (G).
-  2: A gray/luminance channel and an alpha channel (GA).
-  3: Three red, green, blue color channels (RGB).
-  4: Three color channels and an alpha channel (RGBA).
-
-The channels are encoded in one of two ways:
-
-  a) As a small integer, value 0..255, contained in a single byte.  For the
-alpha channel the original value is simply value/255.  For the color or
-luminance channels the value is encoded according to the sRGB specification
-and matches the 8-bit format expected by typical display devices.
-
-The color/gray channels are not scaled (pre-multiplied) by the alpha
-channel and are suitable for passing to color management software.
-
-  b) As a value in the range 0..65535, contained in a 2-byte integer, in
-the native byte order of the platform on which the application is running.
-All channels can be converted to the original value by dividing by 65535; all
-channels are linear.  Color channels use the RGB encoding (RGB end-points) of
-the sRGB specification.  This encoding is identified by the
-PNG_FORMAT_FLAG_LINEAR flag below.
-
-When the simplified API needs to convert between sRGB and linear colorspaces,
-the actual sRGB transfer curve defined in the sRGB specification (see the
-article at https://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
-approximation used elsewhere in libpng.
-
-When an alpha channel is present it is expected to denote pixel coverage
-of the color or luminance channels and is returned as an associated alpha
-channel: the color/gray channels are scaled (pre-multiplied) by the alpha
-value.
-
-The samples are either contained directly in the image data, between 1 and 8
-bytes per pixel according to the encoding, or are held in a color-map indexed
-by bytes in the image data.  In the case of a color-map the color-map entries
-are individual samples, encoded as above, and the image data has one byte per
-pixel to select the relevant sample from the color-map.
-
-PNG_FORMAT_*
-
-The #defines to be used in png_image::format.  Each #define identifies a
-particular layout of channel data and, if present, alpha values.  There are
-separate defines for each of the two component encodings.
-
-A format is built up using single bit flag values.  All combinations are
-valid.  Formats can be built up from the flag values or you can use one of
-the predefined values below.  When testing formats always use the FORMAT_FLAG
-macros to test for individual features - future versions of the library may
-add new flags.
-
-When reading or writing color-mapped images the format should be set to the
-format of the entries in the color-map then png_image_{read,write}_colormap
-called to read or write the color-map and set the format correctly for the
-image data.  Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly!
-
-NOTE: libpng can be built with particular features disabled. If you see
-compiler errors because the definition of one of the following flags has been
-compiled out it is because libpng does not have the required support.  It is
-possible, however, for the libpng configuration to enable the format on just
-read or just write; in that case you may see an error at run time.
-You can guard against this by checking for the definition of the
-appropriate "_SUPPORTED" macro, one of:
-
-   PNG_SIMPLIFIED_{READ,WRITE}_{BGR,AFIRST}_SUPPORTED
-
-   PNG_FORMAT_FLAG_ALPHA    format with an alpha channel
-   PNG_FORMAT_FLAG_COLOR    color format: otherwise grayscale
-   PNG_FORMAT_FLAG_LINEAR   2-byte channels else 1-byte
-   PNG_FORMAT_FLAG_COLORMAP image data is color-mapped
-   PNG_FORMAT_FLAG_BGR      BGR colors, else order is RGB
-   PNG_FORMAT_FLAG_AFIRST   alpha channel comes first
-
-Supported formats are as follows.  Future versions of libpng may support more
-formats; for compatibility with older versions simply check if the format
-macro is defined using #ifdef.  These defines describe the in-memory layout
-of the components of the pixels of the image.
-
-First the single byte (sRGB) formats:
-
-   PNG_FORMAT_GRAY
-   PNG_FORMAT_GA
-   PNG_FORMAT_AG
-   PNG_FORMAT_RGB
-   PNG_FORMAT_BGR
-   PNG_FORMAT_RGBA
-   PNG_FORMAT_ARGB
-   PNG_FORMAT_BGRA
-   PNG_FORMAT_ABGR
-
-Then the linear 2-byte formats.  When naming these "Y" is used to
-indicate a luminance (gray) channel.  The component order within the pixel
-is always the same - there is no provision for swapping the order of the
-components in the linear format.  The components are 16-bit integers in
-the native byte order for your platform, and there is no provision for
-swapping the bytes to a different endian condition.
-
-   PNG_FORMAT_LINEAR_Y
-   PNG_FORMAT_LINEAR_Y_ALPHA
-   PNG_FORMAT_LINEAR_RGB
-   PNG_FORMAT_LINEAR_RGB_ALPHA
-
-With color-mapped formats the image data is one byte for each pixel. The byte
-is an index into the color-map which is formatted as above.  To obtain a
-color-mapped format it is sufficient just to add the PNG_FOMAT_FLAG_COLORMAP
-to one of the above definitions, or you can use one of the definitions below.
-
-   PNG_FORMAT_RGB_COLORMAP
-   PNG_FORMAT_BGR_COLORMAP
-   PNG_FORMAT_RGBA_COLORMAP
-   PNG_FORMAT_ARGB_COLORMAP
-   PNG_FORMAT_BGRA_COLORMAP
-   PNG_FORMAT_ABGR_COLORMAP
-
-PNG_IMAGE macros
-
-These are convenience macros to derive information from a png_image
-structure.  The PNG_IMAGE_SAMPLE_ macros return values appropriate to the
-actual image sample values - either the entries in the color-map or the
-pixels in the image.  The PNG_IMAGE_PIXEL_ macros return corresponding values
-for the pixels and will always return 1 for color-mapped formats.  The
-remaining macros return information about the rows in the image and the
-complete image.
-
-NOTE: All the macros that take a png_image::format parameter are compile time
-constants if the format parameter is, itself, a constant.  Therefore these
-macros can be used in array declarations and case labels where required.
-Similarly the macros are also pre-processor constants (sizeof is not used) so
-they can be used in #if tests.
-
-  PNG_IMAGE_SAMPLE_CHANNELS(fmt)
-    Returns the total number of channels in a given format: 1..4
-
-  PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt)
-    Returns the size in bytes of a single component of a pixel or color-map
-    entry (as appropriate) in the image: 1 or 2.
-
-  PNG_IMAGE_SAMPLE_SIZE(fmt)
-    This is the size of the sample data for one sample.  If the image is
-    color-mapped it is the size of one color-map entry (and image pixels are
-    one byte in size), otherwise it is the size of one image pixel.
-
-  PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(fmt)
-    The maximum size of the color-map required by the format expressed in a
-    count of components.  This can be used to compile-time allocate a
-    color-map:
-
-    png_uint_16 colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(linear_fmt)];
-
-    png_byte colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(sRGB_fmt)];
-
-    Alternatively use the PNG_IMAGE_COLORMAP_SIZE macro below to use the
-    information from one of the png_image_begin_read_ APIs and dynamically
-    allocate the required memory.
-
-  PNG_IMAGE_COLORMAP_SIZE(fmt)
-   The size of the color-map required by the format; this is the size of the
-   color-map buffer passed to the png_image_{read,write}_colormap APIs. It is
-   a fixed number determined by the format so can easily be allocated on the
-   stack if necessary.
-
-Corresponding information about the pixels
-
-  PNG_IMAGE_PIXEL_CHANNELS(fmt)
-   The number of separate channels (components) in a pixel; 1 for a
-   color-mapped image.
-
-  PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)\
-   The size, in bytes, of each component in a pixel; 1 for a color-mapped
-   image.
-
-  PNG_IMAGE_PIXEL_SIZE(fmt)
-   The size, in bytes, of a complete pixel; 1 for a color-mapped image.
-
-Information about the whole row, or whole image
-
-  PNG_IMAGE_ROW_STRIDE(image)
-   Returns the total number of components in a single row of the image; this
-   is the minimum 'row stride', the minimum count of components between each
-   row.  For a color-mapped image this is the minimum number of bytes in a
-   row.
-
-   If you need the stride measured in bytes, row_stride_bytes is
-   PNG_IMAGE_ROW_STRIDE(image) * PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)
-   plus any padding bytes that your application might need, for example
-   to start the next row on a 4-byte boundary.
