update for zlib & FreeImage

git-svn-id: http://svn.miranda-ng.org/main/trunk@238 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c

1 files changed, 358 insertions, 358 deletions

diff --git a/plugins/FreeImage/Source/LibJPEG/jcprepct.c b/plugins/FreeImage/Source/LibJPEG/jcprepct.c
index 00101e0b57..be44cc4b45 100644
--- a/plugins/FreeImage/Source/LibJPEG/jcprepct.c
+++ b/plugins/FreeImage/Source/LibJPEG/jcprepct.c
@@ -1,358 +1,358 @@
-/*

- * jcprepct.c

- *

- * Copyright (C) 1994-1996, Thomas G. Lane.

- * This file is part of the Independent JPEG Group's software.

- * For conditions of distribution and use, see the accompanying README file.

- *

- * This file contains the compression preprocessing controller.

- * This controller manages the color conversion, downsampling,

- * and edge expansion steps.

- *

- * Most of the complexity here is associated with buffering input rows

- * as required by the downsampler.  See the comments at the head of

- * jcsample.c for the downsampler's needs.

- */

-

-#define JPEG_INTERNALS

-#include "jinclude.h"

-#include "jpeglib.h"

-

-

-/* At present, jcsample.c can request context rows only for smoothing.

- * In the future, we might also need context rows for CCIR601 sampling

- * or other more-complex downsampling procedures.  The code to support

- * context rows should be compiled only if needed.

- */

-#ifdef INPUT_SMOOTHING_SUPPORTED

-#define CONTEXT_ROWS_SUPPORTED

-#endif

-

-

-/*

- * For the simple (no-context-row) case, we just need to buffer one

- * row group's worth of pixels for the downsampling step.  At the bottom of

- * the image, we pad to a full row group by replicating the last pixel row.

- * The downsampler's last output row is then replicated if needed to pad

- * out to a full iMCU row.

- *

- * When providing context rows, we must buffer three row groups' worth of

- * pixels.  Three row groups are physically allocated, but the row pointer

- * arrays are made five row groups high, with the extra pointers above and

- * below "wrapping around" to point to the last and first real row groups.

- * This allows the downsampler to access the proper context rows.

- * At the top and bottom of the image, we create dummy context rows by

- * copying the first or last real pixel row.  This copying could be avoided

- * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the

- * trouble on the compression side.

- */

-

-

-/* Private buffer controller object */

-

-typedef struct {

-  struct jpeg_c_prep_controller pub; /* public fields */

-

-  /* Downsampling input buffer.  This buffer holds color-converted data

-   * until we have enough to do a downsample step.

-   */

-  JSAMPARRAY color_buf[MAX_COMPONENTS];

-

-  JDIMENSION rows_to_go;	/* counts rows remaining in source image */

-  int next_buf_row;		/* index of next row to store in color_buf */

-

-#ifdef CONTEXT_ROWS_SUPPORTED	/* only needed for context case */

-  int this_row_group;		/* starting row index of group to process */

-  int next_buf_stop;		/* downsample when we reach this index */

-#endif

-} my_prep_controller;

-

-typedef my_prep_controller * my_prep_ptr;

-

-

-/*

- * Initialize for a processing pass.

- */

-

-METHODDEF(void)

-start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)

-{

-  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

-

-  if (pass_mode != JBUF_PASS_THRU)

-    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

-

-  /* Initialize total-height counter for detecting bottom of image */

-  prep->rows_to_go = cinfo->image_height;

-  /* Mark the conversion buffer empty */

-  prep->next_buf_row = 0;

-#ifdef CONTEXT_ROWS_SUPPORTED

-  /* Preset additional state variables for context mode.

-   * These aren't used in non-context mode, so we needn't test which mode.

-   */

-  prep->this_row_group = 0;

-  /* Set next_buf_stop to stop after two row groups have been read in. */

-  prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;

-#endif

-}

-

-

-/*

- * Expand an image vertically from height input_rows to height output_rows,

- * by duplicating the bottom row.

- */

-

-LOCAL(void)

-expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,

-		    int input_rows, int output_rows)

-{

-  register int row;

-

-  for (row = input_rows; row < output_rows; row++) {

-    jcopy_sample_rows(image_data, input_rows-1, image_data, row,

-		      1, num_cols);

-  }

-}

-

-

-/*

- * Process some data in the simple no-context case.

- *

- * Preprocessor output data is counted in "row groups".  A row group

- * is defined to be v_samp_factor sample rows of each component.

