Using LUMINANCE with OpenGL 3.2 Core contex results in all images being
solid black (in the menu, world, and the console). In the end the whole
screen was solid black except the intro video.
Store images in RGB and RGBA instead. This doesn't affect r_grayscale
visually. If there is issues with it now possibly using compressed
formats, then it would already be an issue for r_grayscale 0.9.