-
-  PNG_IMAGE_BUFFER_SIZE(image, row_stride)
-   Return the size, in bytes, of an image buffer given a png_image and a row
-   stride - the number of components to leave space for in each row.
-
-  PNG_IMAGE_SIZE(image)
-   Return the size, in bytes, of the image in memory given just a png_image;
-   the row stride is the minimum stride required for the image.
-
-  PNG_IMAGE_COLORMAP_SIZE(image)
-   Return the size, in bytes, of the color-map of this image.  If the image
-   format is not a color-map format this will return a size sufficient for
-   256 entries in the given format; check PNG_FORMAT_FLAG_COLORMAP if
-   you don't want to allocate a color-map in this case.
-
-PNG_IMAGE_FLAG_*
-
-Flags containing additional information about the image are held in
-the 'flags' field of png_image.
-
-  PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB == 0x01
-    This indicates the the RGB values of the in-memory bitmap do not
-    correspond to the red, green and blue end-points defined by sRGB.
-
-  PNG_IMAGE_FLAG_FAST == 0x02
-   On write emphasise speed over compression; the resultant PNG file will be
-   larger but will be produced significantly faster, particular for large
-   images.  Do not use this option for images which will be distributed, only
-   used it when producing intermediate files that will be read back in
-   repeatedly.  For a typical 24-bit image the option will double the read
-   speed at the cost of increasing the image size by 25%, however for many
-   more compressible images the PNG file can be 10 times larger with only a
-   slight speed gain.
-
-  PNG_IMAGE_FLAG_16BIT_sRGB == 0x04
-    On read if the image is a 16-bit per component image and there is no gAMA
-    or sRGB chunk assume that the components are sRGB encoded.  Notice that
-    images output by the simplified API always have gamma information; setting
-    this flag only affects the interpretation of 16-bit images from an
-    external source.  It is recommended that the application expose this flag
-    to the user; the user can normally easily recognize the difference between
-    linear and sRGB encoding.  This flag has no effect on write - the data
-    passed to the write APIs must have the correct encoding (as defined
-    above.)
-
-    If the flag is not set (the default) input 16-bit per component data is
-    assumed to be linear.
-
-    NOTE: the flag can only be set after the png_image_begin_read_ call,
-    because that call initializes the 'flags' field.
-
-READ APIs
-
-   The png_image passed to the read APIs must have been initialized by setting
-   the png_controlp field 'opaque' to NULL (or, better, memset the whole thing.)
-
-   int png_image_begin_read_from_file( png_imagep image,
-     const char *file_name)
-
-     The named file is opened for read and the image header
-     is filled in from the PNG header in the file.
-
-   int png_image_begin_read_from_stdio (png_imagep image,
-     FILE* file)
-
-      The PNG header is read from the stdio FILE object.
-
-   int png_image_begin_read_from_memory(png_imagep image,
-      png_const_voidp memory, png_size_t size)
-
-      The PNG header is read from the given memory buffer.
-
-   int png_image_finish_read(png_imagep image,
-      png_colorp background, void *buffer,
-      png_int_32 row_stride, void *colormap));
-
-      Finish reading the image into the supplied buffer and
-      clean up the png_image structure.
-
-      row_stride is the step, in png_byte or png_uint_16 units
-      as appropriate, between adjacent rows.  A positive stride
-      indicates that the top-most row is first in the buffer -
-      the normal top-down arrangement.  A negative stride
-      indicates that the bottom-most row is first in the buffer.
-
-      background need only be supplied if an alpha channel must
-      be removed from a png_byte format and the removal is to be
-      done by compositing on a solid color; otherwise it may be
-      NULL and any composition will be done directly onto the
-      buffer.  The value is an sRGB color to use for the
-      background, for grayscale output the green channel is used.
-
-      For linear output removing the alpha channel is always done
-      by compositing on black.
-
-   void png_image_free(png_imagep image)
-
-      Free any data allocated by libpng in image->opaque,
-      setting the pointer to NULL.  May be called at any time
-      after the structure is initialized.
-
-When the simplified API needs to convert between sRGB and linear colorspaces,
-the actual sRGB transfer curve defined in the sRGB specification (see the
-article at https://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
-approximation used elsewhere in libpng.
-
-WRITE APIS
-
-For write you must initialize a png_image structure to describe the image to
-be written:
-
-   version: must be set to PNG_IMAGE_VERSION
-   opaque: must be initialized to NULL
-   width: image width in pixels
-   height: image height in rows
-   format: the format of the data you wish to write
-   flags: set to 0 unless one of the defined flags applies; set
-      PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB for color format images
-      where the RGB values do not correspond to the colors in sRGB.
-   colormap_entries: set to the number of entries in the color-map (0 to 256)
-
-   int png_image_write_to_file, (png_imagep image,
-      const char *file, int convert_to_8bit, const void *buffer,
-      png_int_32 row_stride, const void *colormap));
-
-      Write the image to the named file.
-
-   int png_image_write_to_memory (png_imagep image, void *memory,
-      png_alloc_size_t * PNG_RESTRICT memory_bytes,
-      int convert_to_8_bit, const void *buffer, ptrdiff_t row_stride,
-      const void *colormap));
-
-      Write the image to memory.
-
-   int png_image_write_to_stdio(png_imagep image, FILE *file,
-      int convert_to_8_bit, const void *buffer,
-      png_int_32 row_stride, const void *colormap)
-
-      Write the image to the given (FILE*).
-
-With all write APIs if image is in one of the linear formats with
-(png_uint_16) data then setting convert_to_8_bit will cause the output to be
-a (png_byte) PNG gamma encoded according to the sRGB specification, otherwise
-a 16-bit linear encoded PNG file is written.
-
-With all APIs row_stride is handled as in the read APIs - it is the spacing
-from one row to the next in component sized units (float) and if negative
-indicates a bottom-up row layout in the buffer.  If you pass zero, libpng will
-calculate the row_stride for you from the width and number of channels.
-
-Note that the write API does not support interlacing, sub-8-bit pixels,
-indexed (paletted) images, or most ancillary chunks.
-
-VI. Modifying/Customizing libpng
-
-There are two issues here.  The first is changing how libpng does
-standard things like memory allocation, input/output, and error handling.
-The second deals with more complicated things like adding new chunks,
-adding new transformations, and generally changing how libpng works.
-Both of those are compile-time issues; that is, they are generally
-determined at the time the code is written, and there is rarely a need
-to provide the user with a means of changing them.
-
-Memory allocation, input/output, and error handling
-
-All of the memory allocation, input/output, and error handling in libpng
-goes through callbacks that are user-settable.  The default routines are
-in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively.  To change
-these functions, call the appropriate png_set_*_fn() function.
-
-Memory allocation is done through the functions png_malloc(), png_calloc(),
-and png_free().  The png_malloc() and png_free() functions currently just
-call the standard C functions and png_calloc() calls png_malloc() and then
-clears the newly allocated memory to zero; note that png_calloc(png_ptr, size)
-is not the same as the calloc(number, size) function provided by stdlib.h.
-There is limited support for certain systems with segmented memory
-architectures and the types of pointers declared by png.h match this; you
-will have to use appropriate pointers in your application.  If you prefer
-to use a different method of allocating and freeing data, you can use
-png_create_read_struct_2() or png_create_write_struct_2() to register your
-own functions as described above.  These functions also provide a void
-pointer that can be retrieved via
-
-    mem_ptr=png_get_mem_ptr(png_ptr);
-
-Your replacement memory functions must have prototypes as follows:
-
-    png_voidp malloc_fn(png_structp png_ptr,
-       png_alloc_size_t size);
-
-    void free_fn(png_structp png_ptr, png_voidp ptr);
-
-Your malloc_fn() must return NULL in case of failure.  The png_malloc()
-function will normally call png_error() if it receives a NULL from the
-system memory allocator or from your replacement malloc_fn().
-
-Your free_fn() will never be called with a NULL ptr, since libpng's
-png_free() checks for NULL before calling free_fn().
