Possible? ID "blank" spaces in image

We need to emulate the "Copyspace" function from Istockphoto.com. For a quick reference, please see: http://www.istockphoto.com/file_search.php?action=file&text=woman

and then click 'Advanced Search'. On the bottom right is the Copyspace interface. Basically, they have scanned the images into 3 x 3 squares, organized by empty space. So, if people need a picture that is "blank" (not necessarily white, just a generally empty area of any color) on the left side, then they can select the 3 left squares.

I know Graphics Mill is pretty powerful.. is this possible to accomplish? It will literally seal the deal for purchase if we can have a quick and dirty example of how to implement this.

Thanks