pandory500/SDL-mirror
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Fixed bitmap order interpretation; SDL defaults to MSB ordering so a bitstream corresponds to a pixel stream.

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The bitmap ordering is defined such that the numbering refers to the pixel index from left to right, and the number position refers to the bit position in the byte.

SDL_BITMAPORDER_4321 is the fourth pixel at the high bit and the first pixel at the low bit (LSBFirst)

SDL_BITMAPORDER_1234 is the first pixel at the high bit and the fourth pixel at the low bit (MSBFirst)
This commit is contained in:
Sam Lantinga 2011-03-07 00:30:05 -08:00
parent 2bea0e636f
commit e43f8d8003
3 changed files with 10 additions and 45 deletions
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10
include/SDL_pixels.h
View file

@ -149,16 +149,16 @@ enum
{ {
SDL_PIXELFORMAT_UNKNOWN, SDL_PIXELFORMAT_UNKNOWN,
SDL_PIXELFORMAT_INDEX1LSB = SDL_PIXELFORMAT_INDEX1LSB =
SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX1, SDL_BITMAPORDER_1234, 0,
1, 0),
SDL_PIXELFORMAT_INDEX1MSB =
SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX1, SDL_BITMAPORDER_4321, 0, SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX1, SDL_BITMAPORDER_4321, 0,
1, 0), 1, 0),
SDL_PIXELFORMAT_INDEX1MSB =
SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX1, SDL_BITMAPORDER_1234, 0,
1, 0),
SDL_PIXELFORMAT_INDEX4LSB = SDL_PIXELFORMAT_INDEX4LSB =
SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX4, SDL_BITMAPORDER_1234, 0, SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX4, SDL_BITMAPORDER_4321, 0,
4, 0), 4, 0),
SDL_PIXELFORMAT_INDEX4MSB = SDL_PIXELFORMAT_INDEX4MSB =
SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX4, SDL_BITMAPORDER_4321, 0, SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX4, SDL_BITMAPORDER_1234, 0,
4, 0), 4, 0),
SDL_PIXELFORMAT_INDEX8 = SDL_PIXELFORMAT_INDEX8 =
SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX8, 0, 0, 8, 1), SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_INDEX8, 0, 0, 8, 1),

6
src/video/SDL_pixels.c
View file

@ -242,9 +242,11 @@ SDL_MasksToPixelFormatEnum(int bpp, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask,
{ {
switch (bpp) { switch (bpp) {
case 1: case 1:
/* SDL defaults to MSB ordering */
return SDL_PIXELFORMAT_INDEX1MSB;
case 4: case 4:
/* Can't tell if this is LSB or MSB bitmap ordering... */ /* SDL defaults to MSB ordering */
break; return SDL_PIXELFORMAT_INDEX4MSB;
case 8: case 8:
if (Rmask == 0) { if (Rmask == 0) {
return SDL_PIXELFORMAT_INDEX8; return SDL_PIXELFORMAT_INDEX8;

39
src/video/SDL_surface.c
View file

@ -75,44 +75,7 @@ SDL_CreateRGBSurface(Uint32 flags,
SDL_FreeSurface(surface); SDL_FreeSurface(surface);
return NULL; return NULL;
} }
if (Rmask || Bmask || Gmask) { if (palette->ncolors == 2) {
const SDL_PixelFormat *format = surface->format;
/* create palette according to masks */
int i;
int Rm = 0, Gm = 0, Bm = 0;
int Rw = 0, Gw = 0, Bw = 0;
if (Rmask) {
Rw = 8 - format->Rloss;
for (i = format->Rloss; i > 0; i -= Rw)
Rm |= 1 << i;
}
if (Gmask) {
Gw = 8 - format->Gloss;
for (i = format->Gloss; i > 0; i -= Gw)
Gm |= 1 << i;
}
if (Bmask) {
Bw = 8 - format->Bloss;
for (i = format->Bloss; i > 0; i -= Bw)
Bm |= 1 << i;
}
for (i = 0; i < palette->ncolors; ++i) {
int r, g, b;
r = (i & Rmask) >> format->Rshift;
r = (r << format->Rloss) | ((r * Rm) >> Rw);
palette->colors[i].r = r;
g = (i & Gmask) >> format->Gshift;
g = (g << format->Gloss) | ((g * Gm) >> Gw);
palette->colors[i].g = g;
b = (i & Bmask) >> format->Bshift;
b = (b << format->Bloss) | ((b * Bm) >> Bw);
palette->colors[i].b = b;
}
} else if (palette->ncolors == 2) {
/* Create a black and white bitmap palette */ /* Create a black and white bitmap palette */
palette->colors[0].r = 0xFF; palette->colors[0].r = 0xFF;
palette->colors[0].g = 0xFF; palette->colors[0].g = 0xFF;