I think I'll just make a basic assumption of the image being set to "scale to cover" and not "centered," "scale to fit" or "tiled." That's the most likely use case since I think it's the default setting for images that are "too big" or "too small" or at very least the best looking one. For the same size image vs monitor, it just does nothing so that's an easy case to check for too.
Statistics: Posted by Socks the Fox — Today, 2:54 am