Is it possible to check a returned imagelink for validity?

I'm creating some tests for an ad server, and I want to test the validity / correctness of the returned ads.

For this I would (from an assertion script) like to get the image link, and then retrieve the image and do some checks (width/height/format/does it exist, etc)

Has someone done this before?

I'm able to parse the link from the response, but am stuck on how to actually get the image.