scan image, create links from content (php hopeful

Question

I'm not sure if this could work, but I've got pictures of maps with #'s inside a little box on top of the map to show locations. See my image example:

I'm hoping to find a script to 'scan' the image and create links from the number locations (and overlay those links where the boxes are)

In the image example, all the boxes have a 3 in them, but on the other maps they may go from 1 to 400. So I'm hoping to be able to get a link overlay on the boxes sending to another image. Ie, map box #3 would create a link such as http://www.example.com/images/image3.jpg when hovered over. (as long as I can take the # in the box and stuff it in a link over the box.