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avutil/{color_utils, csp}: merge color_utils into csp and expose API

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libavutil/color_utils contains some avpriv_ symbols that map
enum AVTransferCharacteristic values to gamma-curve approximations and
to the actual transfer functions to invert them (i.e. -> linear).

There's two issues with this:
(1) avpriv is evil and should be avoided whenever possible
(2) libavutil/csp.h exposes a public API for handling color that
    already handles primaries and matricies

I don't see any reason this API has to be private, so this commit takes
the functionality from avutil/color_utils and merges it into avutil/csp
with an exposed av_ API rather than the previous avpriv_ API.

Every reference to the previous API has been updated to point to the
new one. color_utils.h has been deleted as well. This should not break
any applications as it only contained avpriv_ symbols in the first
place, so nothing in that header could be referenced by other
applications.

Signed-off-by: Leo Izen <leo.izen@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
This commit is contained in:
Leo Izen 2023-01-30 11:50:10 -05:00 • committed by Anton Khirnov
parent dc1b8135e0
commit 719a93f4e4
11 changed files with 225 additions and 304 deletions
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4
doc/APIchanges
View file

@ -14,6 +14,10 @@ libavutil: 2021-04-27
API changes, most recent first: API changes, most recent first:
2023-02-xx - xxxxxxxxxx - lavu 58.0.100 - csp.h
Add av_csp_approximate_trc_gamma() and av_csp_trc_func_from_id().
Add av_csp_trc_function.
2023-02-xx - xxxxxxxxxx - lavc 60.0.100 - avcodec.h 2023-02-xx - xxxxxxxxxx - lavc 60.0.100 - avcodec.h
avcodec_decode_subtitle2() now accepts const AVPacket*. avcodec_decode_subtitle2() now accepts const AVPacket*.

8
libavcodec/exr.c
View file

@ -36,11 +36,11 @@
#include "libavutil/avassert.h" #include "libavutil/avassert.h"
#include "libavutil/common.h" #include "libavutil/common.h"
#include "libavutil/csp.h"
#include "libavutil/imgutils.h" #include "libavutil/imgutils.h"
#include "libavutil/intfloat.h" #include "libavutil/intfloat.h"
#include "libavutil/avstring.h" #include "libavutil/avstring.h"
#include "libavutil/opt.h" #include "libavutil/opt.h"
#include "libavutil/color_utils.h"
#include "libavutil/half2float.h" #include "libavutil/half2float.h"
#include "avcodec.h" #include "avcodec.h"
@ -1189,7 +1189,7 @@ static int decode_block(AVCodecContext *avctx, void *tdata,
int i, x, buf_size = s->buf_size; int i, x, buf_size = s->buf_size;
int c, rgb_channel_count; int c, rgb_channel_count;
float one_gamma = 1.0f / s->gamma; float one_gamma = 1.0f / s->gamma;
avpriv_trc_function trc_func = avpriv_get_trc_function_from_trc(s->apply_trc_type); av_csp_trc_function trc_func = av_csp_trc_func_from_id(s->apply_trc_type);
int ret; int ret;
line_offset = AV_RL64(s->gb.buffer + jobnr * 8); line_offset = AV_RL64(s->gb.buffer + jobnr * 8);
@ -2215,7 +2215,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
uint32_t i; uint32_t i;
union av_intfloat32 t; union av_intfloat32 t;
float one_gamma = 1.0f / s->gamma; float one_gamma = 1.0f / s->gamma;
avpriv_trc_function trc_func = NULL; av_csp_trc_function trc_func = NULL;
ff_init_half2float_tables(&s->h2f_tables); ff_init_half2float_tables(&s->h2f_tables);
@ -2227,7 +2227,7 @@ static av_cold int decode_init(AVCodecContext *avctx)
ff_bswapdsp_init(&s->bbdsp); ff_bswapdsp_init(&s->bbdsp);
#endif #endif
trc_func = avpriv_get_trc_function_from_trc(s->apply_trc_type); trc_func = av_csp_trc_func_from_id(s->apply_trc_type);
if (trc_func) { if (trc_func) {
for (i = 0; i < 65536; ++i) { for (i = 0; i < 65536; ++i) {
t.i = half2float(i, &s->h2f_tables); t.i = half2float(i, &s->h2f_tables);

