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

   1 #include <math.h>
   2 #include <string.h>
   3 #include <assert.h>
   4
   5 #include "gamma_compression_effect.h"
   6 #include "util.h"
   7
   8 GammaCompressionEffect::GammaCompressionEffect()
   9         : destination_curve(GAMMA_LINEAR)
  10 {
  11         register_int("destination_curve", (int *)&destination_curve);
  12         memset(compression_curve, 0, sizeof(compression_curve));
  13         register_1d_texture("compression_curve_tex", compression_curve, COMPRESSION_CURVE_SIZE);
  14 }
  15
  16 std::string GammaCompressionEffect::output_fragment_shader()
  17 {
  18         if (destination_curve == GAMMA_LINEAR) {
  19                 return read_file("identity.frag");
  20         }
  21         if (destination_curve == GAMMA_sRGB) {
  22                 for (unsigned i = 0; i < COMPRESSION_CURVE_SIZE; ++i) {
  23                         float x = i / (float)(COMPRESSION_CURVE_SIZE - 1);
  24                         if (x < 0.0031308f) {
  25                                 compression_curve[i] = 12.92f * x;
  26                         } else {
  27                                 compression_curve[i] = 1.055f * pow(x, 1.0f / 2.4f) - 0.055f;
  28                         }
  29                 }
  30                 invalidate_1d_texture("compression_curve_tex");
  31                 return read_file("gamma_compression_effect.frag");
  32         }
  33         if (destination_curve == GAMMA_REC_709 ||  // And Rec. 601, and 10-bit Rec. 2020.
  34             destination_curve == GAMMA_REC_2020_12_BIT) {
  35                 // Rec. 2020, page 3.
  36                 float alpha, beta;
  37                 if (destination_curve == GAMMA_REC_2020_12_BIT) {
  38                         alpha = 1.0993f;
  39                         beta = 0.0181f;
  40                 } else {
  41                         alpha = 1.099f;
  42                         beta = 0.018f;
  43                 }
  44                 for (unsigned i = 0; i < COMPRESSION_CURVE_SIZE; ++i) {
  45                         float x = i / (float)(COMPRESSION_CURVE_SIZE - 1);
  46                         if (x < beta) {
  47                                 compression_curve[i] = 4.5f * x;
  48                         } else {
  49                                 compression_curve[i] = alpha * pow(x, 0.45f) - (alpha - 1.0f);
  50                         }
  51                 }
  52                 invalidate_1d_texture("compression_curve_tex");
  53                 return read_file("gamma_compression_effect.frag");
  54         }
  55         assert(false);
  56 }