Hello, well the next step is to write some software that understands images, and translates them into motor movements! Easy, right?

Since you are on the polargraph website, I'm going to assume you've tried using the Polargraph software. Now, if you're looking to dig into the code, that's not so easy in Polargraph. Not that it is more complicated, or more clever than any other code, it just does a little _more_ stuff, and to be honest, it's not written in a very accessible, readable way. You will need to hack it a little to get the motor connections working.

A better starting point, from a coding perspective is Dan Royer's drawbot project (http://www.marginallyclever.com/blog/category/drawbot-my-creations/). His firmware is clear and nicely written, and nicely readable. You'll still need to mod it to use your motor driver connections (it is set up to use an adafruit motorshield). I haven't looked at the java app that he uses on the image generation side, but imagine it will be decent too.

Alex Weber (Tinkerlog)'s Der kritzler (http://tinkerlog.com/2011/09/02/der-kritzler/) is the other main option. If you are a unixy kind of guy you will like it. It is also very nicely written, clear.

If you want to write your own code, brush up on your pythagoras, and that's about it. Look at the above to see how other people structure their projects.

good luck!
sn