Does anyone know of a good fast algorithm to emulate the 8bit palette shifts
on a 16bit surface? I could replace each pixel manually but that goes very
slow…
Maybe i should try that in ASM?
If anyone knows of a better algorithm, please let me know… ty_________________________________________________________________
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Does anyone know of a good fast algorithm to emulate the 8bit palette shifts
on a 16bit surface? I could replace each pixel manually but that goes very
slow…
My 2 cents, can’t you use an 8 bit surface for the portion you want to use the colorcycle (palette shift) and convert it to 16 bits, blitting it over the portion you want it to be?
Paulo
Does anyone know of a good fast algorithm to emulate
the 8bit palette shifts
on a 16bit surface? I could replace each pixel
manually but that goes very
slow…Maybe i should try that in ASM?
I’m a little confused here… mainly due to the lack
of setup information (as 16 bit surfaces = RGB, not
palette).
If you have a source palettized image and a
corresponding 16 bit rgb surface for rendering, I’d do
something like the bellow (note: this only updates
changes in palette… if the source is animated, a
seperate algorythm will be needed for that).
void update (
SDL_Surface *src, //assumed 8 bits in example
SDL_Surface *dest, //assumed 16 bits
UInt8 palc_min,
UInt8 palc_max, //the minimum and maximum range of
palette changes… used to speed up destination
update.
UInt16 *palette //Palette pre-converted into 16 bit
format (points to array…very much optimizable!)
) {
assert( src->w == dest->w );
assert( src->h == dest->h );
if (SDL_MUSTLOCK(src)) SDL_LockSurface(src);
if (SDL_MUSTLOCK(dest)) SDL_LockSurface(dest);
UInt8 *src_pixel = (UInt8 *)src->pixels;
UInt16 *dest_pixel = (UInt16 *)dest->pixels;
unsigned int i = src->w * src->h;
while (i–)
{
if ((*src_pixel >= palc_min) && (*src_pixel <=
palc_max))
*dest_pixel = palette[*src_pixel];
dest_pixel++;
src_pixel++;
}
if (SDL_MUSTLOCK(src)) SDL_UnlockSurface(src);
if (SDL_MUSTLOCK(dest)) SDL_UnlockSurface(dest);
}
possible optimizations: maybe in asm (hopefully the
optimizer will do it), but if allways updating all the
(possibly) animated palletes, make them pushed all to
the back end and eliminate the palc_max parts (aka lay
out the palette so that, say, 0-200 are non animated,
and 201-255 are). This saves a comparison per pixel.
Hope some of that helps.
-Mike__________________________________
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