124 lines
3.6 KiB
C++
124 lines
3.6 KiB
C++
//----------------------------------------------------------------------------
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// Anti-Grain Geometry - Version 2.4
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// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
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//
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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//
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//----------------------------------------------------------------------------
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// Contact: mcseem@antigrain.com
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// mcseemagg@yahoo.com
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// http://www.antigrain.com
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//----------------------------------------------------------------------------
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//
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// class ellipse
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//
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//----------------------------------------------------------------------------
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#ifndef AGG_ELLIPSE_INCLUDED
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#define AGG_ELLIPSE_INCLUDED
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#include "agg_basics.h"
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#include <cmath>
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namespace agg
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{
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//----------------------------------------------------------------ellipse
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class ellipse
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{
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public:
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ellipse() :
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m_x(0.0), m_y(0.0), m_rx(1.0), m_ry(1.0), m_scale(1.0),
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m_num(4), m_step(0), m_cw(false) {}
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ellipse(double x, double y, double rx, double ry,
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unsigned num_steps=0, bool cw=false) :
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m_x(x), m_y(y), m_rx(rx), m_ry(ry), m_scale(1.0),
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m_num(num_steps), m_step(0), m_cw(cw)
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{
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if(m_num == 0) calc_num_steps();
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}
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void init(double x, double y, double rx, double ry,
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unsigned num_steps=0, bool cw=false);
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void approximation_scale(double scale);
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void rewind(unsigned path_id);
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unsigned vertex(double* x, double* y);
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private:
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void calc_num_steps();
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double m_x;
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double m_y;
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double m_rx;
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double m_ry;
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double m_scale;
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unsigned m_num;
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unsigned m_step;
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bool m_cw;
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};
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//------------------------------------------------------------------------
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inline void ellipse::init(double x, double y, double rx, double ry,
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unsigned num_steps, bool cw)
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{
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m_x = x;
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m_y = y;
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m_rx = rx;
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m_ry = ry;
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m_num = num_steps;
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m_step = 0;
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m_cw = cw;
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if(m_num == 0) calc_num_steps();
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}
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//------------------------------------------------------------------------
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inline void ellipse::approximation_scale(double scale)
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{
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m_scale = scale;
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calc_num_steps();
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}
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//------------------------------------------------------------------------
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inline void ellipse::calc_num_steps()
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{
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double ra = (std::fabs(m_rx) + std::fabs(m_ry)) / 2;
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double da = std::acos(ra / (ra + 0.125 / m_scale)) * 2;
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m_num = uround(2*pi / da);
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}
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//------------------------------------------------------------------------
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inline void ellipse::rewind(unsigned)
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{
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m_step = 0;
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}
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//------------------------------------------------------------------------
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inline unsigned ellipse::vertex(double* x, double* y)
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{
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if(m_step == m_num)
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{
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++m_step;
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return path_cmd_end_poly | path_flags_close | path_flags_ccw;
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}
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if(m_step > m_num) return path_cmd_stop;
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double angle = double(m_step) / double(m_num) * 2.0 * pi;
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if(m_cw) angle = 2.0 * pi - angle;
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*x = m_x + std::cos(angle) * m_rx;
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*y = m_y + std::sin(angle) * m_ry;
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m_step++;
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return ((m_step == 1) ? path_cmd_move_to : path_cmd_line_to);
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}
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}
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#endif
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