agg/inc/agg_ellipse.h

   1 //----------------------------------------------------------------------------
   2 // Anti-Grain Geometry - Version 2.3
   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() : m_x(0.0), m_y(0.0), m_rx(1.0), m_ry(1.0), m_num(4), m_step(0) {}
  34         ellipse(double x, double y, double rx, double ry, unsigned num_steps)
  35             : m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_num(num_steps), m_step(0) {}
  36
  37         void init(double x, double y, double rx, double ry, unsigned num_steps);
  38         void approximation_scale(double scale);
  39         void rewind(unsigned id);
  40         unsigned vertex(double* x, double* y);
  41
  42     private:
  43         double m_x;
  44         double m_y;
  45         double m_rx;
  46         double m_ry;
  47         unsigned m_num;
  48         unsigned m_step;
  49     };
  50
  51
  52     //------------------------------------------------------------------------
  53     inline void ellipse::init(double x, double y, double rx, double ry, unsigned num_steps)
  54     {
  55         m_x = x;
  56         m_y = y;
  57         m_rx = rx;
  58         m_ry = ry;
  59         m_num = num_steps;
  60         m_step = 0;
  61     }
  62
  63     //------------------------------------------------------------------------
  64     inline void ellipse::approximation_scale(double scale)
  65     {
  66        m_num = unsigned((fabs(m_rx) + fabs(m_ry) + 6.0) * scale);
  67        if(m_num < 6) m_num = 6;
  68     }
  69
  70     //------------------------------------------------------------------------
  71     inline void ellipse::rewind(unsigned)
  72     {
  73         m_step = 0;
  74     }
  75
  76     //------------------------------------------------------------------------
  77     inline unsigned ellipse::vertex(double* x, double* y)
  78     {
  79         if(m_step == m_num)
  80         {
  81             ++m_step;
  82             return path_cmd_end_poly | path_flags_close | path_flags_ccw;
  83         }
  84         if(m_step > m_num) return path_cmd_stop;
  85         double angle = double(m_step) / double(m_num) * 2.0 * pi;
  86         *x = m_x + cos(angle) * m_rx;
  87         *y = m_y + sin(angle) * m_ry;
  88         m_step++;
  89         return ((m_step == 1) ? path_cmd_move_to : path_cmd_line_to);
  90     }
  91
  92 }
  93
  94
  95
  96 #endif
  97
  98