Improved comments.

[libdcp.git] / src / modified_gamma_transfer_function.h

diff --git a/src/modified_gamma_transfer_function.h b/src/modified_gamma_transfer_function.h
index 0c6a6b8429f25869e20e7f7981169bcaa4b5bdfd..70018cbf6be197529508f3dcd2d15c9a7d1c011a 100644 (file)
--- a/src/modified_gamma_transfer_function.h
+++ b/src/modified_gamma_transfer_function.h
@@ -1,62 +1,90 @@
 /*
-    Copyright (C) 2012-2014 Carl Hetherington <cth@carlh.net>
+    Copyright (C) 2012-2021 Carl Hetherington <cth@carlh.net>
 
-    This program is free software; you can redistribute it and/or modify
+    This file is part of libdcp.
+
+    libdcp 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,
+    libdcp 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.
+    along with libdcp.  If not, see <http://www.gnu.org/licenses/>.
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of portions of this program with the
+    OpenSSL library under certain conditions as described in each
+    individual source file, and distribute linked combinations
+    including the two.
 
+    You must obey the GNU General Public License in all respects
+    for all of the code used other than OpenSSL.  If you modify
+    file(s) with this exception, you may extend this exception to your
+    version of the file(s), but you are not obligated to do so.  If you
+    do not wish to do so, delete this exception statement from your
+    version.  If you delete this exception statement from all source
+    files in the program, then also delete it here.
 */
 
+
+/** @file  src/modified_gamma_transfer_function.h
+ *  @brief ModifiedGammaTransferFunction class
+ */
+
+
 #include "transfer_function.h"
 
+
 namespace dcp {
 
-/** A transfer function which for an input x gives an output y where
+
+/** A transfer function which for an input x gives a linear output y where
  *
  *  y = x / B                      for x <= threshold
  *  y = ((x + A) / (1 + A))^power  for x >  threshold
+ *
+ *  The reverse transform is
+ *
+ *  x = y * B                          for y <= threshold / B
+ *  x = (1 + A) * y ^ (1 / power) - A  for y >  threshold / B
  */
 class ModifiedGammaTransferFunction : public TransferFunction
 {
 public:
-       ModifiedGammaTransferFunction (float power, float threshold, float A, float B);
+       ModifiedGammaTransferFunction (double power, double threshold, double A, double B);
 
-       float power () const {
+       double power () const {
                return _power;
        }
 
-       float threshold () const {
+       double threshold () const {
                return _threshold;
        }
 
-       float A () const {
+       double A () const {
                return _A;
        }
 
-       float B () const {
+       double B () const {
                return _B;
        }
 
-       bool about_equal (boost::shared_ptr<const TransferFunction>, float epsilon) const;
-       
+       bool about_equal (std::shared_ptr<const TransferFunction>, double epsilon) const;
+
 protected:
-       float * make_lut (int bit_depth) const;
-       
+       double * make_lut (int bit_depth, bool inverse) const;
+
 private:
-       float _power;
-       float _threshold;
-       float _A;
-       float _B;
+       double _power;
+       double _threshold;
+       double _A;
+       double _B;
 };
 
+
 }