1. A non-transitory processor-readable medium storing code representing instructions that when executed by a processor cause the processor to: for a first image, calculate a first vector of similarity to a set of two-dimensional reference images as a first face descriptor; for a second image, calculate a second vector of similarity to the set of reference images as a second face descriptor; calculate a similarity measure between the first face descriptor and the second face descriptor; wherein calculating a vector of similarity to a set of reference images comprises calculating a vector of similarity to a plurality of facial images for each of a plurality of reference individuals; wherein calculating a first vector of similarity to a set of reference images comprises: calculating, using a visual similarity algorithm, a visual similarity value between the first image and each facial image in the set of reference images; and for each reference individual in the set of reference images, choosing the maximum visual similarity value; and, wherein calculating a second vector of similarity to a set of reference images comprises: calculating, using a visual similarity algorithm, a visual similarity value between the second image and each facial image in the set of reference images; and for each reference individual in the set of reference images, choosing the maximum visual similarity value.