How to use the fimg tags?

[Warmmedown]

Does anybody know how to use the fimg tags to post an image with a custom size (in pixels)?

I assumed it would be:

[fimg=500x300]http://urlofimage.com[/fimg]

but that just ends up posting the link

 

[SSJ2]

Can’t say I’ve ever tried to use that function. Why not just resize your image and then post it normally?