56 lines
1.4 KiB
GLSL
56 lines
1.4 KiB
GLSL
// https://www.arib.or.jp/kikaku/kikaku_hoso/std-b67.html
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// https://www.bbc.co.uk/rd/projects/high-dynamic-range
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// https://www.itu.int/rec/R-REC-BT.2100
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//!PARAM reference_white
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//!TYPE float
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//!MINIMUM 0.0
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//!MAXIMUM 1000.0
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203.0
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//!HOOK OUTPUT
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//!BIND HOOKED
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//!DESC transfer function (hlg, inverse)
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const vec3 y_coef = vec3(0.2627002120112671, 0.6779980715188708, 0.05930171646986196);
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const float Lw = 1000.0;
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const float Lb = 0.0;
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const float Lamb = 5.0;
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const float gamma = 1.2 + 0.42 * log(Lw / 1000.0) / log(10.0) - 0.076 * log(Lamb / 5.0) / log(10.0);
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const float alpha = Lw;
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const float beta = sqrt(3.0 * pow((Lb / Lw), 1.0 / gamma));
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const float a = 0.17883277;
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const float b = 1.0 - 4.0 * a;
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const float c = 0.5 - a * log(4.0 * a);
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float hlg_oetf_inv(float x) {
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return x <= 1.0 / 2.0 ? pow(x, 2.0) / 3.0 : (exp((x - c) / a) + b) / 12.0;
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}
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vec3 hlg_oetf_inv(vec3 color) {
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return vec3(
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hlg_oetf_inv(color.r),
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hlg_oetf_inv(color.g),
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hlg_oetf_inv(color.b)
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);
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}
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vec3 hlg_ootf(vec3 color) {
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float Y = dot(color, y_coef);
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return alpha * pow(Y, gamma - 1.0) * color;
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}
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vec3 hlg_eotf(vec3 color) {
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return hlg_ootf(hlg_oetf_inv(max((1.0 - beta) * color + beta, 0.0)));
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}
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vec4 hook() {
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vec4 color = HOOKED_tex(HOOKED_pos);
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color.rgb = hlg_eotf(color.rgb) / reference_white;
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return color;
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}
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