How to Pull Images Dynamically from an External Page (similar to Digg.com)

When you go to submit links on Digg they've had a system setup that pulls thumbnails from the images on the page. On the old Digg v3 system it worked awesome. Digg v4 still has it, but it often grabs pointless images such as logos and banners.

However I'm looking to mimic this functionality on my own site. Could this be done solely with jQuery/JSON? If there is a backend required. ideally PHP would be e开发者_开发知识库asiest. But I'm open to suggestions. Honestly don't know where to start with this piece of code.