-
-Input/Output in libpng is done through png_read() and png_write(),
-which currently just call fread() and fwrite().  The FILE * is stored in
-png_struct and is initialized via png_init_io().  If you wish to change
-the method of I/O, the library supplies callbacks that you can set
-through the function png_set_read_fn() and png_set_write_fn() at run
-time, instead of calling the png_init_io() function.  These functions
-also provide a void pointer that can be retrieved via the function
-png_get_io_ptr().  For example:
-
-    png_set_read_fn(png_structp read_ptr,
-        voidp read_io_ptr, png_rw_ptr read_data_fn)
-
-    png_set_write_fn(png_structp write_ptr,
-        voidp write_io_ptr, png_rw_ptr write_data_fn,
-        png_flush_ptr output_flush_fn);
-
-    voidp read_io_ptr = png_get_io_ptr(read_ptr);
-    voidp write_io_ptr = png_get_io_ptr(write_ptr);
-
-The replacement I/O functions must have prototypes as follows:
-
-    void user_read_data(png_structp png_ptr,
-        png_bytep data, png_size_t length);
-
-    void user_write_data(png_structp png_ptr,
-        png_bytep data, png_size_t length);
-
-    void user_flush_data(png_structp png_ptr);
-
-The user_read_data() function is responsible for detecting and
-handling end-of-data errors.
-
-Supplying NULL for the read, write, or flush functions sets them back
-to using the default C stream functions, which expect the io_ptr to
-point to a standard *FILE structure.  It is probably a mistake
-to use NULL for one of write_data_fn and output_flush_fn but not both
-of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined.
-It is an error to read from a write stream, and vice versa.
-
-Error handling in libpng is done through png_error() and png_warning().
-Errors handled through png_error() are fatal, meaning that png_error()
-should never return to its caller.  Currently, this is handled via
-setjmp() and longjmp() (unless you have compiled libpng with
-PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
-but you could change this to do things like exit() if you should wish,
-as long as your function does not return.
-
-On non-fatal errors, png_warning() is called
-to print a warning message, and then control returns to the calling code.
-By default png_error() and png_warning() print a message on stderr via
-fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
-(because you don't want the messages) or PNG_NO_STDIO defined (because
-fprintf() isn't available).  If you wish to change the behavior of the error
-functions, you will need to set up your own message callbacks.  These
-functions are normally supplied at the time that the png_struct is created.
-It is also possible to redirect errors and warnings to your own replacement
-functions after png_create_*_struct() has been called by calling:
-
-    png_set_error_fn(png_structp png_ptr,
-        png_voidp error_ptr, png_error_ptr error_fn,
-        png_error_ptr warning_fn);
-
-If NULL is supplied for either error_fn or warning_fn, then the libpng
-default function will be used, calling fprintf() and/or longjmp() if a
-problem is encountered.  The replacement error functions should have
-parameters as follows:
-
-    void user_error_fn(png_structp png_ptr,
-        png_const_charp error_msg);
-
-    void user_warning_fn(png_structp png_ptr,
-        png_const_charp warning_msg);
-
-Then, within your user_error_fn or user_warning_fn, you can retrieve
-the error_ptr if you need it, by calling
-
-    png_voidp error_ptr = png_get_error_ptr(png_ptr);
-
-The motivation behind using setjmp() and longjmp() is the C++ throw and
-catch exception handling methods.  This makes the code much easier to write,
-as there is no need to check every return code of every function call.
-However, there are some uncertainties about the status of local variables
-after a longjmp, so the user may want to be careful about doing anything
-after setjmp returns non-zero besides returning itself.  Consult your
-compiler documentation for more details.  For an alternative approach, you
-may wish to use the "cexcept" facility (see https://cexcept.sourceforge.io/),
-which is illustrated in pngvalid.c and in contrib/visupng.
-
-Beginning in libpng-1.4.0, the png_set_benign_errors() API became available.
-You can use this to handle certain errors (normally handled as errors)
-as warnings.
-
-    png_set_benign_errors (png_ptr, int allowed);
-
-    allowed: 0: treat png_benign_error() as an error.
-             1: treat png_benign_error() as a warning.
-
-As of libpng-1.6.0, the default condition is to treat benign errors as
-warnings while reading and as errors while writing.
-
-Custom chunks
-
-If you need to read or write custom chunks, you may need to get deeper
-into the libpng code.  The library now has mechanisms for storing
-and writing chunks of unknown type; you can even declare callbacks
-for custom chunks.  However, this may not be good enough if the
-library code itself needs to know about interactions between your
-chunk and existing `intrinsic' chunks.
-
-If you need to write a new intrinsic chunk, first read the PNG
-specification. Acquire a first level of understanding of how it works.
-Pay particular attention to the sections that describe chunk names,
-and look at how other chunks were designed, so you can do things
-similarly.  Second, check out the sections of libpng that read and
-write chunks.  Try to find a chunk that is similar to yours and use
-it as a template.  More details can be found in the comments inside
-the code.  It is best to handle private or unknown chunks in a generic method,
-via callback functions, instead of by modifying libpng functions. This
-is illustrated in pngtest.c, which uses a callback function to handle a
-private "vpAg" chunk and the new "sTER" chunk, which are both unknown to
-libpng.
-
-If you wish to write your own transformation for the data, look through
-the part of the code that does the transformations, and check out some of
-the simpler ones to get an idea of how they work.  Try to find a similar
-transformation to the one you want to add and copy off of it.  More details
-can be found in the comments inside the code itself.
-
-Configuring for gui/windowing platforms:
-
-You will need to write new error and warning functions that use the GUI
-interface, as described previously, and set them to be the error and
-warning functions at the time that png_create_*_struct() is called,
-in order to have them available during the structure initialization.
-They can be changed later via png_set_error_fn().  On some compilers,
-you may also have to change the memory allocators (png_malloc, etc.).
-
-Configuring zlib:
-
-There are special functions to configure the compression.  Perhaps the
-most useful one changes the compression level, which currently uses
-input compression values in the range 0 - 9.  The library normally
-uses the default compression level (Z_DEFAULT_COMPRESSION = 6).  Tests
-have shown that for a large majority of images, compression values in
-the range 3-6 compress nearly as well as higher levels, and do so much
-faster.  For online applications it may be desirable to have maximum speed
-(Z_BEST_SPEED = 1).  With versions of zlib after v0.99, you can also
-specify no compression (Z_NO_COMPRESSION = 0), but this would create
-files larger than just storing the raw bitmap.  You can specify the
-compression level by calling:
-
-    #include zlib.h
-    png_set_compression_level(png_ptr, level);
-
-Another useful one is to reduce the memory level used by the library.
-The memory level defaults to 8, but it can be lowered if you are
-short on memory (running DOS, for example, where you only have 640K).
-Note that the memory level does have an effect on compression; among
-other things, lower levels will result in sections of incompressible
-data being emitted in smaller stored blocks, with a correspondingly
-larger relative overhead of up to 15% in the worst case.
-
-    #include zlib.h
-    png_set_compression_mem_level(png_ptr, level);
-
-The other functions are for configuring zlib.  They are not recommended
-for normal use and may result in writing an invalid PNG file.  See
-zlib.h for more information on what these mean.
-
-    #include zlib.h
-    png_set_compression_strategy(png_ptr,
-        strategy);
-
-    png_set_compression_window_bits(png_ptr,
-        window_bits);
-
-    png_set_compression_method(png_ptr, method);
-
-This controls the size of the IDAT chunks (default 8192):
-
-    png_set_compression_buffer_size(png_ptr, size);
-
-As of libpng version 1.5.4, additional APIs became
-available to set these separately for non-IDAT
-compressed chunks such as zTXt, iTXt, and iCCP:
-
-    #include zlib.h
-    #if PNG_LIBPNG_VER >= 10504
-    png_set_text_compression_level(png_ptr, level);
-
-    png_set_text_compression_mem_level(png_ptr, level);
-
-    png_set_text_compression_strategy(png_ptr,
-        strategy);
-
-    png_set_text_compression_window_bits(png_ptr,
-        window_bits);
-
-    png_set_text_compression_method(png_ptr, method);
-    #endif
-
-Controlling row filtering
-
-If you want to control whether libpng uses filtering or not, which
-filters are used, and how it goes about picking row filters, you
-can call one of these functions.  The selection and configuration
-of row filters can have a significant impact on the size and
-encoding speed and a somewhat lesser impact on the decoding speed
-of an image.  Filtering is enabled by default for RGB and grayscale
-images (with and without alpha), but not for paletted images nor
-for any images with bit depths less than 8 bits/pixel.
