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//----------------------------------------------------------------------------
// Anti-Grain Geometry (AGG) - Version 2.5
// A high quality rendering engine for C++
// Copyright (C) 2002-2006 Maxim Shemanarev
// Contact: mcseem@antigrain.com
// mcseemagg@yahoo.com
// http://antigrain.com
//
// AGG is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// AGG is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with AGG; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
// MA 02110-1301, USA.
//----------------------------------------------------------------------------
#ifndef AGG_ELLIPSE_INCLUDED
#define AGG_ELLIPSE_INCLUDED
#include "agg_basics.h"
#include <math.h>
namespace agg
{
//----------------------------------------------------------------ellipse
class ellipse
{
public:
ellipse() :
m_x(0.0), m_y(0.0), m_rx(1.0), m_ry(1.0), m_scale(1.0),
m_num(4), m_step(0), m_cw(false) {}
ellipse(double x, double y, double rx, double ry,
unsigned num_steps=0, bool cw=false) :
m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0),
m_num(num_steps), m_step(0), m_cw(cw)
{
if(m_num == 0) calc_num_steps();
}
void init(double x, double y, double rx, double ry,
unsigned num_steps=0, bool cw=false);
void approximation_scale(double scale);
void rewind(unsigned path_id);
unsigned vertex(double* x, double* y);
private:
void calc_num_steps();
double m_x;
double m_y;
double m_rx;
double m_ry;
double m_scale;
unsigned m_num;
unsigned m_step;
bool m_cw;
};
//------------------------------------------------------------------------
inline void ellipse::init(double x, double y, double rx, double ry,
unsigned num_steps, bool cw)
{
m_x = x;
m_y = y;
m_rx = rx;
m_ry = ry;
m_num = num_steps;
m_step = 0;
m_cw = cw;
if(m_num == 0) calc_num_steps();
}
//------------------------------------------------------------------------
inline void ellipse::approximation_scale(double scale)
{
m_scale = scale;
calc_num_steps();
}
//------------------------------------------------------------------------
inline void ellipse::calc_num_steps()
{
double ra = (fabs(m_rx) + fabs(m_ry)) / 2;
double da = acos(ra / (ra + 0.125 / m_scale)) * 2;
m_num = uround(2*pi / da);
}
//------------------------------------------------------------------------
inline void ellipse::rewind(unsigned)
{
m_step = 0;
}
//------------------------------------------------------------------------
inline unsigned ellipse::vertex(double* x, double* y)
{
if(m_step == m_num)
{
++m_step;
return path_cmd_end_poly | path_flags_close | path_flags_ccw;
}
if(m_step > m_num) return path_cmd_stop;
double angle = double(m_step) / double(m_num) * 2.0 * pi;
if(m_cw) angle = 2.0 * pi - angle;
*x = m_x + cos(angle) * m_rx;
*y = m_y + sin(angle) * m_ry;
m_step++;
return ((m_step == 1) ? path_cmd_move_to : path_cmd_line_to);
}
}
#endif
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