1. A computer-implemented method of processing a fingerprint image, comprising: acquiring a present fingerprint image from a fingerprint sensor and computing a plurality of first feature vectors of the present fingerprint image; retrieving a plurality of second feature vectors of an enrolled fingerprint image from a storage; applying a similarity measure to compute a plurality of similarity values that represents a degree of similarity between a set of first feature vectors and second feature vectors; performing first classification of at least a portion of the plurality of similarity values to generate a first signal indicative of whether the present fingerprint image falls within a class defined from enrolled images; performing second classification of at least a portion of the plurality of similarity values to generate a second signal indicative of whether the present fingerprint image falls within a class of fingerprints from live fingers or a class of fingerprints from imitated fingers; and generating an authentication signal from the first signal and the second signal.