Using OpenCV for Processing is very powerful and a lot of fun to play around with. This Instructable will help you get it installed on your computer and go over some of the capabilities of the face tracking sketch.
Step 1: Install OpenCV Library for Processing
Follow the steps that are outlined on the website. After you have installed it and moved it into your Processing libraries folder, open up Processing. If you don't know where this is, go to
Processing => Preferences
and the sketchbook location is listed at the top.
Go to this folder location. In it you should see a folder called libraries. If it isn't there, don't worry, you just have to make a new folder in that location and name it libraries. Move the OpenCV folder into your libraries folder.