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/*
Copyright (C) 2012-2014 Carl Hetherington <cth@carlh.net>
This program 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.
This program 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 this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "gamma_transfer_function.h"
#include <cmath>
using std::pow;
using boost::shared_ptr;
using boost::dynamic_pointer_cast;
using namespace dcp;
GammaTransferFunction::GammaTransferFunction (double gamma)
: _gamma (gamma)
{
}
double *
GammaTransferFunction::make_lut (int bit_depth, bool inverse) const
{
int const bit_length = int(std::pow(2.0f, bit_depth));
double* lut = new double[bit_length];
double const gamma = inverse ? (1 / _gamma) : _gamma;
for (int i = 0; i < bit_length; ++i) {
lut[i] = pow(double(i) / (bit_length - 1), gamma);
}
return lut;
}
bool
GammaTransferFunction::about_equal (shared_ptr<const TransferFunction> other, double epsilon) const
{
shared_ptr<const GammaTransferFunction> o = dynamic_pointer_cast<const GammaTransferFunction> (other);
if (!o) {
return false;
}
return fabs (_gamma - o->_gamma) < epsilon;
}
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