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emu/rendlay.cpp: Fix accumulation error causing black pixels on certain transparent colours.

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This commit is contained in:
Vas Crabb 2020-10-14 04:55:09 +11:00
parent d6a860dfd7
commit 54a45a29ea
1 changed files with 16 additions and 14 deletions
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30
src/emu/rendlay.cpp
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@ -1969,9 +1969,9 @@ protected:
{
// compute premultiplied colors
u32 const a(c.a * 255.0F);
u32 const r(c.r * c.a * (255.0F * 255.0F * 255.0F));
u32 const g(c.g * c.a * (255.0F * 255.0F * 255.0F));
u32 const b(c.b * c.a * (255.0F * 255.0F * 255.0F));
u32 const r(u32(c.r * (255.0F * 255.0F)) * a);
u32 const g(u32(c.g * (255.0F * 255.0F)) * a);
u32 const b(u32(c.b * (255.0F * 255.0F)) * a);
u32 const inva(255 - a);
// we're translucent, add in the destination pixel contribution
@ -1981,10 +1981,11 @@ protected:
for (u32 x = bounds.left(); x <= bounds.right(); ++x, ++dst)
{
rgb_t const dpix(*dst);
u32 const finala((a * 255) + (dpix.a() * inva));
u32 const finalr(r + (dpix.r() * dpix.a() * inva));
u32 const finalg(g + (dpix.g() * dpix.a() * inva));
u32 const finalb(b + (dpix.b() * dpix.a() * inva));
u32 const da(dpix.a());
u32 const finala((a * 255) + (da * inva));
u32 const finalr(r + (u32(dpix.r()) * da * inva));
u32 const finalg(g + (u32(dpix.g()) * da * inva));
u32 const finalb(b + (u32(dpix.b()) * da * inva));
// store the target pixel, dividing the RGBA values by the overall scale factor
*dst = rgb_t(finala / 255, finalr / finala, finalg / finala, finalb / finala);
@ -2260,9 +2261,9 @@ private:
u32 const a(c.a * fill * 255.0F);
if (a)
{
u32 const r(c.r * c.a * fill * (255.0F * 255.0F * 255.0F));
u32 const g(c.g * c.a * fill * (255.0F * 255.0F * 255.0F));
u32 const b(c.b * c.a * fill * (255.0F * 255.0F * 255.0F));
u32 const r(u32(c.r * (255.0F * 255.0F)) * a);
u32 const g(u32(c.g * (255.0F * 255.0F)) * a);
u32 const b(u32(c.b * (255.0F * 255.0F)) * a);
alpha_blend(dest, a, r, g, b, 255 - a);
}
}
@ -2270,10 +2271,11 @@ private:
void alpha_blend(u32 &dest, u32 a, u32 r, u32 g, u32 b, u32 inva)
{
rgb_t const dpix(dest);
u32 const finala((a * 255) + (dpix.a() * inva));
u32 const finalr(r + (dpix.r() * dpix.a() * inva));
u32 const finalg(g + (dpix.g() * dpix.a() * inva));
u32 const finalb(b + (dpix.b() * dpix.a() * inva));
u32 const da(dpix.a());
u32 const finala((a * 255) + (da * inva));
u32 const finalr(r + (u32(dpix.r()) * da * inva));
u32 const finalg(g + (u32(dpix.g()) * da * inva));
u32 const finalb(b + (u32(dpix.b()) * da * inva));
dest = rgb_t(finala / 255, finalr / finala, finalg / finala, finalb / finala);
}