1
libavcodec/fflcms2.c
View file

@ -17,7 +17,6 @@
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/ */
#include "libavutil/color_utils.h"
#include "libavutil/csp.h" #include "libavutil/csp.h"
#include "fflcms2.h" #include "fflcms2.h"

3
libavcodec/pngenc.c
View file

@ -29,7 +29,6 @@
#include "zlib_wrapper.h" #include "zlib_wrapper.h"
#include "libavutil/avassert.h" #include "libavutil/avassert.h"
#include "libavutil/color_utils.h"
#include "libavutil/crc.h" #include "libavutil/crc.h"
#include "libavutil/csp.h" #include "libavutil/csp.h"
#include "libavutil/libm.h" #include "libavutil/libm.h"
@ -317,7 +316,7 @@ static int png_get_chrm(enum AVColorPrimaries prim, uint8_t *buf)
static int png_get_gama(enum AVColorTransferCharacteristic trc, uint8_t *buf) static int png_get_gama(enum AVColorTransferCharacteristic trc, uint8_t *buf)
{ {
double gamma = avpriv_get_gamma_from_trc(trc); double gamma = av_csp_approximate_trc_gamma(trc);
if (gamma <= 1e-6) if (gamma <= 1e-6)
return 0; return 0;

7
libavformat/movenc.c
View file

@ -47,6 +47,7 @@
#include "internal.h" #include "internal.h"
#include "libavutil/avstring.h" #include "libavutil/avstring.h"
#include "libavutil/channel_layout.h" #include "libavutil/channel_layout.h"
#include "libavutil/csp.h"
#include "libavutil/intfloat.h" #include "libavutil/intfloat.h"
#include "libavutil/mathematics.h" #include "libavutil/mathematics.h"
#include "libavutil/libm.h" #include "libavutil/libm.h"
@ -56,7 +57,6 @@
#include "libavutil/stereo3d.h" #include "libavutil/stereo3d.h"
#include "libavutil/timecode.h" #include "libavutil/timecode.h"
#include "libavutil/dovi_meta.h" #include "libavutil/dovi_meta.h"
#include "libavutil/color_utils.h"
#include "libavutil/uuid.h" #include "libavutil/uuid.h"
#include "hevc.h" #include "hevc.h"
#include "rtpenc.h" #include "rtpenc.h"
@ -2011,9 +2011,8 @@ static int mov_write_pasp_tag(AVIOContext *pb, MOVTrack *track)
static int mov_write_gama_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *track, double gamma) static int mov_write_gama_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *track, double gamma)
{ {
uint32_t gama = 0; uint32_t gama = 0;
if (gamma <= 0.0) { if (gamma <= 0.0)
gamma = avpriv_get_gamma_from_trc(track->par->color_trc); gamma = av_csp_approximate_trc_gamma(track->par->color_trc);
}
av_log(s, AV_LOG_DEBUG, "gamma value %g\n", gamma); av_log(s, AV_LOG_DEBUG, "gamma value %g\n", gamma);
if (gamma > 1e-6) { if (gamma > 1e-6) {

1
libavutil/Makefile
View file

@ -114,7 +114,6 @@ OBJS = adler32.o \
cast5.o \ cast5.o \
camellia.o \ camellia.o \
channel_layout.o \ channel_layout.o \
color_utils.o \
cpu.o \ cpu.o \
crc.o \ crc.o \
csp.o \ csp.o \

234
libavutil/color_utils.c
View file

@ -1,234 +0,0 @@
/*
* 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 "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;
}

56
libavutil/color_utils.h
View file

@ -1,56 +0,0 @@
/*
* 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);
typedef double (*avpriv_trc_function)(double);
/**
* Determine the function needed to apply the given
* AVColorTransferCharacteristic to linear input.
*
* The function returned should expect a nominal domain and range of [0.0-1.0]
* values outside of this range maybe valid depending on the chosen
* characteristic function.
*
* @return Will return pointer to the function matching the
* supplied Transfer Characteristic. If unspecified will
* return NULL:
*/
avpriv_trc_function avpriv_get_trc_function_from_trc(enum AVColorTransferCharacteristic trc);
#endif

