1. A method for assigning one of a plurality of classes to an input image, comprising: identifying a plurality of key-patches in the input image; computing a feature vector for each of (at least ones of) the plurality of key-patches; computing a histogram for each of (at least ones of) the plurality of classes using the plurality of feature vectors computed; assigning at least one of the plurality of classes to the input image using the plurality of histograms computed as input to a classifier.