I'm making a sprite sheet loader, and so far it's going perfectly, except for one slight problem: When you call the function GetSprite(int index), the function identifies the part of the sprite sheet at index, and grabs it to return to the user. My method is to create a new surface with SDL_CreateRGBSurface, blit the portion of the sprite that I want onto it, and return it. Works fine. However, the new surface doesn't preserve the alpha of the original (Using PNG), and I suspect it's an issue with create RGB Surface. Have a look at my code:

SDL_Surface *sprite = SDL_CreateRGBSurface(SDL_SWSURFACE, width, height, 32, 0, 0, 0, 0);

int code = SDL_BlitSurface(spritesheet, &srcrect, sprite, NULL); // blit the section we want into "sprite"

if(code == 0)
{
	return sprite; // it's up to the programmer to free the surface.
}
else
{
	printf("Unable to blit sprite\n");
	return NULL;
}

The function does what it's supposed to, but when displayed, the image is black where there would normally be alpha transparency. What can I do to fix it?

I never liked using preprocessor stuff within my code, but trying that, it makes the whole image white. I remember using that code before in some really old project, and it worked fine...

Changing the code to

SDL_Surface *sprite = SDL_CreateRGBSurface(SDL_SWSURFACE, width, height, 32, rmask, gmask, bmask, amask);SDL_Surface *sprite2 = SDL_DisplayFormatAlpha(sprite);SDL_FreeSurface(sprite);// etc, then return sprite2

makes the images white, as does just using the straight RGB surface and not formatting it. However, using DisplayFormat instead of DisplayFormatAlpha brings it back to the original black.

I would say "Is it possible that I'm doing something wrong", but I already know that I'm doing something wrong. Something stupid. This code has worked before, and I can't figure out why it doesn't want to work now

Edit: I'm under the impression that SetColorKey won't work for the surfaces in question, since it only sets 1 color as being a certain level of transparency, while a PNG image can have any number of colors transparent, and all different levels of transparency

Well, I gotta head out, but thanks anyway