172
libavutil/csp.c
View file

@ -1,5 +1,8 @@
/* /*
* Copyright (c) 2015 Kevin Wheatley <kevin.j.wheatley@gmail.com>
* Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com> * Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com>
* Copyright (c) 2023 Leo Izen <leo.izen@gmail.com>
*
* This file is part of FFmpeg. * This file is part of FFmpeg.
* *
* FFmpeg is free software; you can redistribute it and/or * FFmpeg is free software; you can redistribute it and/or
@ -21,9 +24,11 @@
* @file Colorspace functions for libavutil * @file Colorspace functions for libavutil
* @author Ronald S. Bultje <rsbultje@gmail.com> * @author Ronald S. Bultje <rsbultje@gmail.com>
* @author Leo Izen <leo.izen@gmail.com> * @author Leo Izen <leo.izen@gmail.com>
* @author Kevin Wheatley <kevin.j.wheatley@gmail.com>
*/ */
#include <stdlib.h> #include <stdlib.h>
#include <math.h>
#include "attributes.h" #include "attributes.h"
#include "csp.h" #include "csp.h"
@ -126,3 +131,170 @@ enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *
return AVCOL_PRI_UNSPECIFIED; return AVCOL_PRI_UNSPECIFIED;
} }
static const double approximate_gamma[AVCOL_TRC_NB] = {
[AVCOL_TRC_BT709] = 1.961,
[AVCOL_TRC_SMPTE170M] = 1.961,
[AVCOL_TRC_SMPTE240M] = 1.961,
[AVCOL_TRC_BT1361_ECG] = 1.961,
[AVCOL_TRC_BT2020_10] = 1.961,
[AVCOL_TRC_BT2020_12] = 1.961,
[AVCOL_TRC_GAMMA22] = 2.2,
[AVCOL_TRC_IEC61966_2_1] = 2.2,
[AVCOL_TRC_GAMMA28] = 2.8,
[AVCOL_TRC_LINEAR] = 1.0,
[AVCOL_TRC_SMPTE428] = 2.6,
};
double av_csp_approximate_trc_gamma(enum AVColorTransferCharacteristic trc)
{
double gamma;
if (trc >= AVCOL_TRC_NB)
return 0.0;
gamma = approximate_gamma[trc];
if (gamma > 0)
return gamma;
return 0.0;
}
#define BT709_alpha 1.099296826809442
#define BT709_beta 0.018053968510807
static double 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 trc_gamma22(double Lc)
{
return (0.0 > Lc) ? 0.0 : pow(Lc, 1.0/ 2.2);
}
static double trc_gamma28(double Lc)
{
return (0.0 > Lc) ? 0.0 : pow(Lc, 1.0/ 2.8);
}
static double 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 trc_linear(double Lc)
{
return Lc;
}
static double trc_log(double Lc)
{
return (0.01 > Lc) ? 0.0 : 1.0 + log10(Lc) / 2.0;
}
static double trc_log_sqrt(double Lc)
{
// sqrt(10) / 1000
return (0.00316227766 > Lc) ? 0.0 : 1.0 + log10(Lc) / 2.5;
}
static double 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 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 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 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 trc_smpte_st428_1(double Lc)
{
return (0.0 > Lc) ? 0.0
: pow(48.0 * Lc / 52.37, 1.0 / 2.6);
}
static double 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);
}
static const av_csp_trc_function trc_funcs[AVCOL_TRC_NB] = {
[AVCOL_TRC_BT709] = trc_bt709,
[AVCOL_TRC_GAMMA22] = trc_gamma22,
[AVCOL_TRC_GAMMA28] = trc_gamma28,
[AVCOL_TRC_SMPTE170M] = trc_bt709,
[AVCOL_TRC_SMPTE240M] = trc_smpte240M,
[AVCOL_TRC_LINEAR] = trc_linear,
[AVCOL_TRC_LOG] = trc_log,
[AVCOL_TRC_LOG_SQRT] = trc_log_sqrt,
[AVCOL_TRC_IEC61966_2_4] = trc_iec61966_2_4,
[AVCOL_TRC_BT1361_ECG] = trc_bt1361,
[AVCOL_TRC_IEC61966_2_1] = trc_iec61966_2_1,
[AVCOL_TRC_BT2020_10] = trc_bt709,
[AVCOL_TRC_BT2020_12] = trc_bt709,
[AVCOL_TRC_SMPTE2084] = trc_smpte_st2084,
[AVCOL_TRC_SMPTE428] = trc_smpte_st428_1,
[AVCOL_TRC_ARIB_STD_B67] = trc_arib_std_b67,
};
av_csp_trc_function av_csp_trc_func_from_id(enum AVColorTransferCharacteristic trc)
{
av_csp_trc_function func;
if (trc >= AVCOL_TRC_NB)
return NULL;
func = trc_funcs[trc];
if (!func)
return NULL;
return func;
}

