/usr/include/mapnik/agg/agg_gamma_functions.h is in libmapnik-dev 2.2.0+ds1-6build2.
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 - 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
//----------------------------------------------------------------------------
#ifndef AGG_GAMMA_FUNCTIONS_INCLUDED
#define AGG_GAMMA_FUNCTIONS_INCLUDED
#include <cmath>
#include "agg_basics.h"
namespace agg
{
//===============================================================gamma_none
struct gamma_none
{
double operator()(double x) const { return x; }
};
//==============================================================gamma_power
class gamma_power
{
public:
gamma_power() : m_gamma(1.0) {}
gamma_power(double g) : m_gamma(g) {}
void gamma(double g) { m_gamma = g; }
double gamma() const { return m_gamma; }
double operator() (double x) const
{
if (x == 0.0) return 0.0;
return pow(x, m_gamma);
}
private:
double m_gamma;
};
//==========================================================gamma_threshold
class gamma_threshold
{
public:
gamma_threshold() : m_threshold(0.5) {}
gamma_threshold(double t) : m_threshold(t) {}
void threshold(double t) { m_threshold = t; }
double threshold() const { return m_threshold; }
double operator() (double x) const
{
return (x < m_threshold) ? 0.0 : 1.0;
}
private:
double m_threshold;
};
//============================================================gamma_linear
class gamma_linear
{
public:
gamma_linear() : m_start(0.0), m_end(1.0) {}
gamma_linear(double s, double e) : m_start(s), m_end(e) {}
void set(double s, double e) { m_start = s; m_end = e; }
void start(double s) { m_start = s; }
void end(double e) { m_end = e; }
double start() const { return m_start; }
double end() const { return m_end; }
double operator() (double x) const
{
if(x < m_start) return 0.0;
if(x > m_end) return 1.0;
double delta = m_end - m_start;
// avoid nan from potential zero division
// https://github.com/mapnik/mapnik/issues/761
if (delta <= 0.0) return 0.0;
return (x - m_start) / delta;
}
private:
double m_start;
double m_end;
};
//==========================================================gamma_multiply
class gamma_multiply
{
public:
gamma_multiply() : m_mul(1.0) {}
gamma_multiply(double v) : m_mul(v) {}
void value(double v) { m_mul = v; }
double value() const { return m_mul; }
double operator() (double x) const
{
double y = x * m_mul;
if(y > 1.0) y = 1.0;
return y;
}
private:
double m_mul;
};
}
#endif
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