Hi all,

I'm trying to create some OpenGL textures from SDL surfaces. So far, I can handle basic loading as well as a texture with colorkey (RGBA images only).

However, RGB images do not respond properly, i.e. the pixels which should be transparent are unchanged. I suspect that this is because the image needs an alpha channel, so I need to convert the image from an RGB surface to an RGBA surface, but I'm not sure how to do this.

I'll post my code if it helps, but basically I'm looping through all the pixels in the surface and setting any, that match the colorkey, to a fully transparent black pixel.

Hello NordCoder. I've experienced some trouble with (lack of) alpha channels. I solved it by opening the image in GIMP and then putting an alpha channel to it, then saving it back.

Don't know if it helps, maybe worth a try.

Never tried it coding with SDL.

Hi Leonardo!

Manually adding an alpha channel was suggested on some forums, but I would prefer to do it in code instead. It seems that SDL_SetColorKey(...) works on RGB surfaces so there must be some way to do it, possibly SDL_ConvertSurface(...) or SDL_CreateRGBSurface(...).

I'll try to see if those works and if not, then just do it in a image program

Thanks for your help!