avutil: Extract gamma determination from PNG encoder for future use. Adds private avpriv_get_gamma_from_trc() function to libavutil.

Signed-off-by: Kevin Wheatley <kevin.j.wheatley@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 39 insertions, 0 deletions

diff --git a/libavutil/color_utils.h b/libavutil/color_utils.h
new file mode 100644
index 0000000000..3600a72d10
--- /dev/null
+++ b/libavutil/color_utils.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2015 Kevin Wheatley <kevin.j.wheatley@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_COLOR_UTILS_H
+#define AVUTIL_COLOR_UTILS_H
+
+
+#include "libavutil/pixfmt.h"
+
+/**
+ * Determine a suitable 'gamma' value to match the supplied
+ * AVColorTransferCharacteristic.
+ *
+ * See Apple Technical Note TN2257 (https://developer.apple.com/library/mac/technotes/tn2257/_index.html)
+ *
+ * @return Will return an approximation to the simple gamma function matching
+ *         the supplied Transfer Characteristic, Will return 0.0 for any
+ *         we cannot reasonably match against.
+ */
+double avpriv_get_gamma_from_trc(enum AVColorTransferCharacteristic trc);
+
+#endif