SDL_DisplayFormat (3) - Linux Manuals
SDL_DisplayFormat: Convert a surface to the display format
NAMESDL_DisplayFormat - Convert a surface to the display format
This function takes a surface and copies it to a new surface of the pixel format and colors of the video framebuffer, suitable for fast blitting onto the display surface. It calls SDL_ConvertSurface
If you want to take advantage of hardware colorkey or alpha blit acceleration, you should set the colorkey and alpha value before calling this function.
SDL_ConvertSurface, SDL_DisplayFormatAlpha SDL_SetAlpha, SDL_SetColorKey, SDL_Surface