- * Downsampling will produce this much data from each max_v_samp_factor

- * input rows.

- */

-

-METHODDEF(void)

-pre_process_data (j_compress_ptr cinfo,

-		  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,

-		  JDIMENSION in_rows_avail,

-		  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,

-		  JDIMENSION out_row_groups_avail)

-{

-  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

-  int numrows, ci;

-  JDIMENSION inrows;

-  jpeg_component_info * compptr;

-

-  while (*in_row_ctr < in_rows_avail &&

-	 *out_row_group_ctr < out_row_groups_avail) {

-    /* Do color conversion to fill the conversion buffer. */

-    inrows = in_rows_avail - *in_row_ctr;

-    numrows = cinfo->max_v_samp_factor - prep->next_buf_row;

-    numrows = (int) MIN((JDIMENSION) numrows, inrows);

-    (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,

-				       prep->color_buf,

-				       (JDIMENSION) prep->next_buf_row,

-				       numrows);

-    *in_row_ctr += numrows;

-    prep->next_buf_row += numrows;

-    prep->rows_to_go -= numrows;

-    /* If at bottom of image, pad to fill the conversion buffer. */

-    if (prep->rows_to_go == 0 &&

-	prep->next_buf_row < cinfo->max_v_samp_factor) {

-      for (ci = 0; ci < cinfo->num_components; ci++) {

-	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,

-			   prep->next_buf_row, cinfo->max_v_samp_factor);

-      }

-      prep->next_buf_row = cinfo->max_v_samp_factor;

-    }

-    /* If we've filled the conversion buffer, empty it. */

-    if (prep->next_buf_row == cinfo->max_v_samp_factor) {

-      (*cinfo->downsample->downsample) (cinfo,

-					prep->color_buf, (JDIMENSION) 0,

-					output_buf, *out_row_group_ctr);

-      prep->next_buf_row = 0;

-      (*out_row_group_ctr)++;

-    }

-    /* If at bottom of image, pad the output to a full iMCU height.

-     * Note we assume the caller is providing a one-iMCU-height output buffer!

-     */

-    if (prep->rows_to_go == 0 &&

-	*out_row_group_ctr < out_row_groups_avail) {

-      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

-	   ci++, compptr++) {

-	numrows = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /

-		  cinfo->min_DCT_v_scaled_size;

-	expand_bottom_edge(output_buf[ci],

-			   compptr->width_in_blocks * compptr->DCT_h_scaled_size,

-			   (int) (*out_row_group_ctr * numrows),

-			   (int) (out_row_groups_avail * numrows));

-      }

-      *out_row_group_ctr = out_row_groups_avail;

-      break;			/* can exit outer loop without test */

-    }

-  }

-}

-

-

-#ifdef CONTEXT_ROWS_SUPPORTED

-

-/*

- * Process some data in the context case.

- */

-

-METHODDEF(void)

-pre_process_context (j_compress_ptr cinfo,

-		     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,

-		     JDIMENSION in_rows_avail,

-		     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,

-		     JDIMENSION out_row_groups_avail)

-{

-  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

-  int numrows, ci;

-  int buf_height = cinfo->max_v_samp_factor * 3;

-  JDIMENSION inrows;

-

-  while (*out_row_group_ctr < out_row_groups_avail) {

-    if (*in_row_ctr < in_rows_avail) {

-      /* Do color conversion to fill the conversion buffer. */

-      inrows = in_rows_avail - *in_row_ctr;

-      numrows = prep->next_buf_stop - prep->next_buf_row;

-      numrows = (int) MIN((JDIMENSION) numrows, inrows);

-      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,

-					 prep->color_buf,

-					 (JDIMENSION) prep->next_buf_row,

-					 numrows);

-      /* Pad at top of image, if first time through */

-      if (prep->rows_to_go == cinfo->image_height) {

-	for (ci = 0; ci < cinfo->num_components; ci++) {

-	  int row;

-	  for (row = 1; row <= cinfo->max_v_samp_factor; row++) {

-	    jcopy_sample_rows(prep->color_buf[ci], 0,

-			      prep->color_buf[ci], -row,

-			      1, cinfo->image_width);

-	  }

-	}

-      }

-      *in_row_ctr += numrows;

-      prep->next_buf_row += numrows;

-      prep->rows_to_go -= numrows;

-    } else {

-      /* Return for more data, unless we are at the bottom of the image. */

-      if (prep->rows_to_go != 0)

