Recognizing patterns when drawing over the iPhone screen

Question

I'm trying to write a game where the user can issue commands by drawing certain patterns with his fingers..for example, if he draws a circle, an 'S' letter, an expiral, etc.

I'm already familiar with touch events and I'm capable of reading the coordinates... my problem Is in finding algorithms and information about the recognition of the patterns with some degree of error.... for example, If I'm supposed to detect a circle I should detect it even if the user didn't did a make perfect one.

Any resources in the matter?, thanks !

Answer 1

This site demos a very simple, easy to implement gesture recognizer, which they wrote in Javascript. I've implemented it myself in another language, and found it quite easy to deal with. They've got code, and a paper describing the algorithm; everything you could need.