Renaming Images to the actual file size

I have 200 image files that need to be renamed to their actual photo size. For example, an image is named [login to view URL], with the size of 160x600. You would rename this image 160x600_1.jpg. Then the next image of 160x600 would be renamed to [login to view URL], then [login to view URL] and so forth. There are many different sizes, and a total of 200 images. This is a very simple project a kid could do, so the lowest bidder will probably win this. I need this done AS SOON AS POSSIBLE!