Image Field Sampler with diagrid pattern

I am trying to use the image sampler with a diagrid pattern in which the diagrid changes based on the image. I know how to do this with circles, but would like to know what changes should be made to have this react to a diagrid. Here is an example of what i am going for.

http://madeincalifornia.blogspot.com/2009/08/image-field02.html