FFmpeg/libavutil/csp.c

/*
 * Copyright (c) 2015 Kevin Wheatley <kevin.j.wheatley@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.
 *
 * 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
 */

/**
 * @file Colorspace functions for libavutil
 * @author Ronald S. Bultje <rsbultje@gmail.com>
 * @author Leo Izen <leo.izen@gmail.com>
 * @author Kevin Wheatley <kevin.j.wheatley@gmail.com>
 */

#include <stdlib.h>
#include <math.h>

#include "attributes.h"
#include "csp.h"
#include "pixfmt.h"
#include "rational.h"

#define AVR(d) { (int)(d * 100000 + 0.5), 100000 }

/*
 * All constants explained in e.g. https://linuxtv.org/downloads/v4l-dvb-apis/ch02s06.html
 * The older ones (bt470bg/m) are also explained in their respective ITU docs
 * (e.g. https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.470-5-199802-S!!PDF-E.pdf)
 * whereas the newer ones can typically be copied directly from wikipedia :)
 */
static const struct AVLumaCoefficients luma_coefficients[AVCOL_SPC_NB] = {
    [AVCOL_SPC_FCC]        = { AVR(0.30),   AVR(0.59),   AVR(0.11)   },
    [AVCOL_SPC_BT470BG]    = { AVR(0.299),  AVR(0.587),  AVR(0.114)  },
    [AVCOL_SPC_SMPTE170M]  = { AVR(0.299),  AVR(0.587),  AVR(0.114)  },
    [AVCOL_SPC_BT709]      = { AVR(0.2126), AVR(0.7152), AVR(0.0722) },
    [AVCOL_SPC_SMPTE240M]  = { AVR(0.212),  AVR(0.701),  AVR(0.087)  },
    [AVCOL_SPC_YCOCG]      = { AVR(0.25),   AVR(0.5),    AVR(0.25)   },
    [AVCOL_SPC_RGB]        = { AVR(1),      AVR(1),      AVR(1)      },
    [AVCOL_SPC_BT2020_NCL] = { AVR(0.2627), AVR(0.6780), AVR(0.0593) },
    [AVCOL_SPC_BT2020_CL]  = { AVR(0.2627), AVR(0.6780), AVR(0.0593) },
};

const struct AVLumaCoefficients *av_csp_luma_coeffs_from_avcsp(enum AVColorSpace csp)
{
    const AVLumaCoefficients *coeffs;

    if (csp >= AVCOL_SPC_NB)
        return NULL;
    coeffs = &luma_coefficients[csp];
    if (!coeffs->cr.num)
        return NULL;

    return coeffs;
}

#define WP_D65 { AVR(0.3127), AVR(0.3290) }
#define WP_C   { AVR(0.3100), AVR(0.3160) }
#define WP_DCI { AVR(0.3140), AVR(0.3510) }
#define WP_E   { {1, 3}, {1, 3} }

static const AVColorPrimariesDesc color_primaries[AVCOL_PRI_NB] = {
    [AVCOL_PRI_BT709]     = { WP_D65, { { AVR(0.640), AVR(0.330) }, { AVR(0.300), AVR(0.600) }, { AVR(0.150), AVR(0.060) } } },
    [AVCOL_PRI_BT470M]    = { WP_C,   { { AVR(0.670), AVR(0.330) }, { AVR(0.210), AVR(0.710) }, { AVR(0.140), AVR(0.080) } } },
    [AVCOL_PRI_BT470BG]   = { WP_D65, { { AVR(0.640), AVR(0.330) }, { AVR(0.290), AVR(0.600) }, { AVR(0.150), AVR(0.060) } } },
    [AVCOL_PRI_SMPTE170M] = { WP_D65, { { AVR(0.630), AVR(0.340) }, { AVR(0.310), AVR(0.595) }, { AVR(0.155), AVR(0.070) } } },
    [AVCOL_PRI_SMPTE240M] = { WP_D65, { { AVR(0.630), AVR(0.340) }, { AVR(0.310), AVR(0.595) }, { AVR(0.155), AVR(0.070) } } },
    [AVCOL_PRI_SMPTE428]  = { WP_E,   { { AVR(0.735), AVR(0.265) }, { AVR(0.274), AVR(0.718) }, { AVR(0.167), AVR(0.009) } } },
    [AVCOL_PRI_SMPTE431]  = { WP_DCI, { { AVR(0.680), AVR(0.320) }, { AVR(0.265), AVR(0.690) }, { AVR(0.150), AVR(0.060) } } },
    [AVCOL_PRI_SMPTE432]  = { WP_D65, { { AVR(0.680), AVR(0.320) }, { AVR(0.265), AVR(0.690) }, { AVR(0.150), AVR(0.060) } } },
    [AVCOL_PRI_FILM]      = { WP_C,   { { AVR(0.681), AVR(0.319) }, { AVR(0.243), AVR(0.692) }, { AVR(0.145), AVR(0.049) } } },
    [AVCOL_PRI_BT2020]    = { WP_D65, { { AVR(0.708), AVR(0.292) }, { AVR(0.170), AVR(0.797) }, { AVR(0.131), AVR(0.046) } } },
    [AVCOL_PRI_JEDEC_P22] = { WP_D65, { { AVR(0.630), AVR(0.340) }, { AVR(0.295), AVR(0.605) }, { AVR(0.155), AVR(0.077) } } },
};

const AVColorPrimariesDesc *av_csp_primaries_desc_from_id(enum AVColorPrimaries prm)
{
    const AVColorPrimariesDesc *p;

    if (prm >= AVCOL_PRI_NB)
        return NULL;
    p = &color_primaries[prm];
    if (!p->prim.r.x.num)
        return NULL;

    return p;
}

static av_always_inline AVRational abs_sub_q(AVRational r1, AVRational r2)
{
    AVRational diff = av_sub_q(r1, r2);
    /* denominator assumed to be positive */
    return av_make_q(abs(diff.num), diff.den);
}

enum AVColorPrimaries av_csp_primaries_id_from_desc(const AVColorPrimariesDesc *prm)
{
    AVRational delta;

    for (enum AVColorPrimaries p = 0; p < AVCOL_PRI_NB; p++) {
        const AVColorPrimariesDesc *ref = &color_primaries[p];
        if (!ref->prim.r.x.num)
            continue;

        delta = abs_sub_q(prm->prim.r.x, ref->prim.r.x);
        delta = av_add_q(delta, abs_sub_q(prm->prim.r.y, ref->prim.r.y));
        delta = av_add_q(delta, abs_sub_q(prm->prim.g.x, ref->prim.g.x));
        delta = av_add_q(delta, abs_sub_q(prm->prim.g.y, ref->prim.g.y));
        delta = av_add_q(delta, abs_sub_q(prm->prim.b.x, ref->prim.b.x));
        delta = av_add_q(delta, abs_sub_q(prm->prim.b.y, ref->prim.b.y));
        delta = av_add_q(delta, abs_sub_q(prm->wp.x, ref->wp.x));
        delta = av_add_q(delta, abs_sub_q(prm->wp.y, ref->wp.y));

        if (av_cmp_q(delta, av_make_q(1, 1000)) < 0)
            return p;
    }

    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;
}