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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 <stddef.h>
#include <math.h>
#include "common.h"
#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;
}
#define BT709_alpha 1.099296826809442
#define BT709_beta 0.018053968510807
static double avpriv_trc_bt709(double Lc)
{
const double a = BT709_alpha;
const double b = BT709_beta;
return (0.0 > Lc) ? 0.0
: ( b > Lc) ? 4.500 * Lc
: a * pow(Lc, 0.45) - (a - 1.0);
}
static double avpriv_trc_gamma22(double Lc)
{
return (0.0 > Lc) ? 0.0 : pow(Lc, 1.0/ 2.2);
}
static double avpriv_trc_gamma28(double Lc)
{
return (0.0 > Lc) ? 0.0 : pow(Lc, 1.0/ 2.8);
}
static double avpriv_trc_smpte240M(double Lc)
{
const double a = 1.1115;
const double b = 0.0228;
return (0.0 > Lc) ? 0.0
: ( b > Lc) ? 4.000 * Lc
: a * pow(Lc, 0.45) - (a - 1.0);
}
static double avpriv_trc_linear(double Lc)
{
return Lc;
}
static double avpriv_trc_log(double Lc)
{
return (0.01 > Lc) ? 0.0 : 1.0 + log10(Lc) / 2.0;
}
static double avpriv_trc_log_sqrt(double Lc)
{
// sqrt(10) / 1000
return (0.00316227766 > Lc) ? 0.0 : 1.0 + log10(Lc) / 2.5;
}
static double avpriv_trc_iec61966_2_4(double Lc)
{
const double a = BT709_alpha;
const double b = BT709_beta;
return (-b >= Lc) ? -a * pow(-Lc, 0.45) + (a - 1.0)
: ( b > Lc) ? 4.500 * Lc
: a * pow( Lc, 0.45) - (a - 1.0);
}
static double avpriv_trc_bt1361(double Lc)
{
const double a = BT709_alpha;
const double b = BT709_beta;
return (-0.0045 >= Lc) ? -(a * pow(-4.0 * Lc, 0.45) + (a - 1.0)) / 4.0
: ( b > Lc) ? 4.500 * Lc
: a * pow( Lc, 0.45) - (a - 1.0);
}
static double avpriv_trc_iec61966_2_1(double Lc)
{
const double a = 1.055;
const double b = 0.0031308;
return (0.0 > Lc) ? 0.0
: ( b > Lc) ? 12.92 * Lc
: a * pow(Lc, 1.0 / 2.4) - (a - 1.0);
}
static double avpriv_trc_smpte_st2084(double Lc)
{
const double c1 = 3424.0 / 4096.0; // c3-c2 + 1
const double c2 = 32.0 * 2413.0 / 4096.0;
const double c3 = 32.0 * 2392.0 / 4096.0;
const double m = 128.0 * 2523.0 / 4096.0;
const double n = 0.25 * 2610.0 / 4096.0;
const double L = Lc / 10000.0;
const double Ln = pow(L, n);
return (0.0 > Lc) ? 0.0
: pow((c1 + c2 * Ln) / (1.0 + c3 * Ln), m);
}
static double avpriv_trc_smpte_st428_1(double Lc)
{
return (0.0 > Lc) ? 0.0
: pow(48.0 * Lc / 52.37, 1.0 / 2.6);
}
static double avpriv_trc_arib_std_b67(double Lc) {
// The function uses the definition from HEVC, which assumes that the peak
// white is input level = 1. (this is equivalent to scaling E = Lc * 12 and
// using the definition from the ARIB STD-B67 spec)
const double a = 0.17883277;
const double b = 0.28466892;
const double c = 0.55991073;
return (0.0 > Lc) ? 0.0 :
(Lc <= 1.0 / 12.0 ? sqrt(3.0 * Lc) : a * log(12.0 * Lc - b) + c);
}
avpriv_trc_function avpriv_get_trc_function_from_trc(enum AVColorTransferCharacteristic trc)
{
avpriv_trc_function func = NULL;
switch (trc) {
case AVCOL_TRC_BT709:
case AVCOL_TRC_SMPTE170M:
case AVCOL_TRC_BT2020_10:
case AVCOL_TRC_BT2020_12:
func = avpriv_trc_bt709;
break;
case AVCOL_TRC_GAMMA22:
func = avpriv_trc_gamma22;
break;
case AVCOL_TRC_GAMMA28:
func = avpriv_trc_gamma28;
break;
case AVCOL_TRC_SMPTE240M:
func = avpriv_trc_smpte240M;
break;
case AVCOL_TRC_LINEAR:
func = avpriv_trc_linear;
break;
case AVCOL_TRC_LOG:
func = avpriv_trc_log;
break;
case AVCOL_TRC_LOG_SQRT:
func = avpriv_trc_log_sqrt;
break;
case AVCOL_TRC_IEC61966_2_4:
func = avpriv_trc_iec61966_2_4;
break;
case AVCOL_TRC_BT1361_ECG:
func = avpriv_trc_bt1361;
break;
case AVCOL_TRC_IEC61966_2_1:
func = avpriv_trc_iec61966_2_1;
break;
case AVCOL_TRC_SMPTEST2084:
func = avpriv_trc_smpte_st2084;
break;
case AVCOL_TRC_SMPTEST428_1:
func = avpriv_trc_smpte_st428_1;
break;
case AVCOL_TRC_ARIB_STD_B67:
func = avpriv_trc_arib_std_b67;
break;
case AVCOL_TRC_RESERVED0:
case AVCOL_TRC_UNSPECIFIED:
case AVCOL_TRC_RESERVED:
default:
break;
}
return func;
}
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