remove chroma decoding

gopro_8:7/unfish_gopro_8:7.glsl

@@ -78,39 +78,30 @@ const float luminance_min   =  16.0 / 255.0;
 const float luminance_max   = 235.0 / 255.0;
 const float luminance_range = luminance_max - luminance_min;
 
-const vec2 chroma_min    = vec2( 16.0 / 255.0);
-const vec2 chroma_max    = vec2(240.0 / 255.0);
-const vec2 chroma_range  = chroma_max - chroma_min;
-const vec2 chroma_center = vec2(0.5, 0.5);
-
-const vec3 yuv_min    = vec3(luminance_min,   chroma_min);
-const vec3 yuv_range  = vec3(luminance_range, chroma_range);
-const vec3 yuv_center = vec3(0.0, chroma_center);
-
 float decode_luminance(const in float x) {
     float y = (x - luminance_min) / luminance_range;
     return (y < 0.081) ? (y / 4.5) : pow((y + 0.099) / 1.099, 1.0 / 0.45);
 }
 
-vec2 decode_chroma(const in vec2 yz) {
-    return (yz - chroma_min) / chroma_range - chroma_center;
+float encode_luminance(const in float l) {
+    float x = (l < 0.018) ? (l * 4.5) : (pow(l, 0.45) * 1.099 - 0.099);
+    return x * luminance_range + luminance_min;
 }
 
-vec3 decode_pixel(const in vec3 pixel) {
-    return vec3(decode_luminance(pixel.x), decode_chroma(pixel.yz));
+vec3 decode_ycbcr(const in vec3 pixel) {
+    return vec3(decode_luminance(pixel.x), pixel.yz);
 }
 
-vec3 encode_color(const in vec3 color) {
-    float y = (color.x < 0.018) ? (color.x * 4.5) : (pow(color.x, 0.45) * 1.099 - 0.099);
-    return (vec3(y, color.yz) + yuv_center) * yuv_range + yuv_min;
+vec3 encode_ycbcr(const in vec3 color) {
+    return vec3(encode_luminance(color.x), color.yz);
 }
 
 #else
 
 #define decode_luminance(_x) (_x)
-#define decode_chroma(_yz)   (_yz)
-#define decode_pixel(_pixel) (_pixel)
-#define encode_color(_color) (_color)
+#define encode_luminance(_l) (_l)
+#define decode_ycbcr(_pixel) (_pixel)
+#define encode_ycbcr(_color) (_color)
 
 #endif
 
@@ -125,46 +116,27 @@ const vec2 corner_b = vec2(1.0, 0.0) + half_pixel;
 const vec2 corner_c = vec2(0.0, 1.0) + half_pixel;
 const vec2 corner_d = vec2(1.0, 1.0) + half_pixel;
 
-vec2 bilinear_params(const in vec2 coord, out vec2 a, out vec2 b, out vec2 c, out vec2 d) {
-    vec2 i, f = modf(coord - half_pixel, i);
-    a = i + corner_a;
-    b = i + corner_b;
-    c = i + corner_c;
-    d = i + corner_d;
-    return f;
-}
-
 vec3 texture_filter(const in vec2 y_coord) {
-    vec2 a, b, c, d, f = bilinear_params(y_coord, a, b, c, d);
+    vec2 i, f = modf(y_coord - half_pixel, i);
     float luminance = mix(
         mix(
-            decode_luminance(texture2DRect(myTextureY, a).x),
-            decode_luminance(texture2DRect(myTextureY, b).x),
+            decode_luminance(texture2DRect(myTextureY, i + corner_a).x),
+            decode_luminance(texture2DRect(myTextureY, i + corner_b).x),
             f.x),
         mix(
-            decode_luminance(texture2DRect(myTextureY, c).x),
-            decode_luminance(texture2DRect(myTextureY, d).x),
+            decode_luminance(texture2DRect(myTextureY, i + corner_c).x),
+            decode_luminance(texture2DRect(myTextureY, i + corner_d).x),
             f.x),
         f.y);
-    f = bilinear_params(y_coord * 0.5, a, b, c, d);
-    vec2 chroma = mix(
-        mix(
-            decode_chroma(vec2(texture2DRect(myTextureU, a).x, texture2DRect(myTextureV, a).x)),
-            decode_chroma(vec2(texture2DRect(myTextureU, b).x, texture2DRect(myTextureV, b).x)),
-            f.x),
-        mix(
-            decode_chroma(vec2(texture2DRect(myTextureU, c).x, texture2DRect(myTextureV, c).x)),
-            decode_chroma(vec2(texture2DRect(myTextureU, d).x, texture2DRect(myTextureV, d).x)),
-            f.x),
-        f.y);
-    return vec3(luminance, chroma);
+    vec2 uv_coord = y_coord * 0.5;
+    return vec3(luminance, texture2DRect(myTextureU, uv_coord).x, texture2DRect(myTextureV, uv_coord).x);
 }
 
 #else
 
 vec3 texture_filter(const in vec2 y_coord) {
     vec2 uv_coord = y_coord * 0.5;
-    return decode_pixel(vec3(
+    return decode_ycbcr(vec3(
         texture2DRect(myTextureY, y_coord).x,
         texture2DRect(myTextureU, uv_coord).x,
         texture2DRect(myTextureV, uv_coord).x));
@@ -196,5 +168,5 @@ void main() {
             color += texture_sample(coord + offset);
         }
     }
-    gl_FragColor = vec4(encode_color(color * subsampling_scale), 1.0);
+    gl_FragColor = vec4(encode_ycbcr(color * subsampling_scale), 1.0);
 }