I took the liberty of extracting the interesting bits of this into a reusable class, and tossed it up on GitHub:

https://github.com/aaronbrethorst/ColorArt

If I have the time this afternoon, I'll port it over to iOS, too. Or, if someone feels inclined to do so, I welcome pull requests :)

Edit: and I transferred the repo over to Panic. I'm maintaining a fork so the link above doesn't go dead.