From KDE Community Wiki

Face Detection and Recognition will be integrated in digiKam as part of GSoC 2010, by Aditya Bhatt and mentor Alex Jironkin.

Short Description

The main purpose of Face Detection is to easily be able to tag faces in photos with names of individuals. Face Recognition, on the other hand, helps in automating this process by automatically tagging unidentified faces with already named faces.

Where is the code?