-
-The 'method' parameter sets the main filtering method, which is
-currently only '0' in the PNG 1.2 specification.  The 'filters'
-parameter sets which filter(s), if any, should be used for each
-scanline.  Possible values are PNG_ALL_FILTERS, PNG_NO_FILTERS,
-or PNG_FAST_FILTERS to turn filtering on and off, or to turn on
-just the fast-decoding subset of filters, respectively.
-
-Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
-PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
-ORed together with '|' to specify one or more filters to use.
-These filters are described in more detail in the PNG specification.
-If you intend to change the filter type during the course of writing
-the image, you should start with flags set for all of the filters
-you intend to use so that libpng can initialize its internal
-structures appropriately for all of the filter types.  (Note that this
-means the first row must always be adaptively filtered, because libpng
-currently does not allocate the filter buffers until png_write_row()
-is called for the first time.)
-
-    filters = PNG_NO_FILTERS;
-    filters = PNG_ALL_FILTERS;
-    filters = PNG_FAST_FILTERS;
-
-    or
-
-    filters = PNG_FILTER_NONE | PNG_FILTER_SUB |
-              PNG_FILTER_UP | PNG_FILTER_AVG |
-              PNG_FILTER_PAETH;
-
-    png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
-       filters);
-
-              The second parameter can also be
-              PNG_INTRAPIXEL_DIFFERENCING if you are
-              writing a PNG to be embedded in a MNG
-              datastream.  This parameter must be the
-              same as the value of filter_method used
-              in png_set_IHDR().
-
-Requesting debug printout
-
-The macro definition PNG_DEBUG can be used to request debugging
-printout.  Set it to an integer value in the range 0 to 3.  Higher
-numbers result in increasing amounts of debugging information.  The
-information is printed to the "stderr" file, unless another file
-name is specified in the PNG_DEBUG_FILE macro definition.
-
-When PNG_DEBUG > 0, the following functions (macros) become available:
-
-   png_debug(level, message)
-   png_debug1(level, message, p1)
-   png_debug2(level, message, p1, p2)
-
-in which "level" is compared to PNG_DEBUG to decide whether to print
-the message, "message" is the formatted string to be printed,
-and p1 and p2 are parameters that are to be embedded in the string
-according to printf-style formatting directives.  For example,
-
-   png_debug1(2, "foo=%d", foo);
-
-is expanded to
-
-   if (PNG_DEBUG > 2)
-      fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
-
-When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
-can still use PNG_DEBUG to control your own debugging:
-
-   #ifdef PNG_DEBUG
-       fprintf(stderr, ...
-   #endif
-
-When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
-having level = 0 will be printed.  There aren't any such statements in
-this version of libpng, but if you insert some they will be printed.
-
-VII.  MNG support
-
-The MNG specification (available at http://www.libpng.org/pub/mng) allows
-certain extensions to PNG for PNG images that are embedded in MNG datastreams.
-Libpng can support some of these extensions.  To enable them, use the
-png_permit_mng_features() function:
-
-   feature_set = png_permit_mng_features(png_ptr, mask)
-
-   mask is a png_uint_32 containing the bitwise OR of the
-        features you want to enable.  These include
-        PNG_FLAG_MNG_EMPTY_PLTE
-        PNG_FLAG_MNG_FILTER_64
-        PNG_ALL_MNG_FEATURES
-
-   feature_set is a png_uint_32 that is the bitwise AND of
-      your mask with the set of MNG features that is
-      supported by the version of libpng that you are using.
-
-It is an error to use this function when reading or writing a standalone
-PNG file with the PNG 8-byte signature.  The PNG datastream must be wrapped
-in a MNG datastream.  As a minimum, it must have the MNG 8-byte signature
-and the MHDR and MEND chunks.  Libpng does not provide support for these
-or any other MNG chunks; your application must provide its own support for
-them.  You may wish to consider using libmng (available at
-https://www.libmng.com/) instead.
-
-VIII.  Changes to Libpng from version 0.88
-
-It should be noted that versions of libpng later than 0.96 are not
-distributed by the original libpng author, Guy Schalnat, nor by
-Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
-distributed versions 0.89 through 0.96, but rather by another member
-of the original PNG Group, Glenn Randers-Pehrson.  Guy and Andreas are
-still alive and well, but they have moved on to other things.
-
-The old libpng functions png_read_init(), png_write_init(),
-png_info_init(), png_read_destroy(), and png_write_destroy() have been
-moved to PNG_INTERNAL in version 0.95 to discourage their use.  These
-functions will be removed from libpng version 1.4.0.
-
-The preferred method of creating and initializing the libpng structures is
-via the png_create_read_struct(), png_create_write_struct(), and
-png_create_info_struct() because they isolate the size of the structures
-from the application, allow version error checking, and also allow the
-use of custom error handling routines during the initialization, which
-the old functions do not.  The functions png_read_destroy() and
-png_write_destroy() do not actually free the memory that libpng
-allocated for these structs, but just reset the data structures, so they
-can be used instead of png_destroy_read_struct() and
-png_destroy_write_struct() if you feel there is too much system overhead
-allocating and freeing the png_struct for each image read.
-
-Setting the error callbacks via png_set_message_fn() before
-png_read_init() as was suggested in libpng-0.88 is no longer supported
-because this caused applications that do not use custom error functions
-to fail if the png_ptr was not initialized to zero.  It is still possible
-to set the error callbacks AFTER png_read_init(), or to change them with
-png_set_error_fn(), which is essentially the same function, but with a new
-name to force compilation errors with applications that try to use the old
-method.
-
-Support for the sCAL, iCCP, iTXt, and sPLT chunks was added at libpng-1.0.6;
-however, iTXt support was not enabled by default.
-
-Starting with version 1.0.7, you can find out which version of the library
-you are using at run-time:
-
-   png_uint_32 libpng_vn = png_access_version_number();
-
-The number libpng_vn is constructed from the major version, minor
-version with leading zero, and release number with leading zero,
-(e.g., libpng_vn for version 1.0.7 is 10007).
-
-Note that this function does not take a png_ptr, so you can call it
-before you've created one.
-
-You can also check which version of png.h you used when compiling your
-application:
-
-   png_uint_32 application_vn = PNG_LIBPNG_VER;
-
-IX.  Changes to Libpng from version 1.0.x to 1.2.x
-
-Support for user memory management was enabled by default.  To
-accomplish this, the functions png_create_read_struct_2(),
-png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
-png_malloc_default(), and png_free_default() were added.
-
-Support for the iTXt chunk has been enabled by default as of
-version 1.2.41.
-
-Support for certain MNG features was enabled.
-
-Support for numbered error messages was added.  However, we never got
-around to actually numbering the error messages.  The function
-png_set_strip_error_numbers() was added (Note: the prototype for this
-function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE
-builds of libpng-1.2.15.  It was restored in libpng-1.2.36).
-
-The png_malloc_warn() function was added at libpng-1.2.3.  This issues
-a png_warning and returns NULL instead of aborting when it fails to
-acquire the requested memory allocation.
-
-Support for setting user limits on image width and height was enabled
-by default.  The functions png_set_user_limits(), png_get_user_width_max(),
-and png_get_user_height_max() were added at libpng-1.2.6.
-
-The png_set_add_alpha() function was added at libpng-1.2.7.
-
-The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9.
-Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the
-tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is
-deprecated.
