[PD] noob question: alpha channel multiplication

[michal panaak]

hi pd people!

i'm working on this project:

the basic idea is to create an interactive installation, where anyone 
could move around with a bluescreen behind his back, while in front of 
him, there would be a projection screen with a huge crowd of clones of 
oneself facing the performer..

i need to capture a person in front of a bluescreen, create alpha 
channel of the person, multiply it and import it into a picture (for 
example a picture of some plaza) so that it would look like a regiment 
of clones moving around in a grid.. in perspective..

i think i'd need functions pix_alpha / pix_chroma_key / pix_mask for the 
alpha channel processing.. and then some other GEM functions to multiply 
it and create a grid inside a picture.. but i'm not sure exactly how..

all i ask is to kick me in the right direction..

-mp-