headers/libs/agg/agg_ellipse_bresenham.h

   1 //----------------------------------------------------------------------------
   2 // Anti-Grain Geometry - Version 2.4
   3 // Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
   4 //
   5 // Permission to copy, use, modify, sell and distribute this software
   6 // is granted provided this copyright notice appears in all copies.
   7 // This software is provided "as is" without express or implied
   8 // warranty, and with no claim as to its suitability for any purpose.
   9 //
  10 //----------------------------------------------------------------------------
  11 // Contact: mcseem@antigrain.com
  12 //          mcseemagg@yahoo.com
  13 //          http://www.antigrain.com
  14 //----------------------------------------------------------------------------
  15 //
  16 // Simple Bresenham interpolator for ellipsees
  17 //
  18 //----------------------------------------------------------------------------
  19
  20 #ifndef AGG_ELLIPSE_BRESENHAM_INCLUDED
  21 #define AGG_ELLIPSE_BRESENHAM_INCLUDED
  22
  23
  24 #include "agg_basics.h"
  25
  26
  27 namespace agg
  28 {
  29
  30     //------------------------------------------ellipse_bresenham_interpolator
  31     class ellipse_bresenham_interpolator
  32     {
  33     public:
  34         ellipse_bresenham_interpolator(int rx, int ry) :
  35             m_rx2(rx * rx),
  36             m_ry2(ry * ry),
  37             m_two_rx2(m_rx2 << 1),
  38             m_two_ry2(m_ry2 << 1),
  39             m_dx(0),
  40             m_dy(0),
  41             m_inc_x(0),
  42             m_inc_y(-ry * m_two_rx2),
  43             m_cur_f(0)
  44         {}
  45
  46         int dx() const { return m_dx; }
  47         int dy() const { return m_dy; }
  48
  49         void operator++ ()
  50         {
  51             int  mx, my, mxy, min_m;
  52             int  fx, fy, fxy;
  53
  54             mx = fx = m_cur_f + m_inc_x + m_ry2;
  55             if(mx < 0) mx = -mx;
  56
  57             my = fy = m_cur_f + m_inc_y + m_rx2;
  58             if(my < 0) my = -my;
  59
  60             mxy = fxy = m_cur_f + m_inc_x + m_ry2 + m_inc_y + m_rx2;
  61             if(mxy < 0) mxy = -mxy;
  62
  63             min_m = mx;
  64             bool flag = true;
  65
  66             if(min_m > my)
  67             {
  68                 min_m = my;
  69                 flag = false;
  70             }
  71
  72             m_dx = m_dy = 0;
  73
  74             if(min_m > mxy)
  75             {
  76                 m_inc_x += m_two_ry2;
  77                 m_inc_y += m_two_rx2;
  78                 m_cur_f = fxy;
  79                 m_dx = 1;
  80                 m_dy = 1;
  81                 return;
  82             }
  83
  84             if(flag)
  85             {
  86                 m_inc_x += m_two_ry2;
  87                 m_cur_f = fx;
  88                 m_dx = 1;
  89                 return;
  90             }
  91
  92             m_inc_y += m_two_rx2;
  93             m_cur_f = fy;
  94             m_dy = 1;
  95         }
  96
  97     private:
  98         int m_rx2;
  99         int m_ry2;
 100         int m_two_rx2;
 101         int m_two_ry2;
 102         int m_dx;
 103         int m_dy;
 104         int m_inc_x;
 105         int m_inc_y;
 106         int m_cur_f;
 107
 108     };
 109
 110 }
 111
 112 #endif
 113