Face detection and cropping

[Tauren Mills]

Anyone have thoughts on how to best implement a tool that could detect
faces in an image and automatically give suggested crop sizes?

Here's a cool face detection tool:
https://github.com/jaysalvat/jquery.facedetection
Demo: http://facedetection.jaysalvat.com/

I believe it uses HTML5 canvas features, so it would not be as cross-
browser compatible as JCrop is.

My use case is that users will be uploading images of themselves to be
printed onto ID cards using a card printer. The requirement is that
the face consumes about 50 to 60% of the image and that it is
centered. They should end up as passport-style photos.

I'm open to any ideas...