1. A method, comprising: detecting in an input image a face region containing at least a portion of a person's face; identifying in the input image an auxiliary identification region outside the face region; determining facial features characterizing the face region; calculating auxiliary identification features characterizing the auxiliary identification region; deriving an indexing datum from the facial features and the auxiliary identification features; and storing the indexing datum in association with the input image; wherein the detecting, the identifying, the determining, the calculating, the deriving, and the storing are performed by computing hardware.