-	break;

-      /* When at bottom of image, pad to fill the conversion buffer. */

-      if (prep->next_buf_row < prep->next_buf_stop) {

-	for (ci = 0; ci < cinfo->num_components; ci++) {

-	  expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,

-			     prep->next_buf_row, prep->next_buf_stop);

-	}

-	prep->next_buf_row = prep->next_buf_stop;

-      }

-    }

-    /* If we've gotten enough data, downsample a row group. */

-    if (prep->next_buf_row == prep->next_buf_stop) {

-      (*cinfo->downsample->downsample) (cinfo,

-					prep->color_buf,

-					(JDIMENSION) prep->this_row_group,

-					output_buf, *out_row_group_ctr);

-      (*out_row_group_ctr)++;

-      /* Advance pointers with wraparound as necessary. */

-      prep->this_row_group += cinfo->max_v_samp_factor;

-      if (prep->this_row_group >= buf_height)

-	prep->this_row_group = 0;

-      if (prep->next_buf_row >= buf_height)

-	prep->next_buf_row = 0;

-      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;

-    }

-  }

-}

-

-

-/*

- * Create the wrapped-around downsampling input buffer needed for context mode.

- */

-

-LOCAL(void)

-create_context_buffer (j_compress_ptr cinfo)

-{

-  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

-  int rgroup_height = cinfo->max_v_samp_factor;

-  int ci, i;

-  jpeg_component_info * compptr;

-  JSAMPARRAY true_buffer, fake_buffer;

-

-  /* Grab enough space for fake row pointers for all the components;

-   * we need five row groups' worth of pointers for each component.

-   */

-  fake_buffer = (JSAMPARRAY)

-    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

-				(cinfo->num_components * 5 * rgroup_height) *

-				SIZEOF(JSAMPROW));

-

-  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

-       ci++, compptr++) {

-    /* Allocate the actual buffer space (3 row groups) for this component.

-     * We make the buffer wide enough to allow the downsampler to edge-expand

-     * horizontally within the buffer, if it so chooses.

-     */

-    true_buffer = (*cinfo->mem->alloc_sarray)

-      ((j_common_ptr) cinfo, JPOOL_IMAGE,

-       (JDIMENSION) (((long) compptr->width_in_blocks *

-		      cinfo->min_DCT_h_scaled_size *

-		      cinfo->max_h_samp_factor) / compptr->h_samp_factor),

-       (JDIMENSION) (3 * rgroup_height));

-    /* Copy true buffer row pointers into the middle of the fake row array */

-    MEMCOPY(fake_buffer + rgroup_height, true_buffer,

-	    3 * rgroup_height * SIZEOF(JSAMPROW));

-    /* Fill in the above and below wraparound pointers */

-    for (i = 0; i < rgroup_height; i++) {

-      fake_buffer[i] = true_buffer[2 * rgroup_height + i];

-      fake_buffer[4 * rgroup_height + i] = true_buffer[i];

-    }

-    prep->color_buf[ci] = fake_buffer + rgroup_height;

-    fake_buffer += 5 * rgroup_height; /* point to space for next component */

-  }

-}

-

-#endif /* CONTEXT_ROWS_SUPPORTED */

-

-

-/*

- * Initialize preprocessing controller.

- */

-

-GLOBAL(void)

-jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)

-{

-  my_prep_ptr prep;

-  int ci;

-  jpeg_component_info * compptr;

-

-  if (need_full_buffer)		/* safety check */

-    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

-

-  prep = (my_prep_ptr)

-    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

-				SIZEOF(my_prep_controller));

-  cinfo->prep = (struct jpeg_c_prep_controller *) prep;

-  prep->pub.start_pass = start_pass_prep;

-

-  /* Allocate the color conversion buffer.

-   * We make the buffer wide enough to allow the downsampler to edge-expand

-   * horizontally within the buffer, if it so chooses.

