Green screen / chroma key iOS

I am trying to do green screen subtraction in real time on iOS. I have included openCV in my project and I can get the raw data from the camera using this tutorial: http://www.benjaminloulier.com/articles/ios4-and-direct-access-to-the-camera Then after I convert from CGImageRef to IplImage. What I am stuck at is, using openCV, how can I do this green screen subtraction? Or is there a simpler image library I ca开发者_如何学Pythonn use for iOS to achieve this?

Thanks

EDIT: Link broken. Looks like the company may have folded.

Here is a Chroma Key package that (supposedly) supports iOS:

https://tastyblowfish.com/chromagic/index.html

It is a commercial package - I'm not associated with them.

For those looking for an answer to this, I ended up using openCV. It's works great (for an iPhone app). Take a look at the source code in the description of this video: http://www.youtube.com/watch?v=aE0F4F5WIuI