/usr/include/agg2/agg_gamma_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_GAMMA_LUT_INCLUDED
#define AGG_GAMMA_LUT_INCLUDED
#include <math.h>
#include "agg_basics.h"
namespace agg
{
template<class LoResT=int8u,
class HiResT=int8u,
unsigned GammaShift=8,
unsigned HiResShift=8> class gamma_lut
{
public:
typedef gamma_lut<LoResT, HiResT, GammaShift, HiResShift> self_type;
enum gamma_scale_e
{
gamma_shift = GammaShift,
gamma_size = 1 << gamma_shift,
gamma_mask = gamma_size - 1
};
enum hi_res_scale_e
{
hi_res_shift = HiResShift,
hi_res_size = 1 << hi_res_shift,
hi_res_mask = hi_res_size - 1
};
~gamma_lut()
{
pod_allocator<LoResT>::deallocate(m_inv_gamma, hi_res_size);
pod_allocator<HiResT>::deallocate(m_dir_gamma, gamma_size);
}
gamma_lut() :
m_gamma(1.0),
m_dir_gamma(pod_allocator<HiResT>::allocate(gamma_size)),
m_inv_gamma(pod_allocator<LoResT>::allocate(hi_res_size))
{
unsigned i;
for(i = 0; i < gamma_size; i++)
{
m_dir_gamma[i] = HiResT(i << (hi_res_shift - gamma_shift));
}
for(i = 0; i < hi_res_size; i++)
{
m_inv_gamma[i] = LoResT(i >> (hi_res_shift - gamma_shift));
}
}
gamma_lut(double g) :
m_gamma(1.0),
m_dir_gamma(pod_allocator<HiResT>::allocate(gamma_size)),
m_inv_gamma(pod_allocator<LoResT>::allocate(hi_res_size))
{
gamma(g);
}
void gamma(double g)
{
m_gamma = g;
unsigned i;
for(i = 0; i < gamma_size; i++)
{
m_dir_gamma[i] = (HiResT)
uround(pow(i / double(gamma_mask), m_gamma) * double(hi_res_mask));
}
double inv_g = 1.0 / g;
for(i = 0; i < hi_res_size; i++)
{
m_inv_gamma[i] = (LoResT)
uround(pow(i / double(hi_res_mask), inv_g) * double(gamma_mask));
}
}
double gamma() const
{
return m_gamma;
}
HiResT dir(LoResT v) const
{
return m_dir_gamma[unsigned(v)];
}
LoResT inv(HiResT v) const
{
return m_inv_gamma[unsigned(v)];
}
private:
gamma_lut(const self_type&);
const self_type& operator = (const self_type&);
double m_gamma;
HiResT* m_dir_gamma;
LoResT* m_inv_gamma;
};
}
#endif
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