46 lines
1.5 KiB
Forth
46 lines
1.5 KiB
Forth
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#define lerp(a,b,c) mix(a,b,c)
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#define saturate(c) clamp(c, 0.0, 1.0)
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// This function approximates the black and white film stock
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// "Ilford FP4" pushed to 400 ISO. It is typical for noir style. This
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// tonal transformation does not approximate gamma 2.2, so an explicit
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// sRGB transform should be performed before display.
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//
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// vec3 hdr (IN): Color pixel in linear space
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// vec2 uv (IN): Screen space UV for vignette
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//
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// returns Filmic remapped pixel in gamma 1.0 space
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// src: pic.twitter.com/7ZSMM5RRMz
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//
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vec3 PostFilmic_IlfordFp4Push(vec3 c, vec2 uv) {
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// film curve coefficients
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const vec3 cb = vec3( 0.0307479, 0.00030400, -0.04458630);
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const vec3 de = vec3(-0.0095000, -0.00162400, -0.01736670);
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const vec3 df = vec3( 0.1493590, 0.21412400, 1.85780000);
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const vec3 ef = vec3(-0.0636051, -0.00758438, -0.00934798);
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c = c * c * 1.88; // quick approximation of skip bleach
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// remap color channels
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vec3 ax = vec3(2.36691,5.14272,0.49020)*c;
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vec3 pn = (c*(ax+cb)+de);
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vec3 pd = (c*(ax+vec3(0.022,0.004,-0.10543))+df);
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// collapse color channels
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float pr = dot(saturate(pn/pd),vec3(0.45,0.45,0.45));
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// vignette
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float pv = saturate(pow(1.0 - dot(uv-.5, uv-.5), -.758) + -.23);
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float x = lerp(pr,pr*pr*pr,pv); // done
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return vec3(x,x,x);
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}
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out vec4 color;
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void main(void) {
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vec2 uv = TEXCOORD.st;
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vec4 src = texture2D(iChannel0, uv);
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color = vec4( PostFilmic_IlfordFp4Push(src.xyz, uv), src.a);
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}
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