/usr/include/mapnik/agg/agg_image_filters.h is in libmapnik-dev 2.2.0+ds1-7+b2.
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
//----------------------------------------------------------------------------
//
// Image transformation filters,
// Filtering classes (image_filter_lut, image_filter),
// Basic filter shape classes
//----------------------------------------------------------------------------
#ifndef AGG_IMAGE_FILTERS_INCLUDED
#define AGG_IMAGE_FILTERS_INCLUDED
#include "agg_array.h"
#include "agg_math.h"
namespace agg
{
// See Implementation agg_image_filters.cpp
enum image_filter_scale_e
{
image_filter_shift = 14, //----image_filter_shift
image_filter_scale = 1 << image_filter_shift, //----image_filter_scale
image_filter_mask = image_filter_scale - 1 //----image_filter_mask
};
enum image_subpixel_scale_e
{
image_subpixel_shift = 8, //----image_subpixel_shift
image_subpixel_scale = 1 << image_subpixel_shift, //----image_subpixel_scale
image_subpixel_mask = image_subpixel_scale - 1 //----image_subpixel_mask
};
//-----------------------------------------------------image_filter_lut
class image_filter_lut
{
public:
template<class FilterF> void calculate(const FilterF& filter,
bool normalization=true)
{
double r = filter.radius();
realloc_lut(r);
unsigned i;
unsigned pivot = diameter() << (image_subpixel_shift - 1);
for(i = 0; i < pivot; i++)
{
double x = double(i) / double(image_subpixel_scale);
double y = filter.calc_weight(x);
m_weight_array[pivot + i] =
m_weight_array[pivot - i] = (int16)iround(y * image_filter_scale);
}
unsigned end = (diameter() << image_subpixel_shift) - 1;
m_weight_array[0] = m_weight_array[end];
if(normalization)
{
normalize();
}
}
image_filter_lut() : m_radius(0), m_diameter(0), m_start(0) {}
template<class FilterF> image_filter_lut(const FilterF& filter,
bool normalization=true)
{
calculate(filter, normalization);
}
double radius() const { return m_radius; }
unsigned diameter() const { return m_diameter; }
int start() const { return m_start; }
const int16* weight_array() const { return &m_weight_array[0]; }
void normalize();
private:
void realloc_lut(double radius);
image_filter_lut(const image_filter_lut&);
const image_filter_lut& operator = (const image_filter_lut&);
double m_radius;
unsigned m_diameter;
int m_start;
pod_array<int16> m_weight_array;
};
//--------------------------------------------------------image_filter
template<class FilterF> class image_filter : public image_filter_lut
{
public:
image_filter()
{
calculate(m_filter_function);
}
private:
FilterF m_filter_function;
};
//-----------------------------------------------image_filter_bilinear
struct image_filter_bilinear
{
static double radius() { return 1.0; }
static double calc_weight(double x)
{
return 1.0 - x;
}
};
//-----------------------------------------------image_filter_hanning
struct image_filter_hanning
{
static double radius() { return 1.0; }
static double calc_weight(double x)
{
return 0.5 + 0.5 * cos(pi * x);
}
};
//-----------------------------------------------image_filter_hamming
struct image_filter_hamming
{
static double radius() { return 1.0; }
static double calc_weight(double x)
{
return 0.54 + 0.46 * cos(pi * x);
}
};
//-----------------------------------------------image_filter_hermite
struct image_filter_hermite
{
static double radius() { return 1.0; }
static double calc_weight(double x)
{
return (2.0 * x - 3.0) * x * x + 1.0;
}
};
//------------------------------------------------image_filter_quadric
struct image_filter_quadric
{
static double radius() { return 1.5; }
static double calc_weight(double x)
{
double t;
if(x < 0.5) return 0.75 - x * x;
if(x < 1.5) {t = x - 1.5; return 0.5 * t * t;}
return 0.0;
}
};
//------------------------------------------------image_filter_bicubic
class image_filter_bicubic
{
static double pow3(double x)
