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AGS: Fix broken calendar puzzle in Lamplight City

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This commit is contained in:
Paul Gilbert 2021-08-14 19:45:59 -07:00
parent 29c5f6e749
commit 49a5fd6ebe
1 changed files with 17 additions and 12 deletions
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29
engines/ags/lib/allegro/surface.h
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@ -134,18 +134,23 @@ public:
inline void rgbBlend(uint8 rSrc, uint8 gSrc, uint8 bSrc, uint8 &rDest, uint8 &gDest, uint8 &bDest, uint32 alpha) const {
// Original logic has uint32 src and dst colors as RGB888
// if (alpha)
// ++alpha;
// uint32 res = ((src & 0xFF00FF) - (dst & 0xFF00FF)) * alpha / 256 + dst;
// dst &= 0x00FF00;
// src &= 0x00FF00;
// uint32 g = (src - dst) * alpha / 256 + dst;
// return (res & 0xFF00FF) | (g & 0x00FF00)
double sAlpha = (double)(alpha & 0xff) / 255.0;
rDest = static_cast<uint8>(rSrc * sAlpha + rDest * (1. - sAlpha));
gDest = static_cast<uint8>(gSrc * sAlpha + gDest * (1. - sAlpha));
bDest = static_cast<uint8>(bSrc * sAlpha + bDest * (1. - sAlpha));
// Note: the original's handling varies slightly for R & B vs G.
// We need to exactly replicate it to ensure Lamplight City's
// calendar puzzle works correctly
if (alpha)
alpha++;
uint32 x = ((uint32)rSrc << 16) | ((uint32)gSrc << 8) | (uint32)bSrc;
uint32 y = ((uint32)rDest << 16) | ((uint32)gDest << 8) | (uint32)bDest;
uint32 res = ((x & 0xFF00FF) - (y & 0xFF00FF)) * alpha / 256 + y;
y &= 0xFF00;
x &= 0xFF00;
uint32 g = (x - y) * alpha / 256 + y;
rDest = (res >> 16) & 0xff;
gDest = (g >> 8) & 0xff;
bDest = res & 0xff;
}
inline void argbBlend(uint32 aSrc, uint8 rSrc, uint8 gSrc, uint8 bSrc, uint8 &aDest, uint8 &rDest, uint8 &gDest, uint8 &bDest) const {