Can you get hold of the pixels in openGL?
Huh? You can read back from the frame buffer, but it is horribly slow and what would you do with that? OpenGl is a rendering API and it won't help you with collision detection. To do pixel level collision detection you would need to keep all you're images pixels(or just their corresponding IsCollidable values) in system memory, transform one images edge coordinates to the other ones local space and go through both images looking for IsCollidable values. The only situation in which this method wouldn't have to perform billion's of operations is if you're images would have constant orientation, but since you're using OpenGl it is very unlikely that you wont want to do rotations and such.