Mr. Huang,
I have a question I was hoping you might help with. It actually has nothing to do with physics, but I'm in the process of coding a neural network that can read 'hand'-written (or rather, mouse-written) characters. Ironically, while creating a neural network was no problem, I couldn't figure out how to do something you did in the applet up there. I was wondering how you managed to detect the colour of a given pixel.

If you could either point me in the right direction, or even better, if you'd be willing to send the source code, I'd be greatly appreciative. Thanks!