Algorithm to create a "scruffy" paper effect for UML Diagrams ?

Question

I like the scruffy paper effect of http://yuml.me UML diagrams, is there an algorithm for that preferably not in Ruby but in PHP, java or C#, I would like to see if It's easy to do the same thing in Rebol:

http://reboltutorial.com/blog/easy-yuml-dialect-for-mere-mortals2/