agg/source/agg_arc.cpp

   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 // Arc vertex generator
  17 //
  18 //----------------------------------------------------------------------------
  19
  20 #include <math.h>
  21 #include "agg_arc.h"
  22
  23
  24 namespace agg
  25 {
  26     //------------------------------------------------------------------------
  27     arc::arc(double x,  double y,
  28              double rx, double ry,
  29              double a1, double a2,
  30              bool ccw) :
  31         m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0)
  32     {
  33         normalize(a1, a2, ccw);
  34     }
  35
  36     //------------------------------------------------------------------------
  37     void arc::init(double x,  double y,
  38                    double rx, double ry,
  39                    double a1, double a2,
  40                    bool ccw)
  41     {
  42         m_x   = x;  m_y  = y;
  43         m_rx  = rx; m_ry = ry;
  44         normalize(a1, a2, ccw);
  45     }
  46
  47     //------------------------------------------------------------------------
  48     void arc::approximation_scale(double s)
  49     {
  50         m_scale = s;
  51         if(m_initialized)
  52         {
  53             normalize(m_start, m_end, m_ccw);
  54         }
  55     }
  56
  57     //------------------------------------------------------------------------
  58     void arc::rewind(unsigned)
  59     {
  60         m_path_cmd = path_cmd_move_to;
  61         m_angle = m_start;
  62     }
  63
  64     //------------------------------------------------------------------------
  65     unsigned arc::vertex(double* x, double* y)
  66     {
  67         if(is_stop(m_path_cmd)) return path_cmd_stop;
  68         if((m_angle < m_end) != m_ccw)
  69         {
  70             *x = m_x + cos(m_end) * m_rx;
  71             *y = m_y + sin(m_end) * m_ry;
  72             m_path_cmd = path_cmd_stop;
  73             return path_cmd_line_to;
  74         }
  75
  76         *x = m_x + cos(m_angle) * m_rx;
  77         *y = m_y + sin(m_angle) * m_ry;
  78
  79         m_angle += m_da;
  80
  81         unsigned pf = m_path_cmd;
  82         m_path_cmd = path_cmd_line_to;
  83         return pf;
  84     }
  85
  86     //------------------------------------------------------------------------
  87     void arc::normalize(double a1, double a2, bool ccw)
  88     {
  89         m_da = fabs(1.0 / ((m_rx + m_ry) * 0.5 * m_scale));
  90         if(ccw)
  91         {
  92             while(a2 < a1) a2 += pi * 2.0;
  93         }
  94         else
  95         {
  96             while(a1 < a2) a1 += pi * 2.0;
  97             m_da = -m_da;
  98         }
  99         m_ccw   = ccw;
 100         m_start = a1;
 101         m_end   = a2;
 102         m_initialized = true;
 103     }
 104
 105 }