A while back I thought it would be a good idea to implement face detection in Gallery2, based on a similar feature in Facebook. I downloaded the OpenCV computer vision toolkit and ran the facedetect sample app against a collection of 60 photos from my gallery, some with no faces, others with a single face, still others with multiple faces, faces in profile, etc. No matter which training file I used, the face detection was horribly unreliable.

This past weekend my little sister and I were going through the Facebook profiles of various cousins, and I noticed something about Facebook’s photo support that I somehow missed before: it automatically detects the presence of faces in each photo, and allows users to tag each face with the identity of its owner. Already-tagged faces have the owner’s name superimposed over the image.