bsnes/higan/fc/system/video.cpp

auto System::configureVideo() -> void {
  Emulator::video.reset();
  Emulator::video.setInterface(interface);
  configureVideoPalette();
}

auto System::configureVideoPalette() -> void {
  auto generateColor = [](uint n, double saturation, double hue, double contrast, double brightness, double gamma) -> uint64 {
    int color = (n & 0x0f), level = color < 0xe ? (n >> 4) & 3 : 1;

    static const double black = 0.518, white = 1.962, attenuation = 0.746;
    static const double levels[8] = {
      0.350, 0.518, 0.962, 1.550,
      1.094, 1.506, 1.962, 1.962,
    };

    double lo_and_hi[2] = {
      levels[level + 4 * (color == 0x0)],
      levels[level + 4 * (color <  0xd)],
    };

    double y = 0.0, i = 0.0, q = 0.0;
    auto wave = [](int p, int color) { return (color + p + 8) % 12 < 6; };
    for(int p : range(12)) {
      double spot = lo_and_hi[wave(p, color)];

      if(((n & 0x040) && wave(p, 12))
      || ((n & 0x080) && wave(p,  4))
      || ((n & 0x100) && wave(p,  8))
      ) spot *= attenuation;

      double v = (spot - black) / (white - black);

      v = (v - 0.5) * contrast + 0.5;
      v *= brightness / 12.0;

      y += v;
      i += v * std::cos((3.141592653 / 6.0) * (p + hue));
      q += v * std::sin((3.141592653 / 6.0) * (p + hue));
    }

    i *= saturation;
    q *= saturation;

    auto gammaAdjust = [=](double f) { return f < 0.0 ? 0.0 : std::pow(f, 2.2 / gamma); };
    uint64 r = uclamp<16>(65535.0 * gammaAdjust(y +  0.946882 * i +  0.623557 * q));
    uint64 g = uclamp<16>(65535.0 * gammaAdjust(y + -0.274788 * i + -0.635691 * q));
    uint64 b = uclamp<16>(65535.0 * gammaAdjust(y + -1.108545 * i +  1.709007 * q));

    return r << 32 | g << 16 | b << 0;
  };

  Emulator::video.setPalette(1 << 9, [&](uint32 color) -> uint64 {
    auto gamma = settings.colorEmulation ? 1.8 : 2.2;
    return generateColor(color, 2.0, 0.0, 1.0, 1.0, gamma);
  });
}