Repo created

3party/agg/agg_ellipse.h

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+//----------------------------------------------------------------------------
+// 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
+//----------------------------------------------------------------------------
+//
+// class ellipse
+//
+//----------------------------------------------------------------------------
+
+#ifndef AGG_ELLIPSE_INCLUDED
+#define AGG_ELLIPSE_INCLUDED
+
+#include "agg_basics.h"
+#include <math.h>
+
+namespace agg
+{
+
+    //----------------------------------------------------------------ellipse
+    class ellipse
+    {
+    public:
+        ellipse() : 
+            m_x(0.0), m_y(0.0), m_rx(1.0), m_ry(1.0), m_scale(1.0), 
+            m_num(4), m_step(0), m_cw(false) {}
+
+        ellipse(double x, double y, double rx, double ry, 
+                unsigned num_steps=0, bool cw=false) :
+            m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0), 
+            m_num(num_steps), m_step(0), m_cw(cw) 
+        {
+            if(m_num == 0) calc_num_steps();
+        }
+
+        void init(double x, double y, double rx, double ry, 
+                  unsigned num_steps=0, bool cw=false);
+
+        void approximation_scale(double scale);
+        void rewind(unsigned path_id);
+        unsigned vertex(double* x, double* y);
+
+    private:
+        void calc_num_steps();
+
+        double m_x;
+        double m_y;
+        double m_rx;
+        double m_ry;
+        double m_scale;
+        unsigned m_num;
+        unsigned m_step;
+        bool m_cw;
+    };
+
+    //------------------------------------------------------------------------
+    inline void ellipse::init(double x, double y, double rx, double ry, 
+                              unsigned num_steps, bool cw)
+    {
+        m_x = x;
+        m_y = y;
+        m_rx = rx;
+        m_ry = ry;
+        m_num = num_steps;
+        m_step = 0;
+        m_cw = cw;
+        if(m_num == 0) calc_num_steps();
+    }
+
+    //------------------------------------------------------------------------
+    inline void ellipse::approximation_scale(double scale)
+    {   
+        m_scale = scale;
+        calc_num_steps();
+    }
+
+    //------------------------------------------------------------------------
+    inline void ellipse::calc_num_steps()
+    {
+        double ra = (fabs(m_rx) + fabs(m_ry)) / 2;
+        double da = acos(ra / (ra + 0.125 / m_scale)) * 2;
+        m_num = uround(2*pi / da);
+    }
+
+    //------------------------------------------------------------------------
+    inline void ellipse::rewind(unsigned)
+    {
+        m_step = 0;
+    }
+
+    //------------------------------------------------------------------------
+    inline unsigned ellipse::vertex(double* x, double* y)
+    {
+        if(m_step == m_num) 
+        {
+            ++m_step;
+            return path_cmd_end_poly | path_flags_close | path_flags_ccw;
+        }
+        if(m_step > m_num) return path_cmd_stop;
+        double angle = double(m_step) / double(m_num) * 2.0 * pi;
+        if(m_cw) angle = 2.0 * pi - angle;
+        *x = m_x + cos(angle) * m_rx;
+        *y = m_y + sin(angle) * m_ry;
+        m_step++;
+        return ((m_step == 1) ? path_cmd_move_to : path_cmd_line_to);
+    }
+
+}
+
+
+
+#endif
+
+