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agg_arc.cpp
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agg_arc.cpp
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//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
// mcseemagg@yahoo.com
// http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Arc vertex generator
//
//----------------------------------------------------------------------------
#include <math.h>
#include "agg_arc.h"
namespace agg
{
//------------------------------------------------------------------------
arc::arc(double x, double y,
double rx, double ry,
double a1, double a2,
bool ccw) :
m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0)
{
normalize(a1, a2, ccw);
}
//------------------------------------------------------------------------
void arc::init(double x, double y,
double rx, double ry,
double a1, double a2,
bool ccw)
{
m_x = x; m_y = y;
m_rx = rx; m_ry = ry;
normalize(a1, a2, ccw);
}
//------------------------------------------------------------------------
void arc::approximation_scale(double s)
{
m_scale = s;
if(m_initialized)
{
normalize(m_start, m_end, m_ccw);
}
}
//------------------------------------------------------------------------
void arc::rewind(unsigned)
{
m_path_cmd = path_cmd_move_to;
m_angle = m_start;
}
//------------------------------------------------------------------------
unsigned arc::vertex(double* x, double* y)
{
if(is_stop(m_path_cmd)) return path_cmd_stop;
if((m_angle < m_end - m_da/4) != m_ccw)
{
*x = m_x + cos(m_end) * m_rx;
*y = m_y + sin(m_end) * m_ry;
m_path_cmd = path_cmd_stop;
return path_cmd_line_to;
}
*x = m_x + cos(m_angle) * m_rx;
*y = m_y + sin(m_angle) * m_ry;
m_angle += m_da;
unsigned pf = m_path_cmd;
m_path_cmd = path_cmd_line_to;
return pf;
}
//------------------------------------------------------------------------
void arc::normalize(double a1, double a2, bool ccw)
{
double ra = (fabs(m_rx) + fabs(m_ry)) / 2;
m_da = acos(ra / (ra + 0.125 / m_scale)) * 2;
if(ccw)
{
while(a2 < a1) a2 += pi * 2.0;
}
else
{
while(a1 < a2) a1 += pi * 2.0;
m_da = -m_da;
}
m_ccw = ccw;
m_start = a1;
m_end = a2;
m_initialized = true;
}
}