{
return (x <= 0.0) ? 0.0 : x * x * x;
}
public:
static double radius() { return 2.0; }
static double calc_weight(double x)
{
return
(1.0/6.0) *
(pow3(x + 2) - 4 * pow3(x + 1) + 6 * pow3(x) - 4 * pow3(x - 1));
}
};
//-------------------------------------------------image_filter_kaiser
class image_filter_kaiser
{
double a;
double i0a;
double epsilon;
public:
image_filter_kaiser(double b = 6.33) :
a(b), epsilon(1e-12)
{
i0a = 1.0 / bessel_i0(b);
}
static double radius() { return 1.0; }
double calc_weight(double x) const
{
return bessel_i0(a * sqrt(1. - x * x)) * i0a;
}
private:
double bessel_i0(double x) const
{
int i;
double sum, y, t;
sum = 1.;
y = x * x / 4.;
t = y;
for(i = 2; t > epsilon; i++)
{
sum += t;
t *= (double)y / (i * i);
}
return sum;
}
};
//----------------------------------------------image_filter_catrom
struct image_filter_catrom
{
static double radius() { return 2.0; }
static double calc_weight(double x)
{
if(x < 1.0) return 0.5 * (2.0 + x * x * (-5.0 + x * 3.0));
if(x < 2.0) return 0.5 * (4.0 + x * (-8.0 + x * (5.0 - x)));
return 0.;
}
};
//---------------------------------------------image_filter_mitchell
class image_filter_mitchell
{
double p0, p2, p3;
double q0, q1, q2, q3;
public:
image_filter_mitchell(double b = 1.0/3.0, double c = 1.0/3.0) :
p0((6.0 - 2.0 * b) / 6.0),
p2((-18.0 + 12.0 * b + 6.0 * c) / 6.0),
p3((12.0 - 9.0 * b - 6.0 * c) / 6.0),
q0((8.0 * b + 24.0 * c) / 6.0),
q1((-12.0 * b - 48.0 * c) / 6.0),
q2((6.0 * b + 30.0 * c) / 6.0),
q3((-b - 6.0 * c) / 6.0)
{}
static double radius() { return 2.0; }
double calc_weight(double x) const
{
if(x < 1.0) return p0 + x * x * (p2 + x * p3);
if(x < 2.0) return q0 + x * (q1 + x * (q2 + x * q3));
return 0.0;
}
};
//----------------------------------------------image_filter_spline16
struct image_filter_spline16
{
static double radius() { return 2.0; }
static double calc_weight(double x)
{
if(x < 1.0)
{
return ((x - 9.0/5.0 ) * x - 1.0/5.0 ) * x + 1.0;
}
return ((-1.0/3.0 * (x-1) + 4.0/5.0) * (x-1) - 7.0/15.0 ) * (x-1);
}
};
//---------------------------------------------image_filter_spline36
struct image_filter_spline36
{
static double radius() { return 3.0; }
static double calc_weight(double x)
{
if(x < 1.0)
{
return ((13.0/11.0 * x - 453.0/209.0) * x - 3.0/209.0) * x + 1.0;
}
if(x < 2.0)
{
return ((-6.0/11.0 * (x-1) + 270.0/209.0) * (x-1) - 156.0/ 209.0) * (x-1);
}
return ((1.0/11.0 * (x-2) - 45.0/209.0) * (x-2) + 26.0/209.0) * (x-2);
}
};
//----------------------------------------------image_filter_gaussian
struct image_filter_gaussian
{
static double radius() { return 2.0; }
static double calc_weight(double x)
{
return exp(-2.0 * x * x) * sqrt(2.0 / pi);
}
};
//------------------------------------------------image_filter_bessel
struct image_filter_bessel
{
static double radius() { return 3.2383; }
static double calc_weight(double x)
{
return (x == 0.0) ? pi / 4.0 : besj(pi * x, 1) / (2.0 * x);
}
};
//-------------------------------------------------image_filter_sinc
class image_filter_sinc
{
public:
image_filter_sinc(double r) : m_radius(r < 2.0 ? 2.0 : r) {}
double radius() const { return m_radius; }
double calc_weight(double x) const
{
if(x == 0.0) return 1.0;
x *= pi;
return sin(x) / x;
}
private:
double m_radius;
};
//-----------------------------------------------image_filter_lanczos
class image_filter_lanczos
{
public:
image_filter_lanczos(double r) : m_radius(r < 2.0 ? 2.0 : r) {}
double radius() const { return m_radius; }
double calc_weight(double x) const
{
if(x == 0.0) return 1.0;
if(x > m_radius) return 0.0;
x *= pi;
double xr = x / m_radius;
return (sin(x) / x) * (sin(xr) / xr);
}
private:
double m_radius;
};
//----------------------------------------------image_filter_blackman
class image_filter_blackman
{
public:
image_filter_blackman(double r) : m_radius(r < 2.0 ? 2.0 : r) {}
