Anti-Grain Geometry Tutorial
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 
agg::ellipse_bresenham_interpolator
Definition: agg_ellipse_bresenham.h:31
agg
Definition: agg_arc.cpp:24