Changed max. avatar dimensions, resize existing avatars?

[Marco]

I recently changed the max. avatar size on my forums. Previously, the limit was set at 600x600 and the images were only downsized in the IMG-tag. Ugly, I know, but now we have quite a few people with really huge avatars. Changing them all manually is not an option, so I imagine we'll need some sort of script to do it for us. Has anyone ever written anything like that? I imagine you'd have the script look at every avatar, check the dimensions and resize if necessary. It sounds simple, but how would one go about doing it?