-
-A number of macro definitions in support of runtime selection of
-assembler code features (especially Intel MMX code support) were
-added at libpng-1.2.0:
-
-    PNG_ASM_FLAG_MMX_SUPPORT_COMPILED
-    PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU
-    PNG_ASM_FLAG_MMX_READ_COMBINE_ROW
-    PNG_ASM_FLAG_MMX_READ_INTERLACE
-    PNG_ASM_FLAG_MMX_READ_FILTER_SUB
-    PNG_ASM_FLAG_MMX_READ_FILTER_UP
-    PNG_ASM_FLAG_MMX_READ_FILTER_AVG
-    PNG_ASM_FLAG_MMX_READ_FILTER_PAETH
-    PNG_ASM_FLAGS_INITIALIZED
-    PNG_MMX_READ_FLAGS
-    PNG_MMX_FLAGS
-    PNG_MMX_WRITE_FLAGS
-    PNG_MMX_FLAGS
-
-We added the following functions in support of runtime
-selection of assembler code features:
-
-    png_get_mmx_flagmask()
-    png_set_mmx_thresholds()
-    png_get_asm_flags()
-    png_get_mmx_bitdepth_threshold()
-    png_get_mmx_rowbytes_threshold()
-    png_set_asm_flags()
-
-We replaced all of these functions with simple stubs in libpng-1.2.20,
-when the Intel assembler code was removed due to a licensing issue.
-
-These macros are deprecated:
-
-    PNG_READ_TRANSFORMS_NOT_SUPPORTED
-    PNG_PROGRESSIVE_READ_NOT_SUPPORTED
-    PNG_NO_SEQUENTIAL_READ_SUPPORTED
-    PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
-    PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
-    PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
-
-They have been replaced, respectively, by:
-
-    PNG_NO_READ_TRANSFORMS
-    PNG_NO_PROGRESSIVE_READ
-    PNG_NO_SEQUENTIAL_READ
-    PNG_NO_WRITE_TRANSFORMS
-    PNG_NO_READ_ANCILLARY_CHUNKS
-    PNG_NO_WRITE_ANCILLARY_CHUNKS
-
-PNG_MAX_UINT was replaced with PNG_UINT_31_MAX.  It has been
-deprecated since libpng-1.0.16 and libpng-1.2.6.
-
-The function
-    png_check_sig(sig, num)
-was replaced with
-    !png_sig_cmp(sig, 0, num)
-It has been deprecated since libpng-0.90.
-
-The function
-    png_set_gray_1_2_4_to_8()
-which also expands tRNS to alpha was replaced with
-    png_set_expand_gray_1_2_4_to_8()
-which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
-
-X.  Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
-
-Private libpng prototypes and macro definitions were moved from
-png.h and pngconf.h into a new pngpriv.h header file.
-
-Functions png_set_benign_errors(), png_benign_error(), and
-png_chunk_benign_error() were added.
-
-Support for setting the maximum amount of memory that the application
-will allocate for reading chunks was added, as a security measure.
-The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
-were added to the library.
-
-We implemented support for I/O states by adding png_ptr member io_state
-and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
-
-We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
-input transforms.
-
-Checking for and reporting of errors in the IHDR chunk is more thorough.
-
-Support for global arrays was removed, to improve thread safety.
-
-Some obsolete/deprecated macros and functions have been removed.
-
-Typecasted NULL definitions such as
-   #define png_voidp_NULL            (png_voidp)NULL
-were eliminated.  If you used these in your application, just use
-NULL instead.
-
-The png_struct and info_struct members "trans" and "trans_values" were
-changed to "trans_alpha" and "trans_color", respectively.
-
-The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles
-were removed.
-
-The PNG_1_0_X and PNG_1_2_X macros were eliminated.
-
-The PNG_LEGACY_SUPPORTED macro was eliminated.
-
-Many WIN32_WCE #ifdefs were removed.
-
-The functions png_read_init(info_ptr), png_write_init(info_ptr),
-png_info_init(info_ptr), png_read_destroy(), and png_write_destroy()
-have been removed.  They have been deprecated since libpng-0.95.
-
-The png_permit_empty_plte() was removed. It has been deprecated
-since libpng-1.0.9.  Use png_permit_mng_features() instead.
-
-We removed the obsolete stub functions png_get_mmx_flagmask(),
-png_set_mmx_thresholds(), png_get_asm_flags(),
-png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(),
-png_set_asm_flags(), and png_mmx_supported()
-
-We removed the obsolete png_check_sig(), png_memcpy_check(), and
-png_memset_check() functions.  Instead use !png_sig_cmp(), memcpy(),
-and memset(), respectively.
-
-The function png_set_gray_1_2_4_to_8() was removed. It has been
-deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with
-png_set_expand_gray_1_2_4_to_8() because the former function also
-expanded any tRNS chunk to an alpha channel.
-
-Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32
-were added and are used by default instead of the corresponding
-functions. Unfortunately,
-from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
-function) incorrectly returned a value of type png_uint_32.
-
-We changed the prototype for png_malloc() from
-    png_malloc(png_structp png_ptr, png_uint_32 size)
-to
-    png_malloc(png_structp png_ptr, png_alloc_size_t size)
-
-This also applies to the prototype for the user replacement malloc_fn().
-
-The png_calloc() function was added and is used in place of
-of "png_malloc(); memset();" except in the case in png_read_png()
-where the array consists of pointers; in this case a "for" loop is used
-after the png_malloc() to set the pointers to NULL, to give robust.
-behavior in case the application runs out of memory part-way through
-the process.
-
-We changed the prototypes of png_get_compression_buffer_size() and
-png_set_compression_buffer_size() to work with png_size_t instead of
-png_uint_32.
-
-Support for numbered error messages was removed by default, since we
-never got around to actually numbering the error messages. The function
-png_set_strip_error_numbers() was removed from the library by default.
-
-The png_zalloc() and png_zfree() functions are no longer exported.
-The png_zalloc() function no longer zeroes out the memory that it
-allocates.  Applications that called png_zalloc(png_ptr, number, size)
-can call png_calloc(png_ptr, number*size) instead, and can call
-png_free() instead of png_zfree().
-
-Support for dithering was disabled by default in libpng-1.4.0, because
-it has not been well tested and doesn't actually "dither".
-The code was not
-removed, however, and could be enabled by building libpng with
-PNG_READ_DITHER_SUPPORTED defined.  In libpng-1.4.2, this support
-was re-enabled, but the function was renamed png_set_quantize() to
-reflect more accurately what it actually does.  At the same time,
-the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
-PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED
-was renamed to PNG_READ_QUANTIZE_SUPPORTED.
-
-We removed the trailing '.' from the warning and error messages.
-
-XI.  Changes to Libpng from version 1.4.x to 1.5.x
-
-From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
-function) incorrectly returned a value of type png_uint_32.
-The incorrect macro was removed from libpng-1.4.5.
-
-Checking for invalid palette index on write was added at libpng
-1.5.10.  If a pixel contains an invalid (out-of-range) index libpng issues
-a benign error.  This is enabled by default because this condition is an
-error according to the PNG specification, Clause 11.3.2, but the error can
-be ignored in each png_ptr with
-
-   png_set_check_for_invalid_index(png_ptr, allowed);
-
-      allowed  - one of
-                 0: disable benign error (accept the
-                    invalid data without warning).
-                 1: enable benign error (treat the
-                    invalid data as an error or a
-                    warning).
-
-If the error is ignored, or if png_benign_error() treats it as a warning,
-any invalid pixels are decoded as opaque black by the decoder and written
-as-is by the encoder.
-
-Retrieving the maximum palette index found was added at libpng-1.5.15.
-This statement must appear after png_read_png() or png_read_image() while
-reading, and after png_write_png() or png_write_image() while writing.
-
-   int max_palette = png_get_palette_max(png_ptr, info_ptr);
-
-This will return the maximum palette index found in the image, or "-1" if
-the palette was not checked, or "0" if no palette was found.  Note that this
-does not account for any palette index used by ancillary chunks such as the
-bKGD chunk; you must check those separately to determine the maximum
-palette index actually used.
