I second the idea with cam. GEM can do blobanalysis but if you a
programmer I recommend to have a look at OpenCV library which can,
amoung other things, do multiblob analysis. Its the base for Eyesweb
software which is unfortunately Windows only. I use OpenCV in several
interactive projects, but so far more for installations.
Cheers,
Malte
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Malte Steiner
http://www.block4.com
media art + development