replace image if it is too small

is there any way to set up the feed so that if it pulls a tiny image from a feed it will use my default image? ie one of the feeds I’m pulling doesn’t have images, but feedzy is pulling the “email this” image at the bottom of their feed. It’s a tiny image and is rectangle, so when it pulls onto my site it’s distorted.

I would like to be able to say if the image is less than 5k use default image from that feed.

Is this possible? Can you point me to where I could look in the code if it isn’t already possible?