/usr/include/agg2/agg_gradient_lut.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_GRADIENT_LUT_INCLUDED
#define AGG_GRADIENT_LUT_INCLUDED
#include "agg_array.h"
#include "agg_dda_line.h"
#include "agg_color_rgba.h"
#include "agg_color_gray.h"
namespace agg
{
//======================================================color_interpolator
template<class ColorT> struct color_interpolator
{
public:
typedef ColorT color_type;
color_interpolator(const color_type& c1,
const color_type& c2,
unsigned len) :
m_c1(c1),
m_c2(c2),
m_len(len),
m_count(0)
{}
void operator ++ ()
{
++m_count;
}
color_type color() const
{
return m_c1.gradient(m_c2, double(m_count) / m_len);
}
private:
color_type m_c1;
color_type m_c2;
unsigned m_len;
unsigned m_count;
};
//========================================================================
// Fast specialization for rgba8
template<> struct color_interpolator<rgba8>
{
public:
typedef rgba8 color_type;
color_interpolator(const color_type& c1,
const color_type& c2,
unsigned len) :
r(c1.r, c2.r, len),
g(c1.g, c2.g, len),
b(c1.b, c2.b, len),
a(c1.a, c2.a, len)
{}
void operator ++ ()
{
++r; ++g; ++b; ++a;
}
color_type color() const
{
return color_type(r.y(), g.y(), b.y(), a.y());
}
private:
agg::dda_line_interpolator<14> r, g, b, a;
};
//========================================================================
// Fast specialization for gray8
template<> struct color_interpolator<gray8>
{
public:
typedef gray8 color_type;
color_interpolator(const color_type& c1,
const color_type& c2,
unsigned len) :
v(c1.v, c2.v, len),
a(c1.a, c2.a, len)
{}
void operator ++ ()
{
++v; ++a;
}
color_type color() const
{
return color_type(v.y(), a.y());
}
private:
agg::dda_line_interpolator<14> v,a;
};
//============================================================gradient_lut
template<class ColorInterpolator,
unsigned ColorLutSize=256> class gradient_lut
{
public:
typedef ColorInterpolator interpolator_type;
typedef typename interpolator_type::color_type color_type;
enum { color_lut_size = ColorLutSize };
//--------------------------------------------------------------------
gradient_lut() : m_color_lut(color_lut_size) {}
// Build Gradient Lut
// First, call remove_all(), then add_color() at least twice,
// then build_lut(). Argument "offset" in add_color must be
// in range [0...1] and defines a color stop as it is described
// in SVG specification, section Gradients and Patterns.
// The simplest linear gradient is:
// gradient_lut.add_color(0.0, start_color);
// gradient_lut.add_color(1.0, end_color);
//--------------------------------------------------------------------
void remove_all();
void add_color(double offset, const color_type& color);
void build_lut();
// Size-index Interface. This class can be used directly as the
// ColorF in span_gradient. All it needs is two access methods
// size() and operator [].
//--------------------------------------------------------------------
static unsigned size()
{
return color_lut_size;
}
const color_type& operator [] (unsigned i) const
{
return m_color_lut[i];
}
private:
//--------------------------------------------------------------------
struct color_point
{
double offset;
color_type color;
color_point() {}
color_point(double off, const color_type& c) :
offset(off), color(c)
{
if(offset < 0.0) offset = 0.0;
if(offset > 1.0) offset = 1.0;
}
};
typedef agg::pod_bvector<color_point, 4> color_profile_type;
typedef agg::pod_array<color_type> color_lut_type;
static bool offset_less(const color_point& a, const color_point& b)
{
return a.offset < b.offset;
}
static bool offset_equal(const color_point& a, const color_point& b)
{
return a.offset == b.offset;
}
//--------------------------------------------------------------------
color_profile_type m_color_profile;
color_lut_type m_color_lut;
};
//------------------------------------------------------------------------
template<class T, unsigned S>
void gradient_lut<T,S>::remove_all()
{
m_color_profile.remove_all();
}
//------------------------------------------------------------------------
template<class T, unsigned S>
void gradient_lut<T,S>::add_color(double offset, const color_type& color)
{
m_color_profile.add(color_point(offset, color));
}
//------------------------------------------------------------------------
template<class T, unsigned S>
void gradient_lut<T,S>::build_lut()
{
quick_sort(m_color_profile, offset_less);
m_color_profile.cut_at(remove_duplicates(m_color_profile, offset_equal));
if(m_color_profile.size() >= 2)
{
unsigned i;
unsigned start = uround(m_color_profile[0].offset * color_lut_size);
unsigned end;
color_type c = m_color_profile[0].color;
for(i = 0; i < start; i++)
{
m_color_lut[i] = c;
}
for(i = 1; i < m_color_profile.size(); i++)
{
end = uround(m_color_profile[i].offset * color_lut_size);
interpolator_type ci(m_color_profile[i-1].color,
m_color_profile[i ].color,
end - start + 1);
while(start < end)
{
m_color_lut[start] = ci.color();
++ci;
++start;
}
}
c = m_color_profile.last().color;
for(; end < m_color_lut.size(); end++)
{
m_color_lut[end] = c;
}
}
}
}
#endif
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