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+//----------------------------------------------------------------------------
+// Anti-Grain Geometry - Version 2.3
+// 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_SPAN_GOURAUD_INCLUDED
+#define AGG_SPAN_GOURAUD_INCLUDED
+
+#include "agg_basics.h"
+#include "agg_math.h"
+#include "agg_span_generator.h"
+
+namespace agg
+{
+
+ //============================================================span_gouraud
+ template<class ColorT, class Allocator>
+ class span_gouraud : public span_generator<ColorT, Allocator>
+ {
+ public:
+ typedef ColorT color_type;
+ typedef Allocator alloc_type;
+
+ struct coord_type
+ {
+ double x;
+ double y;
+ color_type color;
+ };
+
+ //--------------------------------------------------------------------
+ span_gouraud(alloc_type& alloc) :
+ span_generator<color_type, alloc_type>(alloc),
+ m_vertex(0)
+ {
+ m_cmd[0] = path_cmd_stop;
+ }
+
+ //--------------------------------------------------------------------
+ span_gouraud(alloc_type& alloc,
+ const color_type& c1,
+ const color_type& c2,
+ const color_type& c3,
+ double x1, double y1,
+ double x2, double y2,
+ double x3, double y3,
+ double d) :
+ span_generator<color_type, alloc_type>(alloc)
+ {
+ colors(c1, c2, c3);
+ triangle(x1, y1, x2, y2, x3, y3, d);
+ }
+
+ //--------------------------------------------------------------------
+ void colors(ColorT c1, ColorT c2, ColorT c3)
+ {
+ m_coord[0].color = c1;
+ m_coord[1].color = c2;
+ m_coord[2].color = c3;
+ }
+
+ //--------------------------------------------------------------------
+ // Sets the triangle and dilates it if needed.
+ // The trick here is to calculate beveled joins in the vertices of the
+ // triangle and render it as a 6-vertex polygon.
+ // It's necessary to achieve numerical stability.
+ // However, the coordinates to interpolate colors are calculated
+ // as miter joins (calc_intersection).
+ void triangle(double x1, double y1,
+ double x2, double y2,
+ double x3, double y3,
+ double d)
+ {
+ m_coord[0].x = m_x[0] = x1;
+ m_coord[0].y = m_y[0] = y1;
+ m_coord[1].x = m_x[1] = x2;
+ m_coord[1].y = m_y[1] = y2;
+ m_coord[2].x = m_x[2] = x3;
+ m_coord[2].y = m_y[2] = y3;
+ m_cmd[0] = path_cmd_move_to;
+ m_cmd[1] = path_cmd_line_to;
+ m_cmd[2] = path_cmd_line_to;
+ m_cmd[3] = path_cmd_stop;
+
+ if(d != 0.0)
+ {
+ dilate_triangle(m_coord[0].x, m_coord[0].y,
+ m_coord[1].x, m_coord[1].y,
+ m_coord[2].x, m_coord[2].y,
+ m_x, m_y, d);
+
+ calc_intersection(m_x[4], m_y[4], m_x[5], m_y[5],
+ m_x[0], m_y[0], m_x[1], m_y[1],
+ &m_coord[0].x, &m_coord[0].y);
+
+ calc_intersection(m_x[0], m_y[0], m_x[1], m_y[1],
+ m_x[2], m_y[2], m_x[3], m_y[3],
+ &m_coord[1].x, &m_coord[1].y);
+
+ calc_intersection(m_x[2], m_y[2], m_x[3], m_y[3],
+ m_x[4], m_y[4], m_x[5], m_y[5],
+ &m_coord[2].x, &m_coord[2].y);
+ m_cmd[3] = path_cmd_line_to;
+ m_cmd[4] = path_cmd_line_to;
+ m_cmd[5] = path_cmd_line_to;
+ m_cmd[6] = path_cmd_stop;
+ }
+ }
+
+ //--------------------------------------------------------------------
+ // Vertex Source Interface to feed the coordinates to the rasterizer
+ void rewind(unsigned)
+ {
+ m_vertex = 0;
+ }
+
+ //--------------------------------------------------------------------
+ unsigned vertex(double* x, double* y)
+ {
+ *x = m_x[m_vertex];
+ *y = m_y[m_vertex];
+ return m_cmd[m_vertex++];
+ }
+
+
+
+ protected:
+ //--------------------------------------------------------------------
+ void arrange_vertices(coord_type* coord) const
+ {
+ coord[0] = m_coord[0];
+ coord[1] = m_coord[1];
+ coord[2] = m_coord[2];
+
+ if(m_coord[0].y > m_coord[2].y)
+ {
+ coord[0] = m_coord[2];
+ coord[2] = m_coord[0];
+ }
+
+ coord_type tmp;
+ if(coord[0].y > coord[1].y)
+ {
+ tmp = coord[1];
+ coord[1] = coord[0];
+ coord[0] = tmp;
+ }
+
+ if(coord[1].y > coord[2].y)
+ {
+ tmp = coord[2];
+ coord[2] = coord[1];
+ coord[1] = tmp;
+ }
+ }
+
+
+ private:
+ //--------------------------------------------------------------------
+ coord_type m_coord[3];
+ double m_x[8];
+ double m_y[8];
+ unsigned m_cmd[8];
+ unsigned m_vertex;
+ };
+
+}
+
+#endif
+