Convert IMG tag to URL tag if linked image is over a certain KB size

[AusPhotography]

I have done a bit of hunting and cannot find a relevant product.

I have a photography forum and members are linking in photos, sometimes with ridiculously large filesizes (KB). What I am looking for is a way to check the KB filesize of a linked photo and if it is over a pre-determined size, replace the IMG tag with a URL tag so that it displays as a link rather than display the actual photo.

Thanks in advance.