git.sesse.net Git - movit/blob - gamma_expansion_effect.cpp

   1 #include <math.h>
   2 #include <assert.h>
   3
   4 #include "gamma_expansion_effect.h"
   5 #include "util.h"
   6
   7 GammaExpansionEffect::GammaExpansionEffect()
   8         : source_curve(GAMMA_LINEAR)
   9 {
  10         register_int("source_curve", (int *)&source_curve);
  11         memset(expansion_curve, 0, sizeof(expansion_curve));
  12         register_1d_texture("expansion_curve_tex", expansion_curve, EXPANSION_CURVE_SIZE);
  13 }
  14
  15 std::string GammaExpansionEffect::output_fragment_shader()
  16 {
  17         if (source_curve == GAMMA_LINEAR) {
  18                 return read_file("identity.frag");
  19         }
  20         if (source_curve == GAMMA_sRGB) {
  21                 for (unsigned i = 0; i < EXPANSION_CURVE_SIZE; ++i) {
  22                         float x = i / (float)(EXPANSION_CURVE_SIZE - 1);
  23                         if (x < 0.04045f) {
  24                                 expansion_curve[i] = (1.0/12.92f) * x;
  25                         } else {
  26                                 expansion_curve[i] = pow((x + 0.055) * (1.0/1.055f), 2.4);
  27                         }
  28                 }
  29                 invalidate_1d_texture("expansion_curve_tex");
  30                 return read_file("gamma_expansion_effect.frag");
  31         }
  32         if (source_curve == GAMMA_REC_709 ||  // Also includes Rec. 601, and 10-bit Rec. 2020.
  33             source_curve == GAMMA_REC_2020_12_BIT) {
  34                 // Rec. 2020, page 3.
  35                 float alpha, beta;
  36                 if (source_curve == GAMMA_REC_2020_12_BIT) {
  37                         alpha = 1.0993f;
  38                         beta = 0.0181f;
  39                 } else {
  40                         alpha = 1.099f;
  41                         beta = 0.018f;
  42                 }
  43                 for (unsigned i = 0; i < EXPANSION_CURVE_SIZE; ++i) {
  44                         float x = i / (float)(EXPANSION_CURVE_SIZE - 1);
  45                         if (x < beta * 4.5f) {
  46                                 expansion_curve[i] = (1.0/4.5f) * x;
  47                         } else {
  48                                 expansion_curve[i] = pow((x + (alpha - 1.0f)) / alpha, 1.0f/0.45f);
  49                         }
  50                 }
  51                 invalidate_1d_texture("expansion_curve_tex");
  52                 return read_file("gamma_expansion_effect.frag");
  53         }
  54         assert(false);
  55 }