double radius() const { return m_radius; }
double calc_weight(double x) const
{
if(x == 0.0) return 1.0;
if(x > m_radius) return 0.0;
x *= pi;
double xr = x / m_radius;
return (sin(x) / x) * (0.42 + 0.5*cos(xr) + 0.08*cos(2*xr));
}
private:
double m_radius;
};
//------------------------------------------------image_filter_sinc36
class image_filter_sinc36 : public image_filter_sinc
{ public: image_filter_sinc36() : image_filter_sinc(3.0){} };
//------------------------------------------------image_filter_sinc64
class image_filter_sinc64 : public image_filter_sinc
{ public: image_filter_sinc64() : image_filter_sinc(4.0){} };
//-----------------------------------------------image_filter_sinc100
class image_filter_sinc100 : public image_filter_sinc
{ public: image_filter_sinc100() : image_filter_sinc(5.0){} };
//-----------------------------------------------image_filter_sinc144
class image_filter_sinc144 : public image_filter_sinc
{ public: image_filter_sinc144() : image_filter_sinc(6.0){} };
//-----------------------------------------------image_filter_sinc196
class image_filter_sinc196 : public image_filter_sinc
{ public: image_filter_sinc196() : image_filter_sinc(7.0){} };
//-----------------------------------------------image_filter_sinc256
class image_filter_sinc256 : public image_filter_sinc
{ public: image_filter_sinc256() : image_filter_sinc(8.0){} };
//---------------------------------------------image_filter_lanczos36
class image_filter_lanczos36 : public image_filter_lanczos
{ public: image_filter_lanczos36() : image_filter_lanczos(3.0){} };
//---------------------------------------------image_filter_lanczos64
class image_filter_lanczos64 : public image_filter_lanczos
{ public: image_filter_lanczos64() : image_filter_lanczos(4.0){} };
//--------------------------------------------image_filter_lanczos100
class image_filter_lanczos100 : public image_filter_lanczos
{ public: image_filter_lanczos100() : image_filter_lanczos(5.0){} };
//--------------------------------------------image_filter_lanczos144
class image_filter_lanczos144 : public image_filter_lanczos
{ public: image_filter_lanczos144() : image_filter_lanczos(6.0){} };
//--------------------------------------------image_filter_lanczos196
class image_filter_lanczos196 : public image_filter_lanczos
{ public: image_filter_lanczos196() : image_filter_lanczos(7.0){} };
//--------------------------------------------image_filter_lanczos256
class image_filter_lanczos256 : public image_filter_lanczos
{ public: image_filter_lanczos256() : image_filter_lanczos(8.0){} };
//--------------------------------------------image_filter_blackman36
class image_filter_blackman36 : public image_filter_blackman
{ public: image_filter_blackman36() : image_filter_blackman(3.0){} };
//--------------------------------------------image_filter_blackman64
class image_filter_blackman64 : public image_filter_blackman
{ public: image_filter_blackman64() : image_filter_blackman(4.0){} };
//-------------------------------------------image_filter_blackman100
class image_filter_blackman100 : public image_filter_blackman
{ public: image_filter_blackman100() : image_filter_blackman(5.0){} };
//-------------------------------------------image_filter_blackman144
class image_filter_blackman144 : public image_filter_blackman
{ public: image_filter_blackman144() : image_filter_blackman(6.0){} };
//-------------------------------------------image_filter_blackman196
class image_filter_blackman196 : public image_filter_blackman
{ public: image_filter_blackman196() : image_filter_blackman(7.0){} };
//-------------------------------------------image_filter_blackman256
class image_filter_blackman256 : public image_filter_blackman
{ public: image_filter_blackman256() : image_filter_blackman(8.0){} };
}
#endif
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