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premultiply alpha before filtering

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Chad Brokaw 2023-03-10 02:04:21 -05:00
parent a8585781cd
commit d12b711fe1
1 changed files with 9 additions and 6 deletions
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15
shader/fine.wgsl
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@ -297,12 +297,11 @@ fn main(
if all(atlas_uv < atlas_extents) { if all(atlas_uv < atlas_extents) {
let uv_quad = vec4(max(floor(atlas_uv), image.atlas_offset), min(ceil(atlas_uv), atlas_extents)); let uv_quad = vec4(max(floor(atlas_uv), image.atlas_offset), min(ceil(atlas_uv), atlas_extents));
let uv_frac = fract(atlas_uv); let uv_frac = fract(atlas_uv);
let a = textureLoad(image_atlas, vec2<i32>(uv_quad.xy), 0); let a = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.xy), 0));
let b = textureLoad(image_atlas, vec2<i32>(uv_quad.xw), 0); let b = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.xw), 0));
let c = textureLoad(image_atlas, vec2<i32>(uv_quad.zy), 0); let c = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.zy), 0));
let d = textureLoad(image_atlas, vec2<i32>(uv_quad.zw), 0); let d = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.zw), 0));
let color = mix(mix(a, b, uv_frac.y), mix(c, d, uv_frac.y), uv_frac.x); let fg_rgba = mix(mix(a, b, uv_frac.y), mix(c, d, uv_frac.y), uv_frac.x);
let fg_rgba = vec4(color.rgb * color.a, color.a);
let fg_i = fg_rgba * area[i]; let fg_i = fg_rgba * area[i];
rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i; rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i;
} }
@ -370,3 +369,7 @@ fn main(
} }
#endif #endif
} }
fn premul_alpha(rgba: vec4<f32>) -> vec4<f32> {
return vec4(rgba.rgb * rgba.a, rgba.a);
}