-
-There are no substantial API changes between the non-deprecated parts of
-the 1.4.5 API and the 1.5.0 API; however, the ability to directly access
-members of the main libpng control structures, png_struct and png_info,
-deprecated in earlier versions of libpng, has been completely removed from
-libpng 1.5, and new private "pngstruct.h", "pnginfo.h", and "pngdebug.h"
-header files were created.
-
-We no longer include zlib.h in png.h.  The include statement has been moved
-to pngstruct.h, where it is not accessible by applications. Applications that
-need access to information in zlib.h will need to add the '#include "zlib.h"'
-directive.  It does not matter whether this is placed prior to or after
-the '"#include png.h"' directive.
-
-The png_sprintf(), png_strcpy(), and png_strncpy() macros are no longer used
-and were removed.
-
-We moved the png_strlen(), png_memcpy(), png_memset(), and png_memcmp()
-macros into a private header file (pngpriv.h) that is not accessible to
-applications.
-
-In png_get_iCCP, the type of "profile" was changed from png_charpp
-to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep.
-
-There are changes of form in png.h, including new and changed macros to
-declare parts of the API.  Some API functions with arguments that are
-pointers to data not modified within the function have been corrected to
-declare these arguments with PNG_CONST.
-
-Much of the internal use of C macros to control the library build has also
-changed and some of this is visible in the exported header files, in
-particular the use of macros to control data and API elements visible
-during application compilation may require significant revision to
-application code.  (It is extremely rare for an application to do this.)
-
-Any program that compiled against libpng 1.4 and did not use deprecated
-features or access internal library structures should compile and work
-against libpng 1.5, except for the change in the prototype for
-png_get_iCCP() and png_set_iCCP() API functions mentioned above.
-
-libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of
-interlaced images.  The macros return the number of rows and columns in
-each pass and information that can be used to de-interlace and (if
-absolutely necessary) interlace an image.
-
-libpng 1.5.0 adds an API png_longjmp(png_ptr, value).  This API calls
-the application-provided png_longjmp_ptr on the internal, but application
-initialized, longjmp buffer.  It is provided as a convenience to avoid
-the need to use the png_jmpbuf macro, which had the unnecessary side
-effect of resetting the internal png_longjmp_ptr value.
-
-libpng 1.5.0 includes a complete fixed point API.  By default this is
-present along with the corresponding floating point API.  In general the
-fixed point API is faster and smaller than the floating point one because
-the PNG file format used fixed point, not floating point.  This applies
-even if the library uses floating point in internal calculations.  A new
-macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library
-uses floating point arithmetic (the default) or fixed point arithmetic
-internally for performance critical calculations such as gamma correction.
-In some cases, the gamma calculations may produce slightly different
-results.  This has changed the results in png_rgb_to_gray and in alpha
-composition (png_set_background for example). This applies even if the
-original image was already linear (gamma == 1.0) and, therefore, it is
-not necessary to linearize the image.  This is because libpng has *not*
-been changed to optimize that case correctly, yet.
-
-Fixed point support for the sCAL chunk comes with an important caveat;
-the sCAL specification uses a decimal encoding of floating point values
-and the accuracy of PNG fixed point values is insufficient for
-representation of these values. Consequently a "string" API
-(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading
-arbitrary sCAL chunks in the absence of either the floating point API or
-internal floating point calculations.  Starting with libpng-1.5.0, both
-of these functions are present when PNG_sCAL_SUPPORTED is defined.  Prior
-to libpng-1.5.0, their presence also depended upon PNG_FIXED_POINT_SUPPORTED
-being defined and PNG_FLOATING_POINT_SUPPORTED not being defined.
-
-Applications no longer need to include the optional distribution header
-file pngusr.h or define the corresponding macros during application
-build in order to see the correct variant of the libpng API.  From 1.5.0
-application code can check for the corresponding _SUPPORTED macro:
-
-#ifdef PNG_INCH_CONVERSIONS_SUPPORTED
-   /* code that uses the inch conversion APIs. */
-#endif
-
-This macro will only be defined if the inch conversion functions have been
-compiled into libpng.  The full set of macros, and whether or not support
-has been compiled in, are available in the header file pnglibconf.h.
-This header file is specific to the libpng build.  Notice that prior to
-1.5.0 the _SUPPORTED macros would always have the default definition unless
-reset by pngusr.h or by explicit settings on the compiler command line.
-These settings may produce compiler warnings or errors in 1.5.0 because
-of macro redefinition.
-
-Applications can now choose whether to use these macros or to call the
-corresponding function by defining PNG_USE_READ_MACROS or
-PNG_NO_USE_READ_MACROS before including png.h.  Notice that this is
-only supported from 1.5.0; defining PNG_NO_USE_READ_MACROS prior to 1.5.0
-will lead to a link failure.
-
-Prior to libpng-1.5.4, the zlib compressor used the same set of parameters
-when compressing the IDAT data and textual data such as zTXt and iCCP.
-In libpng-1.5.4 we reinitialized the zlib stream for each type of data.
-We added five png_set_text_*() functions for setting the parameters to
-use with textual data.
-
-Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
-option was off by default, and slightly inaccurate scaling occurred.
-This option can no longer be turned off, and the choice of accurate
-or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8()
-API for accurate scaling or the old png_set_strip_16_to_8() API for simple
-chopping.  In libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
-macro became PNG_READ_SCALE_16_TO_8_SUPPORTED, and the PNG_READ_16_TO_8
-macro became PNG_READ_STRIP_16_TO_8_SUPPORTED, to enable the two
-png_set_*_16_to_8() functions separately.
-
-Prior to libpng-1.5.4, the png_set_user_limits() function could only be
-used to reduce the width and height limits from the value of
-PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said
-that it could be used to override them.  Now this function will reduce or
-increase the limits.
-
-Starting in libpng-1.5.22, default user limits were established. These
-can be overridden by application calls to png_set_user_limits(),
-png_set_user_chunk_cache_max(), and/or png_set_user_malloc_max().
-The limits are now
-                             max possible  default
-   png_user_width_max        0x7fffffff    1,000,000
-   png_user_height_max       0x7fffffff    1,000,000
-   png_user_chunk_cache_max  0 (unlimited) 1000
-   png_user_chunk_malloc_max 0 (unlimited) 8,000,000
-
-The png_set_option() function (and the "options" member of the png struct) was
-added to libpng-1.5.15, with option PNG_ARM_NEON.
-
-The library now supports a complete fixed point implementation and can
-thus be used on systems that have no floating point support or very
-limited or slow support.  Previously gamma correction, an essential part
-of complete PNG support, required reasonably fast floating point.
-
-As part of this the choice of internal implementation has been made
-independent of the choice of fixed versus floating point APIs and all the
-missing fixed point APIs have been implemented.
-
-The exact mechanism used to control attributes of API functions has
-changed, as described in the INSTALL file.
-
-A new test program, pngvalid, is provided in addition to pngtest.
-pngvalid validates the arithmetic accuracy of the gamma correction
-calculations and includes a number of validations of the file format.
-A subset of the full range of tests is run when "make check" is done
-(in the 'configure' build.)  pngvalid also allows total allocated memory
-usage to be evaluated and performs additional memory overwrite validation.
-
-Many changes to individual feature macros have been made. The following
-are the changes most likely to be noticed by library builders who
-configure libpng:
-
-1) All feature macros now have consistent naming:
-
-#define PNG_NO_feature turns the feature off
-#define PNG_feature_SUPPORTED turns the feature on
-
-pnglibconf.h contains one line for each feature macro which is either:
-
-#define PNG_feature_SUPPORTED
-
-if the feature is supported or:
-
-/*#undef PNG_feature_SUPPORTED*/
-
-if it is not.  Library code consistently checks for the 'SUPPORTED' macro.
-It does not, and libpng applications should not, check for the 'NO' macro
-which will not normally be defined even if the feature is not supported.
-The 'NO' macros are only used internally for setting or not setting the
-corresponding 'SUPPORTED' macros.
-
-Compatibility with the old names is provided as follows:
-
-PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED
-
-And the following definitions disable the corresponding feature:
-
-PNG_SETJMP_NOT_SUPPORTED disables SETJMP
-PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS
-PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV
-PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS
-PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS
-PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS
-
-Library builders should remove use of the above, inconsistent, names.
