/usr/include/agg2/ctrl/agg_gamma_spline.h is in libagg-dev 2.5+dfsg1-9.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// Anti-Grain Geometry (AGG) - Version 2.5
// A high quality rendering engine for C++
// Copyright (C) 2002-2006 Maxim Shemanarev
// Contact: mcseem@antigrain.com
// mcseemagg@yahoo.com
// http://antigrain.com
//
// AGG is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// AGG is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with AGG; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
// MA 02110-1301, USA.
//----------------------------------------------------------------------------
#ifndef AGG_GAMMA_SPLINE_INCLUDED
#define AGG_GAMMA_SPLINE_INCLUDED
#include "agg_basics.h"
#include "agg_bspline.h"
namespace agg
{
//------------------------------------------------------------------------
// Class-helper for calculation gamma-correction arrays. A gamma-correction
// array is an array of 256 unsigned chars that determine the actual values
// of Anti-Aliasing for each pixel coverage value from 0 to 255. If all the
// values in the array are equal to its index, i.e. 0,1,2,3,... there's
// no gamma-correction. Class agg::polyfill allows you to use custom
// gamma-correction arrays. You can calculate it using any approach, and
// class gamma_spline allows you to calculate almost any reasonable shape
// of the gamma-curve with using only 4 values - kx1, ky1, kx2, ky2.
//
// kx2
// +----------------------------------+
// | | | . |
// | | | . | ky2
// | | . ------|
// | | . |
// | | . |
// |----------------.|----------------|
// | . | |
// | . | |
// |-------. | |
// ky1 | . | | |
// | . | | |
// +----------------------------------+
// kx1
//
// Each value can be in range [0...2]. Value 1.0 means one quarter of the
// bounding rectangle. Function values() calculates the curve by these
// 4 values. After calling it one can get the gamma-array with call gamma().
// Class also supports the vertex source interface, i.e rewind() and
// vertex(). It's made for convinience and used in class gamma_ctrl.
// Before calling rewind/vertex one must set the bounding box
// box() using pixel coordinates.
//------------------------------------------------------------------------
class gamma_spline
{
public:
gamma_spline();
void values(double kx1, double ky1, double kx2, double ky2);
const unsigned char* gamma() const { return m_gamma; }
double y(double x) const;
void values(double* kx1, double* ky1, double* kx2, double* ky2) const;
void box(double x1, double y1, double x2, double y2);
void rewind(unsigned);
unsigned vertex(double* x, double* y);
private:
unsigned char m_gamma[256];
double m_x[4];
double m_y[4];
bspline m_spline;
double m_x1;
double m_y1;
double m_x2;
double m_y2;
double m_cur_x;
};
}
#endif
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