agg/source/agg_curves.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 // classes curve3 and curve4
  17 //
  18 //----------------------------------------------------------------------------
  19
  20 #include <math.h>
  21 #include "agg_curves.h"
  22
  23 namespace agg
  24 {
  25
  26     //------------------------------------------------------------------------
  27     void curve3::init(double x1, double y1,
  28                       double x2, double y2,
  29                       double x3, double y3)
  30     {
  31         m_start_x = x1;
  32         m_start_y = y1;
  33         m_end_x   = x3;
  34         m_end_y   = y3;
  35
  36         double dx1 = x2 - x1;
  37         double dy1 = y2 - y1;
  38         double dx2 = x3 - x2;
  39         double dy2 = y3 - y2;
  40
  41         double len = sqrt(dx1 * dx1 + dy1 * dy1) + sqrt(dx2 * dx2 + dy2 * dy2);
  42
  43         m_num_steps = int(len * 0.25 * m_scale);
  44
  45         if(m_num_steps < 2)
  46         {
  47             m_num_steps = 2;
  48         }
  49
  50         double subdivide_step  = 1.0 / m_num_steps;
  51         double subdivide_step2 = subdivide_step * subdivide_step;
  52
  53         double tmpx = (x1 - x2 * 2.0 + x3) * subdivide_step2;
  54         double tmpy = (y1 - y2 * 2.0 + y3) * subdivide_step2;
  55
  56         m_saved_fx = m_fx = x1;
  57         m_saved_fy = m_fy = y1;
  58
  59         m_saved_dfx = m_dfx = tmpx + (x2 - x1) * (2.0 * subdivide_step);
  60         m_saved_dfy = m_dfy = tmpy + (y2 - y1) * (2.0 * subdivide_step);
  61
  62         m_ddfx = tmpx * 2.0;
  63         m_ddfy = tmpy * 2.0;
  64
  65         m_step = m_num_steps;
  66     }
  67
  68
  69
  70
  71     //------------------------------------------------------------------------
  72     void curve3::rewind(unsigned)
  73     {
  74         if(m_num_steps == 0)
  75         {
  76             m_step = -1;
  77             return;
  78         }
  79         m_step = m_num_steps;
  80         m_fx   = m_saved_fx;
  81         m_fy   = m_saved_fy;
  82         m_dfx  = m_saved_dfx;
  83         m_dfy  = m_saved_dfy;
  84     }
  85
  86
  87
  88
  89     //------------------------------------------------------------------------
  90     unsigned curve3::vertex(double* x, double* y)
  91     {
  92         if(m_step < 0) return path_cmd_stop;
  93         if(m_step == m_num_steps)
  94         {
  95             *x = m_start_x;
  96             *y = m_start_y;
  97             --m_step;
  98             return path_cmd_move_to;
  99         }
 100         if(m_step == 0)
 101         {
 102             *x = m_end_x;
 103             *y = m_end_y;
 104             --m_step;
 105             return path_cmd_line_to;
 106         }
 107         m_fx  += m_dfx;
 108         m_fy  += m_dfy;
 109         m_dfx += m_ddfx;
 110         m_dfy += m_ddfy;
 111         *x = m_fx;
 112         *y = m_fy;
 113         --m_step;
 114         return path_cmd_line_to;
 115     }
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129     //------------------------------------------------------------------------
 130     void curve4::init(double x1, double y1,
 131                       double x2, double y2,
 132                       double x3, double y3,
 133                       double x4, double y4)
 134     {
 135         m_start_x = x1;
 136         m_start_y = y1;
 137         m_end_x   = x4;
 138         m_end_y   = y4;
 139
 140         double dx1 = x2 - x1;
 141         double dy1 = y2 - y1;
 142         double dx2 = x3 - x2;
 143         double dy2 = y3 - y2;
 144         double dx3 = x4 - x3;
 145         double dy3 = y4 - y3;
 146
 147         double len = sqrt(dx1 * dx1 + dy1 * dy1) +
 148                      sqrt(dx2 * dx2 + dy2 * dy2) +
 149                      sqrt(dx3 * dx3 + dy3 * dy3);
 150
 151         m_num_steps = int(len * 0.25 * m_scale);
 152
 153         if(m_num_steps < 2)
 154         {
 155             m_num_steps = 2;
 156         }
 157
 158         double subdivide_step  = 1.0 / m_num_steps;
 159         double subdivide_step2 = subdivide_step * subdivide_step;
 160         double subdivide_step3 = subdivide_step * subdivide_step * subdivide_step;
 161
 162         double pre1 = 3.0 * subdivide_step;
 163         double pre2 = 3.0 * subdivide_step2;
 164         double pre4 = 6.0 * subdivide_step2;
 165         double pre5 = 6.0 * subdivide_step3;
 166
 167         double tmp1x = x1 - x2 * 2.0 + x3;
 168         double tmp1y = y1 - y2 * 2.0 + y3;
 169
 170         double tmp2x = (x2 - x3) * 3.0 - x1 + x4;
 171         double tmp2y = (y2 - y3) * 3.0 - y1 + y4;
 172
 173         m_saved_fx = m_fx = x1;
 174         m_saved_fy = m_fy = y1;
 175
 176         m_saved_dfx = m_dfx = (x2 - x1) * pre1 + tmp1x * pre2 + tmp2x * subdivide_step3;
 177         m_saved_dfy = m_dfy = (y2 - y1) * pre1 + tmp1y * pre2 + tmp2y * subdivide_step3;
 178
 179         m_saved_ddfx = m_ddfx = tmp1x * pre4 + tmp2x * pre5;
 180         m_saved_ddfy = m_ddfy = tmp1y * pre4 + tmp2y * pre5;
 181
 182         m_dddfx = tmp2x * pre5;
 183         m_dddfy = tmp2y * pre5;
 184
 185         m_step = m_num_steps;
 186     }
 187
 188
 189
 190
 191     //------------------------------------------------------------------------
 192     void curve4::rewind(unsigned)
 193     {
 194         if(m_num_steps == 0)
 195         {
 196             m_step = -1;
 197             return;
 198         }
 199         m_step = m_num_steps;
 200         m_fx   = m_saved_fx;
 201         m_fy   = m_saved_fy;
 202         m_dfx  = m_saved_dfx;
 203         m_dfy  = m_saved_dfy;
 204         m_ddfx = m_saved_ddfx;
 205         m_ddfy = m_saved_ddfy;
 206     }
 207
 208
 209
 210
 211
 212     //------------------------------------------------------------------------
 213     unsigned curve4::vertex(double* x, double* y)
 214     {
 215         if(m_step < 0) return path_cmd_stop;
 216         if(m_step == m_num_steps)
 217         {
 218             *x = m_start_x;
 219             *y = m_start_y;
 220             --m_step;
 221             return path_cmd_move_to;
 222         }
 223         if(m_step == 0)
 224         {
 225             *x = m_end_x;
 226             *y = m_end_y;
 227             --m_step;
 228             return path_cmd_line_to;
 229         }
 230         m_fx   += m_dfx;
 231         m_fy   += m_dfy;
 232         m_dfx  += m_ddfx;
 233         m_dfy  += m_ddfy;
 234         m_ddfx += m_dddfx;
 235         m_ddfy += m_dddfy;
 236         *x = m_fx;
 237         *y = m_fy;
 238         --m_step;
 239         return path_cmd_line_to;
 240     }
 241
 242
 243
 244
 245 }
 246