-
-2) Warning and error message formatting was previously conditional on
-the STDIO feature. The library has been changed to use the
-CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled
-the library no longer uses the printf(3) functions, even though the
-default read/write implementations use (FILE) style stdio.h functions.
-
-3) Three feature macros now control the fixed/floating point decisions:
-
-PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs
-
-PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in
-practice these are normally required internally anyway (because the PNG
-file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT
-merely stops the function from being exported.
-
-PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating
-point implementation or the fixed point one.  Typically the fixed point
-implementation is larger and slower than the floating point implementation
-on a system that supports floating point; however, it may be faster on a
-system which lacks floating point hardware and therefore uses a software
-emulation.
-
-4) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED.  This allows the
-functions to read and write ints to be disabled independently of
-PNG_USE_READ_MACROS, which allows libpng to be built with the functions
-even though the default is to use the macros - this allows applications
-to choose at app buildtime whether or not to use macros (previously
-impossible because the functions weren't in the default build.)
-
-XII.  Changes to Libpng from version 1.5.x to 1.6.x
-
-A "simplified API" has been added (see documentation in png.h and a simple
-example in contrib/examples/pngtopng.c).  The new publicly visible API
-includes the following:
-
-   macros:
-     PNG_FORMAT_*
-     PNG_IMAGE_*
-   structures:
-     png_control
-     png_image
-   read functions
-     png_image_begin_read_from_file()
-     png_image_begin_read_from_stdio()
-     png_image_begin_read_from_memory()
-     png_image_finish_read()
-     png_image_free()
-   write functions
-     png_image_write_to_file()
-     png_image_write_to_memory()
-     png_image_write_to_stdio()
-
-Starting with libpng-1.6.0, you can configure libpng to prefix all exported
-symbols, using the PNG_PREFIX macro.
-
-We no longer include string.h in png.h.  The include statement has been moved
-to pngpriv.h, where it is not accessible by applications.  Applications that
-need access to information in string.h must add an '#include <string.h>'
-directive.  It does not matter whether this is placed prior to or after
-the '#include "png.h"' directive.
-
-The following API are now DEPRECATED:
-   png_info_init_3()
-   png_convert_to_rfc1123() which has been replaced
-     with png_convert_to_rfc1123_buffer()
-   png_malloc_default()
-   png_free_default()
-   png_reset_zstream()
-
-The following have been removed:
-   png_get_io_chunk_name(), which has been replaced
-     with png_get_io_chunk_type().  The new
-     function returns a 32-bit integer instead of
-     a string.
-   The png_sizeof(), png_strlen(), png_memcpy(), png_memcmp(), and
-     png_memset() macros are no longer used in the libpng sources and
-     have been removed.  These had already been made invisible to applications
-     (i.e., defined in the private pngpriv.h header file) since libpng-1.5.0.
-
-The signatures of many exported functions were changed, such that
-   png_structp became png_structrp or png_const_structrp
-   png_infop became png_inforp or png_const_inforp
-where "rp" indicates a "restricted pointer".
-
-Dropped support for 16-bit platforms. The support for FAR/far types has
-been eliminated and the definition of png_alloc_size_t is now controlled
-by a flag so that 'small size_t' systems can select it if necessary.
-
-Error detection in some chunks has improved; in particular the iCCP chunk
-reader now does pretty complete validation of the basic format.  Some bad
-profiles that were previously accepted are now accepted with a warning or
-rejected, depending upon the png_set_benign_errors() setting, in particular
-the very old broken Microsoft/HP 3144-byte sRGB profile.  Starting with
-libpng-1.6.11, recognizing and checking sRGB profiles can be avoided by
-means of
-
-    #if defined(PNG_SKIP_sRGB_CHECK_PROFILE) && \
-        defined(PNG_SET_OPTION_SUPPORTED)
-       png_set_option(png_ptr, PNG_SKIP_sRGB_CHECK_PROFILE,
-           PNG_OPTION_ON);
-    #endif
-
-It's not a good idea to do this if you are using the "simplified API",
-which needs to be able to recognize sRGB profiles conveyed via the iCCP
-chunk.
-
-The PNG spec requirement that only grayscale profiles may appear in images
-with color type 0 or 4 and that even if the image only contains gray pixels,
-only RGB profiles may appear in images with color type 2, 3, or 6, is now
-enforced.  The sRGB chunk is allowed to appear in images with any color type
-and is interpreted by libpng to convey a one-tracer-curve gray profile or a
-three-tracer-curve RGB profile as appropriate.
-
-Libpng 1.5.x erroneously used /MD for Debug DLL builds; if you used the debug
-builds in your app and you changed your app to use /MD you will need to
-change it back to /MDd for libpng 1.6.x.
-
-Prior to libpng-1.6.0 a warning would be issued if the iTXt chunk contained
-an empty language field or an empty translated keyword.  Both of these
-are allowed by the PNG specification, so these warnings are no longer issued.
-
-The library now issues an error if the application attempts to set a
-transform after it calls png_read_update_info() or if it attempts to call
-both png_read_update_info() and png_start_read_image() or to call either
-of them more than once.
-
-The default condition for benign_errors is now to treat benign errors as
-warnings while reading and as errors while writing.
-
-The library now issues a warning if both background processing and RGB to
-gray are used when gamma correction happens. As with previous versions of
-the library the results are numerically very incorrect in this case.
-
-There are some minor arithmetic changes in some transforms such as
-png_set_background(), that might be detected by certain regression tests.
-
-Unknown chunk handling has been improved internally, without any API change.
-This adds more correct option control of the unknown handling, corrects
-a pre-existing bug where the per-chunk 'keep' setting is ignored, and makes
-it possible to skip IDAT chunks in the sequential reader.
-
-The machine-generated configure files are no longer included in branches
-libpng16 and later of the GIT repository.  They continue to be included
-in the tarball releases, however.
-
-Libpng-1.6.0 through 1.6.2 used the CMF bytes at the beginning of the IDAT
-stream to set the size of the sliding window for reading instead of using the
-default 32-kbyte sliding window size.  It was discovered that there are
-hundreds of PNG files in the wild that have incorrect CMF bytes that caused
-zlib to issue the "invalid distance too far back" error and reject the file.
-Libpng-1.6.3 and later calculate their own safe CMF from the image dimensions,
-provide a way to revert to the libpng-1.5.x behavior (ignoring the CMF bytes
-and using a 32-kbyte sliding window), by using
-
-    png_set_option(png_ptr, PNG_MAXIMUM_INFLATE_WINDOW,
-        PNG_OPTION_ON);
-
-and provide a tool (contrib/tools/pngfix) for rewriting a PNG file while
-optimizing the CMF bytes in its IDAT chunk correctly.
-
-Libpng-1.6.0 and libpng-1.6.1 wrote uncompressed iTXt chunks with the wrong
-length, which resulted in PNG files that cannot be read beyond the bad iTXt
-chunk.  This error was fixed in libpng-1.6.3, and a tool (called
-contrib/tools/png-fix-itxt) has been added to the libpng distribution.
-
-Starting with libpng-1.6.17, the PNG_SAFE_LIMITS macro was eliminated
-and safe limits are used by default (users who need larger limits
-can still override them at compile time or run time, as described above).
-
-The new limits are
-                                default   spec limit
-   png_user_width_max         1,000,000  2,147,483,647
-   png_user_height_max        1,000,000  2,147,483,647
-   png_user_chunk_cache_max         128  unlimited
-   png_user_chunk_malloc_max  8,000,000  unlimited
-
-Starting with libpng-1.6.18, a PNG_RELEASE_BUILD macro was added, which allows
-library builders to control compilation for an installed system (a release build).
-It can be set for testing debug or beta builds to ensure that they will compile
-when the build type is switched to RC or STABLE. In essence this overrides the
-PNG_LIBPNG_BUILD_BASE_TYPE definition which is not directly user controllable.
