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(svn r11076) -Fix: MakeTransparent of 32bpp blitter used 0..100; using 0..255 makes it much faster (frosch)

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-Fix: ComposeColourXXX could work a tiny bit faster when using 256, not 255 as value to divide with; downside is that it can give alpha errors (frosch)
This commit is contained in:
truelight
2007-09-09 21:56:52 +00:00
parent 38ff181ebf
commit 89bdfaacd9
3 changed files with 23 additions and 15 deletions
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30
src/blitter/32bpp_base.hpp
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@@ -48,15 +48,19 @@ public:
*/
static inline uint ComposeColourRGBA(uint r, uint g, uint b, uint a, uint current)
{
if (a == 0) return current;
if (a >= 255) return ComposeColour(0xFF, r, g, b);
uint cr, cg, cb;
cr = GB(current, 16, 8);
cg = GB(current, 8, 8);
cb = GB(current, 0, 8);
/* The 256 is wrong, it should be 255, but 256 is much faster... */
return ComposeColour(0xFF,
(r * a + cr * (255 - a)) / 255,
(g * a + cg * (255 - a)) / 255,
(b * a + cb * (255 - a)) / 255);
(r * a + cr * (256 - a)) / 256,
(g * a + cg * (256 - a)) / 256,
(b * a + cb * (256 - a)) / 256);
}
/**
@@ -64,24 +68,28 @@ public:
*/
static inline uint ComposeColourPA(uint colour, uint a, uint current)
{
if (a == 0) return current;
if (a >= 255) return (colour | 0xFF000000);
uint r, g, b, cr, cg, cb;
r = GB(colour, 16, 8);
g = GB(colour, 8, 8);
b = GB(colour, 0, 8);
r = GB(colour, 16, 8);
g = GB(colour, 8, 8);
b = GB(colour, 0, 8);
cr = GB(current, 16, 8);
cg = GB(current, 8, 8);
cb = GB(current, 0, 8);
/* The 256 is wrong, it should be 255, but 256 is much faster... */
return ComposeColour(0xFF,
(r * a + cr * (255 - a)) / 255,
(g * a + cg * (255 - a)) / 255,
(b * a + cb * (255 - a)) / 255);
(r * a + cr * (256 - a)) / 256,
(g * a + cg * (256 - a)) / 256,
(b * a + cb * (256 - a)) / 256);
}
/**
* Make a pixel looks like it is transparent.
* @param colour the colour already on the screen.
* @param amount the amount of transparency, times 100.
* @param amount the amount of transparency, times 256.
* @return the new colour for the screen.
*/
static inline uint MakeTransparent(uint colour, uint amount)
@@ -91,7 +99,7 @@ public:
g = GB(colour, 8, 8);
b = GB(colour, 0, 8);
return ComposeColour(0xFF, r * amount / 100, g * amount / 100, b * amount / 100);
return ComposeColour(0xFF, r * amount / 256, g * amount / 256, b * amount / 256);
}
/**