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added consideration of alpha channels of original colors when blending

This commit is contained in:
bagomot 2023-05-15 12:18:54 +03:00
parent a04bbd8789
commit 4fd08b2b8f
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GPG Key ID: F28BBD3A259717A8
1 changed files with 10 additions and 4 deletions
src/dlangui/graphics
colors.d

14
src/dlangui/graphics/colors.d
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@ -190,20 +190,26 @@ uint makeRGBA(T)(T r, T g, T b, T a) pure nothrow {
/// blend two RGB pixels using alpha
uint blendARGB(uint dst, uint src, uint alpha) pure nothrow {
uint dstalpha = dst >> 24;
if (dstalpha > 0x80)
return src;
uint srca = (src >> 24) & 0xFF;
uint dsta = (dst >> 24) & 0xFF;
uint srcr = (src >> 16) & 0xFF;
uint srcg = (src >> 8) & 0xFF;
uint srcb = (src >> 0) & 0xFF;
uint dstr = (dst >> 16) & 0xFF;
uint dstg = (dst >> 8) & 0xFF;
uint dstb = (dst >> 0) & 0xFF;
uint ialpha = 255 - alpha;
uint r = ((srcr * ialpha + dstr * alpha) >> 8) & 0xFF;
uint g = ((srcg * ialpha + dstg * alpha) >> 8) & 0xFF;
uint b = ((srcb * ialpha + dstb * alpha) >> 8) & 0xFF;
return (r << 16) | (g << 8) | b;
uint a = ((srca * ialpha + dsta * alpha) >> 8) & 0xFF;
return (a << 24) | (r << 16) | (g << 8) | b;
}
//immutable int[3] COMPONENT_OFFSET_BGR = [2, 1, 0];