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

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Signed-off-by: Kevin Wheatley <kevin.j.wheatley@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Kevin Wheatley 2015-03-05 10:37:51 +00:00 • committed by Michael Niedermayer
parent 6db20926c3
commit 86b59e6a50
5 changed files with 97 additions and 26 deletions
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52
libavutil/color_utils.c Normal file
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/*
* 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
*/
#include "libavutil/color_utils.h"
#include "libavutil/pixfmt.h"
double avpriv_get_gamma_from_trc(enum AVColorTransferCharacteristic trc)
{
double gamma;
switch (trc) {
case AVCOL_TRC_BT709:
case AVCOL_TRC_SMPTE170M:
case AVCOL_TRC_SMPTE240M:
case AVCOL_TRC_BT1361_ECG:
case AVCOL_TRC_BT2020_10:
case AVCOL_TRC_BT2020_12:
/* these share a segmented TRC, but gamma 1.961 is a close
approximation, and also more correct for decoding content */
gamma = 1.961;
break;
case AVCOL_TRC_GAMMA22:
case AVCOL_TRC_IEC61966_2_1:
gamma = 2.2;
break;
case AVCOL_TRC_GAMMA28:
gamma = 2.8;
break;
case AVCOL_TRC_LINEAR:
gamma = 1.0;
break;
default:
gamma = 0.0; // Unknown value representation
}
return gamma;
}