-
-Starting with libpng-1.6.19, attempting to set an over-length PLTE chunk
-is an error. Previously this requirement of the PNG specification was not
-enforced, and the palette was always limited to 256 entries. An over-length
-PLTE chunk found in an input PNG is silently truncated.
-
-Starting with libpng-1.6.31, the eXIf chunk is supported. Libpng does not
-attempt to decode the Exif profile; it simply returns a byte array
-containing the profile to the calling application which must do its own
-decoding.
-
-XIII.  Detecting libpng
-
-The png_get_io_ptr() function has been present since libpng-0.88, has never
-changed, and is unaffected by conditional compilation macros.  It is the
-best choice for use in configure scripts for detecting the presence of any
-libpng version since 0.88.  In an autoconf "configure.in" you could use
-
-    AC_CHECK_LIB(png, png_get_io_ptr, ...
-
-XV. Source code repository
-
-Since about February 2009, version 1.2.34, libpng has been under "git" source
-control.  The git repository was built from old libpng-x.y.z.tar.gz files
-going back to version 0.70.  You can access the git repository (read only)
-at
-
-    https://github.com/glennrp/libpng or
-    https://git.code.sf.net/p/libpng/code.git
-
-or you can browse it with a web browser at
-
-    https://github.com/glennrp/libpng or
-    https://sourceforge.net/p/libpng/code/ci/libpng16/tree/
-
-Patches can be sent to glennrp at users.sourceforge.net or to
-png-mng-implement at lists.sourceforge.net or you can upload them to
-the libpng bug tracker at
-
-    https://libpng.sourceforge.io/
-
-or as a "pull request" to
-
-    https://github.com/glennrp/libpng/pulls
-
-We also accept patches built from the tar or zip distributions, and
-simple verbal discriptions of bug fixes, reported either to the
-SourceForge bug tracker, to the png-mng-implement at lists.sf.net
-mailing list, as github issues, or directly to glennrp.
-
-XV. Coding style
-
-Our coding style is similar to the "Allman" style
-(See https://en.wikipedia.org/wiki/Indent_style#Allman_style), with curly
-braces on separate lines:
-
-    if (condition)
-    {
-       action;
-    }
-
-    else if (another condition)
-    {
-       another action;
-    }
-
-The braces can be omitted from simple one-line actions:
-
-    if (condition)
-       return (0);
-
-We use 3-space indentation, except for continued statements which
-are usually indented the same as the first line of the statement
-plus four more spaces.
-
-For macro definitions we use 2-space indentation, always leaving the "#"
-in the first column.
-
-    #ifndef PNG_NO_FEATURE
-    #  ifndef PNG_FEATURE_SUPPORTED
-    #    define PNG_FEATURE_SUPPORTED
-    #  endif
-    #endif
-
-Comments appear with the leading "/*" at the same indentation as
-the statement that follows the comment:
-
-    /* Single-line comment */
-    statement;
-
-    /* This is a multiple-line
-     * comment.
-     */
-    statement;
-
-Very short comments can be placed after the end of the statement
-to which they pertain:
-
-    statement;    /* comment */
-
-We don't use C++ style ("//") comments. We have, however,
-used them in the past in some now-abandoned MMX assembler
-code.
-
-Functions and their curly braces are not indented, and
-exported functions are marked with PNGAPI:
-
- /* This is a public function that is visible to
-  * application programmers. It does thus-and-so.
-  */
- void PNGAPI
- png_exported_function(png_ptr, png_info, foo)
- {
-    body;
- }
-
-The return type and decorations are placed on a separate line
-ahead of the function name, as illustrated above.
-
-The prototypes for all exported functions appear in png.h,
-above the comment that says
-
-    /* Maintainer: Put new public prototypes here ... */
-
-We mark all non-exported functions with "/* PRIVATE */"":
-
- void /* PRIVATE */
- png_non_exported_function(png_ptr, png_info, foo)
- {
-    body;
- }
-
-The prototypes for non-exported functions (except for those in
-pngtest) appear in pngpriv.h above the comment that says
-
-  /* Maintainer: Put new private prototypes here ^ */
-
-To avoid polluting the global namespace, the names of all exported
-functions and variables begin with "png_", and all publicly visible C
-preprocessor macros begin with "PNG".  We request that applications that
-use libpng *not* begin any of their own symbols with either of these strings.
-
-We put a space after the "sizeof" operator and we omit the
-optional parentheses around its argument when the argument
-is an expression, not a type name, and we always enclose the
-sizeof operator, with its argument, in parentheses:
-
-  (sizeof (png_uint_32))
-  (sizeof array)
-
-Prior to libpng-1.6.0 we used a "png_sizeof()" macro, formatted as
-though it were a function.
-
-Control keywords if, for, while, and switch are always followed by a space
-to distinguish them from function calls, which have no trailing space.
-
-We put a space after each comma and after each semicolon
-in "for" statements, and we put spaces before and after each
-C binary operator and after "for" or "while", and before
-"?".  We don't put a space between a typecast and the expression
-being cast, nor do we put one between a function name and the
-left parenthesis that follows it:
-
-    for (i = 2; i > 0; --i)
-       y[i] = a(x) + (int)b;
-
-We prefer #ifdef and #ifndef to #if defined() and #if !defined()
-when there is only one macro being tested.  We always use parentheses
-with "defined".
-
-We express integer constants that are used as bit masks in hex format,
-with an even number of lower-case hex digits, and to make them unsigned
-(e.g., 0x00U, 0xffU, 0x0100U) and long if they are greater than 0x7fff
-(e.g., 0xffffUL).
-
-We prefer to use underscores rather than camelCase in names, except
-for a few type names that we inherit from zlib.h.
-
-We prefer "if (something != 0)" and "if (something == 0)" over
-"if (something)" and if "(!something)", respectively, and for pointers
-we prefer "if (some_pointer != NULL)" or "if (some_pointer == NULL)".
-
-We do not use the TAB character for indentation in the C sources.
-
-Lines do not exceed 80 characters.
-
-Other rules can be inferred by inspecting the libpng source.
-
-XVI. Y2K Compliance in libpng
-
-Since the PNG Development group is an ad-hoc body, we can't make
-an official declaration.
-
-This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.6.34 are Y2K compliant.  It is my belief that earlier
-versions were also Y2K compliant.
-
-Libpng only has two year fields.  One is a 2-byte unsigned integer
-that will hold years up to 65535.  The other, which is deprecated,
-holds the date in text format, and will hold years up to 9999.
-
-The integer is
-    "png_uint_16 year" in png_time_struct.
-
-The string is
-    "char time_buffer[29]" in png_struct.  This is no longer used
-in libpng-1.6.x and will be removed from libpng-1.7.0.
-
-There are seven time-related functions:
-
-    png_convert_to_rfc_1123_buffer() in png.c
-      (formerly png_convert_to_rfc_1152() in error, and
-      also formerly png_convert_to_rfc_1123())
-    png_convert_from_struct_tm() in pngwrite.c, called
-      in pngwrite.c
-    png_convert_from_time_t() in pngwrite.c
-    png_get_tIME() in pngget.c
-    png_handle_tIME() in pngrutil.c, called in pngread.c
-    png_set_tIME() in pngset.c
-    png_write_tIME() in pngwutil.c, called in pngwrite.c
-
-All appear to handle dates properly in a Y2K environment.  The
-png_convert_from_time_t() function calls gmtime() to convert from system
-clock time, which returns (year - 1900), which we properly convert to
-the full 4-digit year.  There is a possibility that applications using
-libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
-function, or that they are incorrectly passing only a 2-digit year
-instead of "year - 1900" into the png_convert_from_struct_tm() function,
-but this is not under our control.  The libpng documentation has always
-stated that it works with 4-digit years, and the APIs have been
-documented as such.
-
-The tIME chunk itself is also Y2K compliant.  It uses a 2-byte unsigned
-integer to hold the year, and can hold years as large as 65535.
-
-zlib, upon which libpng depends, is also Y2K compliant.  It contains
-no date-related code.
-
-
-   Glenn Randers-Pehrson
-   libpng maintainer
-   PNG Development Group