headers/libs/agg/agg_ellipse.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 // class ellipse
  17 //
  18 //----------------------------------------------------------------------------
  19
  20 #ifndef AGG_ELLIPSE_INCLUDED
  21 #define AGG_ELLIPSE_INCLUDED
  22
  23 #include "agg_basics.h"
  24 #include <math.h>
  25
  26 namespace agg
  27 {
  28
  29     //----------------------------------------------------------------ellipse
  30     class ellipse
  31     {
  32     public:
  33         ellipse() :
  34             m_x(0.0), m_y(0.0), m_rx(1.0), m_ry(1.0), m_scale(1.0),
  35             m_num(4), m_step(0), m_cw(false) {}
  36
  37         ellipse(double x, double y, double rx, double ry,
  38                 unsigned num_steps=0, bool cw=false) :
  39             m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0),
  40             m_num(num_steps), m_step(0), m_cw(cw)
  41         {
  42             if(m_num == 0) calc_num_steps();
  43         }
  44
  45         void init(double x, double y, double rx, double ry,
  46                   unsigned num_steps=0, bool cw=false);
  47
  48         void approximation_scale(double scale);
  49         void rewind(unsigned path_id);
  50         unsigned vertex(double* x, double* y);
  51
  52     private:
  53         void calc_num_steps();
  54
  55         double m_x;
  56         double m_y;
  57         double m_rx;
  58         double m_ry;
  59         double m_scale;
  60         unsigned m_num;
  61         unsigned m_step;
  62         bool m_cw;
  63     };
  64
  65     //------------------------------------------------------------------------
  66     inline void ellipse::init(double x, double y, double rx, double ry,
  67                               unsigned num_steps, bool cw)
  68     {
  69         m_x = x;
  70         m_y = y;
  71         m_rx = rx;
  72         m_ry = ry;
  73         m_num = num_steps;
  74         m_step = 0;
  75         m_cw = cw;
  76         if(m_num == 0) calc_num_steps();
  77     }
  78
  79     //------------------------------------------------------------------------
  80     inline void ellipse::approximation_scale(double scale)
  81     {
  82         m_scale = scale;
  83         calc_num_steps();
  84     }
  85
  86     //------------------------------------------------------------------------
  87     inline void ellipse::calc_num_steps()
  88     {
  89         double ra = (fabs(m_rx) + fabs(m_ry)) / 2;
  90         double da = acos(ra / (ra + 0.125 / m_scale)) * 2;
  91         m_num = uround(2*pi / da);
  92     }
  93
  94     //------------------------------------------------------------------------
  95     inline void ellipse::rewind(unsigned)
  96     {
  97         m_step = 0;
  98     }
  99
 100     //------------------------------------------------------------------------
 101     inline unsigned ellipse::vertex(double* x, double* y)
 102     {
 103         if(m_step == m_num)
 104         {
 105             ++m_step;
 106             return path_cmd_end_poly | path_flags_close | path_flags_ccw;
 107         }
 108         if(m_step > m_num) return path_cmd_stop;
 109         double angle = double(m_step) / double(m_num) * 2.0 * pi;
 110         if(m_cw) angle = 2.0 * pi - angle;
 111         *x = m_x + cos(angle) * m_rx;
 112         *y = m_y + sin(angle) * m_ry;
 113         m_step++;
 114         return ((m_step == 1) ? path_cmd_move_to : path_cmd_line_to);
 115     }
 116
 117 }
 118
 119
 120
 121 #endif
 122
 123