A system for enabling user interaction is disclosed. The system includes a printer for printing print data on a form. The print data is indicative of a plurality of marks. Each mark has a predetermined pattern common to all marks and coded data. The predetermined pattern includes a rotationally invariant...http://www.google.de/patents/US8068250?utm_source=gb-gplus-sharePatent US8068250 - System for allowing handwritten interaction with a computer
