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
  //----------------------------------------------------------------------------
  //
  // Horizontal span interpolator for use with an arbitrary transformer
  // The efficiency highly depends on the operations done in the transformer
  //
  //----------------------------------------------------------------------------
  
  #ifndef AGG_SPAN_INTERPOLATOR_TRANS_INCLUDED
  #define AGG_SPAN_INTERPOLATOR_TRANS_INCLUDED
  
  #include "agg_basics.h"
  
  namespace agg
  {
      //=================================================span_interpolator_trans
      template<class Transformer, unsigned SubpixelShift = 8>
      class span_interpolator_trans
      {
      public:
          typedef Transformer trans_type;
          enum subpixel_scale_e
          {
              subpixel_shift = SubpixelShift,
              subpixel_scale = 1 << subpixel_shift
          };
  
          //--------------------------------------------------------------------
          span_interpolator_trans() {}
          span_interpolator_trans(const trans_type& trans) : m_trans(&trans) {}
          span_interpolator_trans(const trans_type& trans,
                                  double x, double y, unsigned) :
              m_trans(&trans)
          {
              begin(x, y, 0);
          }
  
          //----------------------------------------------------------------
          const trans_type& transformer() const { return *m_trans; }
          void transformer(const trans_type& trans) { m_trans = &trans; }
  
          //----------------------------------------------------------------
          void begin(double x, double y, unsigned)
          {
              m_x = x;
              m_y = y;
              m_trans->transform(&x, &y);
              m_ix = iround(x * subpixel_scale);
              m_iy = iround(y * subpixel_scale);
          }
  
          //----------------------------------------------------------------
          void operator++()
          {
              m_x += 1.0;
              double x = m_x;
              double y = m_y;
              m_trans->transform(&x, &y);
              m_ix = iround(x * subpixel_scale);
              m_iy = iround(y * subpixel_scale);
          }
  
          //----------------------------------------------------------------
          void coordinates(int* x, int* y) const
          {
              *x = m_ix;
              *y = m_iy;
          }
  
      private:
          const trans_type* m_trans;
          double            m_x;
          double            m_y;
          int               m_ix;
          int               m_iy;
      };
  
  }
  
  #endif
  