Like most VB forums, my members can embed an image into their posts/blogs etc by using

tags, which is all well and good. However....
It is possible to embed images of any dimensions, so if they embed a large image this screws the format of the page and everything is misaligned and difficult to read.
So I would like to "mod" the img bbcode so that it will display the image at a max dimension of say 640x480, if the user clicks the image it opens (maybe in a lightbox etc) at full size.
Does anybody know of any mods that can do this?