-   */

-  if (cinfo->downsample->need_context_rows) {

-    /* Set up to provide context rows */

-#ifdef CONTEXT_ROWS_SUPPORTED

-    prep->pub.pre_process_data = pre_process_context;

-    create_context_buffer(cinfo);

-#else

-    ERREXIT(cinfo, JERR_NOT_COMPILED);

-#endif

-  } else {

-    /* No context, just make it tall enough for one row group */

-    prep->pub.pre_process_data = pre_process_data;

-    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

-	 ci++, compptr++) {

-      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)

-	((j_common_ptr) cinfo, JPOOL_IMAGE,

-	 (JDIMENSION) (((long) compptr->width_in_blocks *

-			cinfo->min_DCT_h_scaled_size *

-			cinfo->max_h_samp_factor) / compptr->h_samp_factor),

-	 (JDIMENSION) cinfo->max_v_samp_factor);

-    }

-  }

-}

+/*
+ * jcprepct.c
+ *
+ * Copyright (C) 1994-1996, Thomas G. Lane.
+ * This file is part of the Independent JPEG Group's software.
+ * For conditions of distribution and use, see the accompanying README file.
+ *
+ * This file contains the compression preprocessing controller.
+ * This controller manages the color conversion, downsampling,
+ * and edge expansion steps.
+ *
+ * Most of the complexity here is associated with buffering input rows
+ * as required by the downsampler.  See the comments at the head of
+ * jcsample.c for the downsampler's needs.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+
+
+/* At present, jcsample.c can request context rows only for smoothing.
+ * In the future, we might also need context rows for CCIR601 sampling
+ * or other more-complex downsampling procedures.  The code to support
+ * context rows should be compiled only if needed.
+ */
+#ifdef INPUT_SMOOTHING_SUPPORTED
+#define CONTEXT_ROWS_SUPPORTED
+#endif
+
+
+/*
+ * For the simple (no-context-row) case, we just need to buffer one
+ * row group's worth of pixels for the downsampling step.  At the bottom of
+ * the image, we pad to a full row group by replicating the last pixel row.
+ * The downsampler's last output row is then replicated if needed to pad
+ * out to a full iMCU row.
+ *
+ * When providing context rows, we must buffer three row groups' worth of
+ * pixels.  Three row groups are physically allocated, but the row pointer
+ * arrays are made five row groups high, with the extra pointers above and
+ * below "wrapping around" to point to the last and first real row groups.
+ * This allows the downsampler to access the proper context rows.
+ * At the top and bottom of the image, we create dummy context rows by
+ * copying the first or last real pixel row.  This copying could be avoided
+ * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
+ * trouble on the compression side.
+ */
+
+
+/* Private buffer controller object */
+
+typedef struct {
+  struct jpeg_c_prep_controller pub; /* public fields */
+
+  /* Downsampling input buffer.  This buffer holds color-converted data
+   * until we have enough to do a downsample step.
+   */
+  JSAMPARRAY color_buf[MAX_COMPONENTS];
+
+  JDIMENSION rows_to_go;	/* counts rows remaining in source image */
+  int next_buf_row;		/* index of next row to store in color_buf */
+
+#ifdef CONTEXT_ROWS_SUPPORTED	/* only needed for context case */
+  int this_row_group;		/* starting row index of group to process */
+  int next_buf_stop;		/* downsample when we reach this index */
+#endif
+} my_prep_controller;
+
+typedef my_prep_controller * my_prep_ptr;
+
+
+/*
+ * Initialize for a processing pass.
+ */
+
+METHODDEF(void)
+start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
+{
+  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
+
+  if (pass_mode != JBUF_PASS_THRU)
+    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
+
+  /* Initialize total-height counter for detecting bottom of image */
+  prep->rows_to_go = cinfo->image_height;
+  /* Mark the conversion buffer empty */
+  prep->next_buf_row = 0;
+#ifdef CONTEXT_ROWS_SUPPORTED
+  /* Preset additional state variables for context mode.
+   * These aren't used in non-context mode, so we needn't test which mode.
+   */
+  prep->this_row_group = 0;
+  /* Set next_buf_stop to stop after two row groups have been read in. */
+  prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
+#endif
+}
+
+
+/*
+ * Expand an image vertically from height input_rows to height output_rows,
+ * by duplicating the bottom row.
+ */
+
+LOCAL(void)
+expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
+		    int input_rows, int output_rows)
+{
+  register int row;
+
+  for (row = input_rows; row < output_rows; row++) {
+    jcopy_sample_rows(image_data, input_rows-1, image_data, row,
+		      1, num_cols);
+  }
+}
+
+
+/*
+ * Process some data in the simple no-context case.
+ *
+ * Preprocessor output data is counted in "row groups".  A row group
+ * is defined to be v_samp_factor sample rows of each component.
+ * Downsampling will produce this much data from each max_v_samp_factor
+ * input rows.
+ */
+
+METHODDEF(void)
+pre_process_data (j_compress_ptr cinfo,
+		  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
+		  JDIMENSION in_rows_avail,
+		  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
+		  JDIMENSION out_row_groups_avail)
+{
+  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
+  int numrows, ci;
+  JDIMENSION inrows;
+  jpeg_component_info * compptr;
+
+  while (*in_row_ctr < in_rows_avail &&
+	 *out_row_group_ctr < out_row_groups_avail) {
+    /* Do color conversion to fill the conversion buffer. */
+    inrows = in_rows_avail - *in_row_ctr;
+    numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
+    numrows = (int) MIN((JDIMENSION) numrows, inrows);
+    (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
+				       prep->color_buf,
+				       (JDIMENSION) prep->next_buf_row,
+				       numrows);
+    *in_row_ctr += numrows;
+    prep->next_buf_row += numrows;
+    prep->rows_to_go -= numrows;
+    /* If at bottom of image, pad to fill the conversion buffer. */
+    if (prep->rows_to_go == 0 &&
+	prep->next_buf_row < cinfo->max_v_samp_factor) {
+      for (ci = 0; ci < cinfo->num_components; ci++) {
+	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
+			   prep->next_buf_row, cinfo->max_v_samp_factor);
+      }
+      prep->next_buf_row = cinfo->max_v_samp_factor;
+    }
+    /* If we've filled the conversion buffer, empty it. */
+    if (prep->next_buf_row == cinfo->max_v_samp_factor) {
+      (*cinfo->downsample->downsample) (cinfo,
+					prep->color_buf, (JDIMENSION) 0,
+					output_buf, *out_row_group_ctr);
+      prep->next_buf_row = 0;
+      (*out_row_group_ctr)++;
+    }
+    /* If at bottom of image, pad the output to a full iMCU height.
+     * Note we assume the caller is providing a one-iMCU-height output buffer!
+     */
+    if (prep->rows_to_go == 0 &&
+	*out_row_group_ctr < out_row_groups_avail) {
+      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+	   ci++, compptr++) {
+	numrows = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
+		  cinfo->min_DCT_v_scaled_size;
+	expand_bottom_edge(output_buf[ci],
+			   compptr->width_in_blocks * compptr->DCT_h_scaled_size,
+			   (int) (*out_row_group_ctr * numrows),
+			   (int) (out_row_groups_avail * numrows));
+      }
+      *out_row_group_ctr = out_row_groups_avail;
+      break;			/* can exit outer loop without test */
+    }
+  }
+}
+
+
+#ifdef CONTEXT_ROWS_SUPPORTED
+
+/*
+ * Process some data in the context case.
+ */
+
+METHODDEF(void)
+pre_process_context (j_compress_ptr cinfo,
+		     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
+		     JDIMENSION in_rows_avail,
+		     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
+		     JDIMENSION out_row_groups_avail)
+{
+  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
+  int numrows, ci;
+  int buf_height = cinfo->max_v_samp_factor * 3;
+  JDIMENSION inrows;
+
+  while (*out_row_group_ctr < out_row_groups_avail) {
+    if (*in_row_ctr < in_rows_avail) {
+      /* Do color conversion to fill the conversion buffer. */
+      inrows = in_rows_avail - *in_row_ctr;
+      numrows = prep->next_buf_stop - prep->next_buf_row;
+      numrows = (int) MIN((JDIMENSION) numrows, inrows);
+      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
+					 prep->color_buf,
+					 (JDIMENSION) prep->next_buf_row,
+					 numrows);
+      /* Pad at top of image, if first time through */
+      if (prep->rows_to_go == cinfo->image_height) {
+	for (ci = 0; ci < cinfo->num_components; ci++) {
+	  int row;
+	  for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
+	    jcopy_sample_rows(prep->color_buf[ci], 0,
+			      prep->color_buf[ci], -row,
+			      1, cinfo->image_width);
+	  }
+	}
+      }
+      *in_row_ctr += numrows;
+      prep->next_buf_row += numrows;
+      prep->rows_to_go -= numrows;
+    } else {
