Help! Anybody! How can I split and position a webcam's image ?

I've been trying to recreate a kaleidoscopic effect by splitting what it is grabbed by the webcam with jit.qt.grab. I just need to know how I can split the image and position the pieces. I understand how the coordinates system works when positioning, but I would really appreciate ANY help concerning the selection of a portion of the webcam, determing its size and positioning it. I've uploaded a picture of what I am trying to recreate, it shouldn't be that hard to make; it's just that I'm brand new to this!