X-Git-Url: https://git.carlh.net/gitweb/?a=blobdiff_plain;f=src%2Fmodified_gamma_transfer_function.h;h=f0448158c39de3affaccd69bdb4651a04cb80d93;hb=d4b350cc524543b8142ac803232b31af751885e2;hp=2a7a7b59ba4b443be7fa52259e9309320f8dac23;hpb=1c17602bfc56abbf17c1e974f99477655627725b;p=libdcp.git

diff --git a/src/modified_gamma_transfer_function.h b/src/modified_gamma_transfer_function.h
index 2a7a7b59..f0448158 100644
--- a/src/modified_gamma_transfer_function.h
+++ b/src/modified_gamma_transfer_function.h
@@ -1,20 +1,34 @@
 /*
     Copyright (C) 2012-2014 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
@@ -25,10 +39,15 @@
 
 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
 {
@@ -52,10 +71,10 @@ public:
 	}
 
 	bool about_equal (boost::shared_ptr<const TransferFunction>, double epsilon) const;
-	
+
 protected:
 	double * make_lut (int bit_depth, bool inverse) const;
-	
+
 private:
 	double _power;
 	double _threshold;