+      /* Return for more data, unless we are at the bottom of the image. */
+      if (prep->rows_to_go != 0)
+	break;
+      /* When at bottom of image, pad to fill the conversion buffer. */
+      if (prep->next_buf_row < prep->next_buf_stop) {
+	for (ci = 0; ci < cinfo->num_components; ci++) {
+	  expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
+			     prep->next_buf_row, prep->next_buf_stop);
+	}
+	prep->next_buf_row = prep->next_buf_stop;
+      }
+    }
+    /* If we've gotten enough data, downsample a row group. */
+    if (prep->next_buf_row == prep->next_buf_stop) {
+      (*cinfo->downsample->downsample) (cinfo,
+					prep->color_buf,
+					(JDIMENSION) prep->this_row_group,
+					output_buf, *out_row_group_ctr);
+      (*out_row_group_ctr)++;
+      /* Advance pointers with wraparound as necessary. */
+      prep->this_row_group += cinfo->max_v_samp_factor;
+      if (prep->this_row_group >= buf_height)
+	prep->this_row_group = 0;
+      if (prep->next_buf_row >= buf_height)
+	prep->next_buf_row = 0;
+      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
+    }
+  }
+}
+
+
+/*
+ * Create the wrapped-around downsampling input buffer needed for context mode.
+ */
+
+LOCAL(void)
+create_context_buffer (j_compress_ptr cinfo)
+{
+  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
+  int rgroup_height = cinfo->max_v_samp_factor;
+  int ci, i;
+  jpeg_component_info * compptr;
+  JSAMPARRAY true_buffer, fake_buffer;
+
+  /* Grab enough space for fake row pointers for all the components;
+   * we need five row groups' worth of pointers for each component.
+   */
+  fake_buffer = (JSAMPARRAY)
+    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+				(cinfo->num_components * 5 * rgroup_height) *
+				SIZEOF(JSAMPROW));
+
+  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+       ci++, compptr++) {
+    /* Allocate the actual buffer space (3 row groups) for this component.
+     * We make the buffer wide enough to allow the downsampler to edge-expand
+     * horizontally within the buffer, if it so chooses.
+     */
+    true_buffer = (*cinfo->mem->alloc_sarray)
+      ((j_common_ptr) cinfo, JPOOL_IMAGE,
+       (JDIMENSION) (((long) compptr->width_in_blocks *
+		      cinfo->min_DCT_h_scaled_size *
+		      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
+       (JDIMENSION) (3 * rgroup_height));
+    /* Copy true buffer row pointers into the middle of the fake row array */
+    MEMCOPY(fake_buffer + rgroup_height, true_buffer,
+	    3 * rgroup_height * SIZEOF(JSAMPROW));
+    /* Fill in the above and below wraparound pointers */
+    for (i = 0; i < rgroup_height; i++) {
+      fake_buffer[i] = true_buffer[2 * rgroup_height + i];
+      fake_buffer[4 * rgroup_height + i] = true_buffer[i];
+    }
+    prep->color_buf[ci] = fake_buffer + rgroup_height;
+    fake_buffer += 5 * rgroup_height; /* point to space for next component */
+  }
+}
+
+#endif /* CONTEXT_ROWS_SUPPORTED */
+
+
+/*
+ * Initialize preprocessing controller.
+ */
+
+GLOBAL(void)
+jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
+{
+  my_prep_ptr prep;
+  int ci;
+  jpeg_component_info * compptr;
+
+  if (need_full_buffer)		/* safety check */
+    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
+
+  prep = (my_prep_ptr)
+    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+				SIZEOF(my_prep_controller));
+  cinfo->prep = (struct jpeg_c_prep_controller *) prep;
+  prep->pub.start_pass = start_pass_prep;
+
+  /* Allocate the color conversion buffer.
+   * We make the buffer wide enough to allow the downsampler to edge-expand
+   * horizontally within the buffer, if it so chooses.
+   */
+  if (cinfo->downsample->need_context_rows) {
+    /* Set up to provide context rows */
+#ifdef CONTEXT_ROWS_SUPPORTED
+    prep->pub.pre_process_data = pre_process_context;
+    create_context_buffer(cinfo);
+#else
+    ERREXIT(cinfo, JERR_NOT_COMPILED);
+#endif
+  } else {
+    /* No context, just make it tall enough for one row group */
+    prep->pub.pre_process_data = pre_process_data;
+    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+	 ci++, compptr++) {
+      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
+	((j_common_ptr) cinfo, JPOOL_IMAGE,
+	 (JDIMENSION) (((long) compptr->width_in_blocks *
+			cinfo->min_DCT_h_scaled_size *
+			cinfo->max_h_samp_factor) / compptr->h_samp_factor),
+	 (JDIMENSION) cinfo->max_v_samp_factor);
+    }
+  }
+}