[PD] mean color value of a video grid

Dear list, I am searching for a solution to this problem :

• given that a video stream - grey scale - is divided in say 8

rectangles-zones constituting a grid.

• compute a time-varying mean value (over space) of the degree of

illumination (or shading) of each zone.

i am right now thinking of a combination of :

pix_video (to read a stream from a webcam e.g.) 8 pix_crop (to divide the image) pix_snap to take a snapshot as a picture. pix_mean_color to compute the mean value.

This should work but i am may be missing some more direct way of doing this... Moreover would it be possible to compute these values on a more complex shape than a rectangle?

as one can see, i will probably use Gem as it's the easiest to run and install on osx but i wonder if it won't be easier or more straightforward to code with gridflow or pdp?

vincent