96 lines
3.7 KiB
C
96 lines
3.7 KiB
C
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//----------------------------------------------------------------------------
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// Anti-Grain Geometry - Version 2.2
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// Copyright (C) 2002-2004 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 gamma_spline
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//
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//----------------------------------------------------------------------------
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#ifndef AGG_GAMMA_SPLINE_INCLUDED
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#define AGG_GAMMA_SPLINE_INCLUDED
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#include "agg_basics.h"
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#include "agg_bspline.h"
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namespace agg
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{
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//------------------------------------------------------------------------
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// Class-helper for calculation gamma-correction arrays. A gamma-correction
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// array is an array of 256 unsigned chars that determine the actual values
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// of Anti-Aliasing for each pixel coverage value from 0 to 255. If all the
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// values in the array are equal to its index, i.e. 0,1,2,3,... there's
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// no gamma-correction. Class agg::polyfill allows you to use custom
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// gamma-correction arrays. You can calculate it using any approach, and
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// class gamma_spline allows you to calculate almost any reasonable shape
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// of the gamma-curve with using only 4 values - kx1, ky1, kx2, ky2.
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//
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// kx2
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// +----------------------------------+
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// | | | . |
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// | | | . | ky2
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// | | . ------|
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// | | . |
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// | | . |
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// |----------------.|----------------|
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// | . | |
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// | . | |
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// |-------. | |
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// ky1 | . | | |
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// | . | | |
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// +----------------------------------+
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// kx1
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//
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// Each value can be in range [0...2]. Value 1.0 means one quarter of the
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// bounding rectangle. Function values() calculates the curve by these
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// 4 values. After calling it one can get the gamma-array with call gamma().
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// Class also supports the vertex source interface, i.e rewind() and
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// vertex(). It's made for convinience and used in class gamma_ctrl.
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// Before calling rewind/vertex one must set the bounding box
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// box() using pixel coordinates.
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//------------------------------------------------------------------------
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class gamma_spline
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{
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public:
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gamma_spline();
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void values(double kx1, double ky1, double kx2, double ky2);
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const unsigned char* gamma() const { return m_gamma; }
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double y(double x) const;
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void values(double* kx1, double* ky1, double* kx2, double* ky2) const;
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void box(double x1, double y1, double x2, double y2);
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void rewind(unsigned);
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unsigned vertex(double* x, double* y);
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private:
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unsigned char m_gamma[256];
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double m_x[4];
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double m_y[4];
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bspline m_spline;
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double m_x1;
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double m_y1;
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double m_x2;
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double m_y2;
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double m_cur_x;
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};
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}
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#endif
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