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TexCache: Correct DXT5 alpha calculation.

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This matches PSP alpha values from an exhaustive test.
This commit is contained in:
Unknown W. Brackets 2021-09-12 09:35:53 -07:00
parent db21d0e7fc
commit 1ee5352d3e
1 changed files with 7 additions and 9 deletions
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16
GPU/Common/TextureDecoder.cpp
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@ -375,20 +375,19 @@ void DXTDecoder::DecodeColors(const DXT1Block *src, bool ignore1bitAlpha) {
}
static inline u8 lerp8(const DXT5Block *src, int n) {
// These weights translate alpha1/alpha2 to fixed 8.8 point, pre-divided by 7.
int weight1 = ((7 - n) << 8) / 7;
int weight2 = (n << 8) / 7;
return (u8)((src->alpha1 * weight1 + src->alpha2 * weight2 + 255) >> 8);
// These weights multiple alpha1/alpha2 to fixed 8.8 point.
int alpha1 = (src->alpha1 * ((7 - n) << 8)) / 7;
int alpha2 = (src->alpha2 * (n << 8)) / 7;
return (u8)((alpha1 + alpha2 + 31) >> 8);
}
static inline u8 lerp6(const DXT5Block *src, int n) {
int weight1 = ((5 - n) << 8) / 5;
int weight2 = (n << 8) / 5;
return (u8)((src->alpha1 * weight1 + src->alpha2 * weight2 + 255) >> 8);
int alpha1 = (src->alpha1 * ((5 - n) << 8)) / 5;
int alpha2 = (src->alpha2 * (n << 8)) / 5;
return (u8)((alpha1 + alpha2 + 31) >> 8);
}
void DXTDecoder::DecodeAlphaDXT5(const DXT5Block *src) {
// TODO: Check if alpha is still not 100% correct.
alpha_[0] = src->alpha1;
alpha_[1] = src->alpha2;
if (alpha_[0] > alpha_[1]) {
@ -460,7 +459,6 @@ void DecodeDXT3Block(u32 *dst, const DXT3Block *src, int pitch, int height) {
dxt.WriteColorsDXT3(dst, src, pitch, height);
}
// The alpha channel is not 100% correct
void DecodeDXT5Block(u32 *dst, const DXT5Block *src, int pitch, int height) {
DXTDecoder dxt;
dxt.DecodeColors(&src->color, true);