39
libavutil/csp.h
View file

@ -1,5 +1,8 @@
/* /*
* Copyright (c) 2015 Kevin Wheatley <kevin.j.wheatley@gmail.com>
* Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com> * Copyright (c) 2016 Ronald S. Bultje <rsbultje@gmail.com>
* Copyright (c) 2023 Leo Izen <leo.izen@gmail.com>
*
* This file is part of FFmpeg. * This file is part of FFmpeg.
* *
* FFmpeg is free software; you can redistribute it and/or * FFmpeg is free software; you can redistribute it and/or
@ -29,6 +32,7 @@
* @ingroup lavu_math_csp * @ingroup lavu_math_csp
* @author Ronald S. Bultje <rsbultje@gmail.com> * @author Ronald S. Bultje <rsbultje@gmail.com>
* @author Leo Izen <leo.izen@gmail.com> * @author Leo Izen <leo.izen@gmail.com>
* @author Kevin Wheatley <kevin.j.wheatley@gmail.com>
*/ */
/** /**
@ -76,6 +80,12 @@ typedef struct AVColorPrimariesDesc {
AVPrimaryCoefficients prim; AVPrimaryCoefficients prim;
} AVColorPrimariesDesc; } AVColorPrimariesDesc;
/**
* Function pointer representing a double -> double transfer function that performs
* an EOTF transfer inversion. This function outputs linear light.
*/
typedef double (*av_csp_trc_function)(double);
/** /**
* Retrieves the Luma coefficients necessary to construct a conversion matrix * Retrieves the Luma coefficients necessary to construct a conversion matrix
* from an enum constant describing the colorspace. * from an enum constant describing the colorspace.
@ -104,6 +114,35 @@ const AVColorPrimariesDesc *av_csp_primaries_desc_from_id(enum AVColorPrimaries
*/ */
enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *prm); enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *prm);
/**
* 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)
*
* This function returns the gamma exponent for the OETF. For example, sRGB is approximated
* by gamma 2.2, not by gamma 0.45455.
*
* @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 av_csp_approximate_trc_gamma(enum AVColorTransferCharacteristic trc);
/**
* Determine the function needed to apply the given
* AVColorTransferCharacteristic to linear input.
*
* The function returned should expect a nominal domain and range of [0.0-1.0]
* values outside of this range maybe valid depending on the chosen
* characteristic function.
*
* @return Will return pointer to the function matching the
* supplied Transfer Characteristic. If unspecified will
* return NULL:
*/
av_csp_trc_function av_csp_trc_func_from_id(enum AVColorTransferCharacteristic trc);
/** /**
* @} * @}
*/ */

4
libavutil/tests/color_utils.c
View file

@ -19,7 +19,7 @@
*/ */
#include <stdio.h> #include <stdio.h>
#include "libavutil/color_utils.c" #include "libavutil/csp.h"
#include "libavutil/macros.h" #include "libavutil/macros.h"
int main(int argc, char *argv[]) int main(int argc, char *argv[])
@ -32,7 +32,7 @@ int main(int argc, char *argv[])
}; };
for(i = 0; i < AVCOL_TRC_NB; i++) { for(i = 0; i < AVCOL_TRC_NB; i++) {
avpriv_trc_function func = avpriv_get_trc_function_from_trc(i); av_csp_trc_function func = av_csp_trc_func_from_id(i);
for(j = 0; j < FF_ARRAY_ELEMS(test_data); j++) { for(j = 0; j < FF_ARRAY_ELEMS(test_data); j++) {
if(func != NULL) { if(func != NULL) {
double result = func(test_data[j]); double result = func(test_data[j]);