[SDL] Create a transparent surface?

[Markus Laire]

On 6/7/07, L-28C <kixdemp at gmail.com> wrote:
> Hello everyone!
>
> I was wondering how to create a transparent surface (alpha 0).
> SDL_CreateRGBSurface fills it black, but I'm blitting tiles to this
> surface, and whenever I blit that to the screen the black background
> shows up...
>
> Anyonw know how to do this? Thanks!
>
> (Can't use color keys because my tiles have black in them... maybe I can
> fill it with, say, magenta?)

This should fill the surface with transparent pixels:

SDL_FillRect(surface, NULL, SDL_MapRGBA(surface->format, 0, 0, 0, 0));

http://www.libsdl.org/cgi/docwiki.cgi/SDL_5fFillRect says: "If the
color value contains an alpha value then the destination is simply
"filled" with that alpha information, no blending takes place."

-- 
Markus Laire