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render/vulkan: unify alpha pre-multiplication in output shader

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Instead of handling alpha pre-multiplication in each branch, add
some common logic before and after handling OUTPUT_TRANSFORM.
This commit is contained in:
Simon Ser 2025-02-23 15:39:10 +01:00
parent c9d6339b60
commit e83b06e732
1 changed files with 18 additions and 21 deletions
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39
render/vulkan/shaders/output.frag
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@ -23,38 +23,35 @@ float linear_channel_to_srgb(float x) {
return max(min(x * 12.92, 0.04045), 1.055 * pow(x, 1. / 2.4) - 0.055);
}
vec4 linear_color_to_srgb(vec4 color) {
if (color.a == 0) {
return vec4(0);
}
color.rgb /= color.a;
color.rgb = vec3(
vec3 linear_color_to_srgb(vec3 color) {
return vec3(
linear_channel_to_srgb(color.r),
linear_channel_to_srgb(color.g),
linear_channel_to_srgb(color.b)
);
color.rgb *= color.a;
return color;
}
void main() {
vec4 val = subpassLoad(in_color).rgba;
if (OUTPUT_TRANSFORM == OUTPUT_TRANSFORM_LUT_3D) {
if (val.a == 0) {
out_color = vec4(0);
return;
}
// Convert from pre-multiplied alpha to straight alpha
vec3 rgb = val.rgb / val.a;
vec4 in_color = subpassLoad(in_color).rgba;
// Convert from pre-multiplied alpha to straight alpha
float alpha = in_color.a;
vec3 rgb;
if (alpha == 0) {
rgb = vec3(0);
} else {
rgb = in_color.rgb / alpha;
}
if (OUTPUT_TRANSFORM == OUTPUT_TRANSFORM_LUT_3D) {
// Apply 3D LUT
vec3 pos = data.lut_3d_offset + rgb * data.lut_3d_scale;
rgb = texture(lut_3d, pos).rgb;
} else { // OUTPUT_TRANSFORM_INVERSE_SRGB
// Produce sRGB encoded values
rgb = linear_color_to_srgb(rgb);
}
// Back to pre-multiplied alpha
out_color = vec4(rgb * val.a, val.a);
} else { // OUTPUT_TRANSFORM_INVERSE_SRGB
// Produce post-premultiplied sRGB encoded values
out_color = linear_color_to_srgb(val);
}
out_color = vec4(rgb * alpha, alpha);
}