text: //----------------------------------------------------------------------------
  // Anti-Grain Geometry - Version 2.4
  // Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
  //
  // Permission to copy, use, modify, sell and distribute this software 
  // is granted provided this copyright notice appears in all copies. 
  // This software is provided "as is" without express or implied
  // warranty, and with no claim as to its suitability for any purpose.
  //
  //----------------------------------------------------------------------------
  // Contact: mcseem@antigrain.com
  //          mcseemagg@yahoo.com
  //          http://www.antigrain.com
  //----------------------------------------------------------------------------
  #ifndef AGG_LINE_AA_BASICS_INCLUDED
  #define AGG_LINE_AA_BASICS_INCLUDED
  
  #include <stdlib.h>
  #include "agg_basics.h"
  
  namespace agg
  {
  
      // See Implementation agg_line_aa_basics.cpp 
  
      //-------------------------------------------------------------------------
      enum line_subpixel_scale_e
      {
          line_subpixel_shift = 8,                          //----line_subpixel_shift
          line_subpixel_scale  = 1 << line_subpixel_shift,  //----line_subpixel_scale
          line_subpixel_mask  = line_subpixel_scale - 1,    //----line_subpixel_mask
          line_max_coord      = (1 << 28) - 1,              //----line_max_coord
          line_max_length = 1 << (line_subpixel_shift + 10) //----line_max_length
      };
  
      //-------------------------------------------------------------------------
      enum line_mr_subpixel_scale_e
      {
          line_mr_subpixel_shift = 4,                           //----line_mr_subpixel_shift
          line_mr_subpixel_scale = 1 << line_mr_subpixel_shift, //----line_mr_subpixel_scale 
          line_mr_subpixel_mask  = line_mr_subpixel_scale - 1   //----line_mr_subpixel_mask 
      };
  
      //------------------------------------------------------------------line_mr
      AGG_INLINE int line_mr(int x) 
      { 
          return x >> (line_subpixel_shift - line_mr_subpixel_shift); 
      }
  
      //-------------------------------------------------------------------line_hr
      AGG_INLINE int line_hr(int x) 
      { 
          return x << (line_subpixel_shift - line_mr_subpixel_shift); 
      }
  
      //---------------------------------------------------------------line_dbl_hr
      AGG_INLINE int line_dbl_hr(int x) 
      { 
          return x << line_subpixel_shift;
      }
  
      //---------------------------------------------------------------line_coord
      struct line_coord
      {
          AGG_INLINE static int conv(real x)
          {
              return iround(x * line_subpixel_scale);
          }
      };
  
      //-----------------------------------------------------------line_coord_sat
      struct line_coord_sat
      {
          AGG_INLINE static int conv(real x)
          {
              return saturation<line_max_coord>::iround(x * line_subpixel_scale);
          }
      };
  
      //==========================================================line_parameters
      struct line_parameters
      {
          //---------------------------------------------------------------------
          line_parameters() {}
          line_parameters(int x1_, int y1_, int x2_, int y2_, int len_) :
              x1(x1_), y1(y1_), x2(x2_), y2(y2_), 
              dx(abs(x2_ - x1_)),
              dy(abs(y2_ - y1_)),
              sx((x2_ > x1_) ? 1 : -1),
              sy((y2_ > y1_) ? 1 : -1),
              vertical(dy >= dx),
              inc(vertical ? sy : sx),
              len(len_),
              octant((sy & 4) | (sx & 2) | int(vertical))
          {
          }
  
          //---------------------------------------------------------------------
          unsigned orthogonal_quadrant() const { return s_orthogonal_quadrant[octant]; }
          unsigned diagonal_quadrant()   const { return s_diagonal_quadrant[octant];   }
  
          //---------------------------------------------------------------------
          bool same_orthogonal_quadrant(const line_parameters& lp) const
          {
              return s_orthogonal_quadrant[octant] == s_orthogonal_quadrant[lp.octant];
          }
  
          //---------------------------------------------------------------------
          bool same_diagonal_quadrant(const line_parameters& lp) const
          {
              return s_diagonal_quadrant[octant] == s_diagonal_quadrant[lp.octant];
          }
  
          //---------------------------------------------------------------------
          void divide(line_parameters& lp1, line_parameters& lp2) const
          {
              int xmid = (x1 + x2) >> 1;
              int ymid = (y1 + y2) >> 1;
              int len2 = len >> 1;
  
              lp1 = *this;
              lp2 = *this;
  
              lp1.x2  = xmid;
              lp1.y2  = ymid;
              lp1.len = len2;
              lp1.dx  = abs(lp1.x2 - lp1.x1);
              lp1.dy  = abs(lp1.y2 - lp1.y1);
  
              lp2.x1  = xmid;
              lp2.y1  = ymid;
              lp2.len = len2;
              lp2.dx  = abs(lp2.x2 - lp2.x1);
              lp2.dy  = abs(lp2.y2 - lp2.y1);
          }
          
          //---------------------------------------------------------------------
          int x1, y1, x2, y2, dx, dy, sx, sy;
          bool vertical;
          int inc;
          int len;
          int octant;
  
          //---------------------------------------------------------------------
          static const int8u s_orthogonal_quadrant[8];
          static const int8u s_diagonal_quadrant[8];
      };
  
  
  
      // See Implementation agg_line_aa_basics.cpp 
  
      //----------------------------------------------------------------bisectrix
      void bisectrix(const line_parameters& l1, 
                     const line_parameters& l2, 
                     int* x, int* y);
  
  
      //-------------------------------------------fix_degenerate_bisectrix_start
      void inline fix_degenerate_bisectrix_start(const line_parameters& lp, 
                                                 int* x, int* y)
      {
          int d = iround((real(*x - lp.x2) * real(lp.y2 - lp.y1) - 
                          real(*y - lp.y2) * real(lp.x2 - lp.x1)) / lp.len);
          if(d < line_subpixel_scale/2)
          {
              *x = lp.x1 + (lp.y2 - lp.y1);
              *y = lp.y1 - (lp.x2 - lp.x1);
          }
      }
  
  
      //---------------------------------------------fix_degenerate_bisectrix_end
      void inline fix_degenerate_bisectrix_end(const line_parameters& lp, 
                                               int* x, int* y)
      {
          int d = iround((real(*x - lp.x2) * real(lp.y2 - lp.y1) - 
                          real(*y - lp.y2) * real(lp.x2 - lp.x1)) / lp.len);
          if(d < line_subpixel_scale/2)
          {
              *x = lp.x2 + (lp.y2 - lp.y1);
              *y = lp.y2 - (lp.x2 - lp.x1);
          }
      }
  
  
  }
  
  #endif
  