[SDL] aalineRGBA problem

[clemens kirchgatterer]

> > I suggest you skip the alpha stuff unless you need it and use
> > SDL_DisplayFormat to get an image suitable for blitting.
> > You're using ABGR, which on little endian machines happens to be what
> > the opengl wants (big endiand RGBA), but using that to blit
> > on screen in 2D is probably not what you're looking for, because I'm
> > betting you're display surface has something other than ABGR
> > (could it be ARGB?).
>
> Sorry ... I don't understand fully the concept behind these RGBA masks.

the RGBA mask defines where in a single pixelvalue the different color
channels get stored. this means, for example, if you are in a 32 bit mode,
one pixel is stored in a 32 bit integer and each color of RGBA use 8 bits.

pixel = 00101001 00101111 10101011 00011100

if the masks are set as follwing:

amask = 0xff000000
rmask = 0x000000ff
gmask = 0x0000ff00
bmask = 0x00ff0000

then the MSB holds the alpha value of the pixel and the LSB the red
colour channel. you get the idea?

hope this helps ...
clemens