the überawesome guys Lluis Gomez i Bigorda and Yves Degoyon put lots of effort in developing opencv extentions for pd. some new objects are available and luckily now a precompiled version for osx! it should run on linux as well, windows i'm afraid not.

so, finally i was able to run a face detection in pd today. thank you so much!

http://hangar.org/wikis/lab/doku.php?id=start:puredata_opencv