agg/source/agg_line_aa_basics.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 #include <math.h>
  17 #include "agg_line_aa_basics.h"
  18
  19 namespace agg
  20 {
  21     //-------------------------------------------------------------------------
  22     // The number of the octant is determined as a 3-bit value as follows:
  23     // bit 0 = vertical flag
  24     // bit 1 = sx < 0
  25     // bit 2 = sy < 0
  26     //
  27     // [N] shows the number of the orthogonal quadrant
  28     // <M> shows the number of the diagonal quadrant
  29     //               <1>
  30     //   [1]          |          [0]
  31     //       . (3)011 | 001(1) .
  32     //         .      |      .
  33     //           .    |    .
  34     //             .  |  .
  35     //    (2)010     .|.     000(0)
  36     // <2> ----------.+.----------- <0>
  37     //    (6)110   .  |  .   100(4)
  38     //           .    |    .
  39     //         .      |      .
  40     //       .        |        .
  41     //         (7)111 | 101(5)
  42     //   [2]          |          [3]
  43     //               <3>
  44     //                                                  0,1,2,3,4,5,6,7
  45     int8u line_parameters::s_orthogonal_quadrant[8] = { 0,0,1,1,3,3,2,2 };
  46     int8u line_parameters::s_diagonal_quadrant[8]   = { 0,1,2,1,0,3,2,3 };
  47
  48
  49
  50     //-------------------------------------------------------------------------
  51     void bisectrix(const line_parameters& l1,
  52                    const line_parameters& l2,
  53                    int* x, int* y)
  54     {
  55         double k = double(l2.len) / double(l1.len);
  56         double tx = l2.x2 - (l2.x1 - l1.x1) * k;
  57         double ty = l2.y2 - (l2.y1 - l1.y1) * k;
  58
  59         //All bisectrices must be on the right of the line
  60         //If the next point is on the left (l1 => l2.2)
  61         //then the bisectix should be rotated by 180 degrees.
  62         if(double(l2.x2 - l2.x1) * double(l2.y1 - l1.y1) <
  63            double(l2.y2 - l2.y1) * double(l2.x1 - l1.x1) + 100.0)
  64         {
  65             tx -= (tx - l2.x1) * 2.0;
  66             ty -= (ty - l2.y1) * 2.0;
  67         }
  68
  69         // Check if the bisectrix is too short
  70         double dx = tx - l2.x1;
  71         double dy = ty - l2.y1;
  72         if((int)sqrt(dx * dx + dy * dy) < line_subpixel_size)
  73         {
  74             *x = (l2.x1 + l2.x1 + (l2.y1 - l1.y1) + (l2.y2 - l2.y1)) >> 1;
  75             *y = (l2.y1 + l2.y1 - (l2.x1 - l1.x1) - (l2.x2 - l2.x1)) >> 1;
  76             return;
  77         }
  78         *x = int(tx);
  79         *y = int(ty);
  80     }
  81
  82 }