2 Copyright (C) 2012-2014 Carl Hetherington <cth@carlh.net>
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 #include "modified_gamma_transfer_function.h"
24 using boost::shared_ptr;
25 using boost::dynamic_pointer_cast;
28 ModifiedGammaTransferFunction::ModifiedGammaTransferFunction (bool inverse, double power, double threshold, double A, double B)
29 : TransferFunction (inverse)
31 , _threshold (threshold)
39 ModifiedGammaTransferFunction::make_lut (int bit_depth) const
41 int const bit_length = int(std::pow(2.0f, bit_depth));
42 double* lut = new double[bit_length];
44 double const threshold = _threshold / _B;
45 for (int i = 0; i < bit_length; ++i) {
46 double const p = static_cast<double> (i) / (bit_length - 1);
48 lut[i] = (1 + _A) * pow (p, 1 / _power) - _A;
54 for (int i = 0; i < bit_length; ++i) {
55 double const p = static_cast<double> (i) / (bit_length - 1);
57 lut[i] = pow ((p + _A) / (1 + _A), _power);
68 ModifiedGammaTransferFunction::about_equal (shared_ptr<const TransferFunction> other, double epsilon) const
70 if (!TransferFunction::about_equal (other, epsilon)) {
74 shared_ptr<const ModifiedGammaTransferFunction> o = dynamic_pointer_cast<const ModifiedGammaTransferFunction> (other);
80 fabs (_power - o->_power) < epsilon &&
81 fabs (_threshold - o->_threshold) < epsilon &&
82 fabs (_A - o->_A) < epsilon &&
83 fabs (_B - o->_B) < epsilon