/*
  * 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;
 }