Re: [pygame] ARGB vs. RGBA

["Brian Fisher" <brian@xxxxxxxxxxxxxxxxxxx>]

On 12/16/06, Jakub Piotr Cłapa <jpc@xxxxxxxxxxxxx> wrote:
> It just that I don't understand why ARGB isn't just ARGB in memory (1
> byte A, 1 byte R, 1 byte G and 1 byte B). Look at lines 627 and 629 in
> src/image.c:
> #v+
> #if SDL_BYTEORDER == SDL_LIL_ENDIAN
>                                          0xFF<<24, 0xFF, 0xFF<<8, 0xFF<<16);
> #else
>                                          0xFF, 0xFF<<24, 0xFF<<16, 0xFF<<8);
> #endif
> #v-
> The BIG_ENDIAN part should be 0xFF<<16, 0xFF<<8, 0xFF, 0xFF<<24; the
> same as LIL just in reverse order.
Hmmm.. they both look wrong to me... they look like GBAR

I would think lil endian would be this:
RMask = 0xFF<<8, GMask = 0xFF<<16, BMask = 0xFF<<24, AMask = 0xFF

and big endian would be:
RMask = 0xFF<<16, GMask = 0xFF<<8, BMask = 0xFF, AMask = 0xFF<<24

so I think you are right about what the big-endian mask should be, but
it's not true that you just swap the argument order for big to little
endian - what you really do is swap the shifts (so shift 24 becomes
shift 0, 16 becomes 8, 8 becomes 16 and 0 becomes 24)

--

so jakub, do you have code for a cairo/pygame sample that tests this?