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Fixed SDL_DisplayFormatAlpha() on RGB surfaces with alpha

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--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40432
This commit is contained in:
Sam Lantinga 2002-08-01 23:06:39 +00:00
parent 8613885333
commit a9c0bef803
4 changed files with 63 additions and 6 deletions
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62
src/video/SDL_surface.c
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@ -211,6 +211,7 @@ int SDL_SetColorKey (SDL_Surface *surface, Uint32 flag, Uint32 key)
SDL_InvalidateMap(surface->map);
return(0);
}
/* This function sets the alpha channel of a surface */
int SDL_SetAlpha (SDL_Surface *surface, Uint32 flag, Uint8 value)
{
Uint32 oldflags = surface->flags;
@ -269,6 +270,52 @@ int SDL_SetAlpha (SDL_Surface *surface, Uint32 flag, Uint8 value)
SDL_InvalidateMap(surface->map);
return(0);
}
int SDL_SetAlphaChannel(SDL_Surface *surface, Uint8 value)
{
int row, col;
int offset;
Uint8 *buf;
if ( (surface->format->Amask != 0xFF000000) &&
(surface->format->Amask != 0x000000FF) ) {
SDL_SetError("Unsupported surface alpha mask format");
return -1;
}
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
if ( surface->format->Amask == 0xFF000000 ) {
offset = 3;
} else {
offset = 0;
}
#else
if ( surface->format->Amask == 0xFF000000 ) {
offset = 0;
} else {
offset = 3;
}
#endif /* Byte ordering */
/* Quickly set the alpha channel of an RGBA or ARGB surface */
if ( SDL_MUSTLOCK(surface) ) {
if ( SDL_LockSurface(surface) < 0 ) {
return -1;
}
}
row = surface->h;
while (row--) {
col = surface->w;
buf = (Uint8 *)surface->pixels + row * surface->pitch + offset;
while(col--) {
*buf = value;
buf += 4;
}
}
if ( SDL_MUSTLOCK(surface) ) {
SDL_UnlockSurface(surface);
}
return 0;
}
/*
* A function to calculate the intersection of two rectangles:
@ -748,8 +795,13 @@ SDL_Surface * SDL_ConvertSurface (SDL_Surface *surface,
}
}
if ( (surface_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
alpha = surface->format->alpha;
SDL_SetAlpha(surface, 0, 0);
/* Copy over the alpha channel to RGBA if requested */
if ( format->Amask ) {
surface->flags &= ~SDL_SRCALPHA;
} else {
alpha = surface->format->alpha;
SDL_SetAlpha(surface, 0, 0);
}
}
/* Copy over the image data */
@ -780,7 +832,11 @@ SDL_Surface * SDL_ConvertSurface (SDL_Surface *surface,
SDL_SetAlpha(convert, aflags|(flags&SDL_RLEACCELOK),
alpha);
}
SDL_SetAlpha(surface, aflags, alpha);
if ( format->Amask ) {
surface->flags |= SDL_SRCALPHA;
} else {
SDL_SetAlpha(surface, aflags, alpha);
}
}
/* We're ready to go! */