1. A method of selecting a sub-set of image elements of a digital image based on a visual attribute of the image elements, the method including the steps of: providing a set of lexical classifiers that characterize said visual attribute; selecting a lexical classifier from said set of lexical classifiers as a reference lexical classifier; determining a lexical classifier for each of said image elements; comparing the lexical classifier associated with each of said image elements with the reference lexical classifier; and selecting an image element as part of said sub-set of image elements if the lexical classifier of said image element corresponds to the reference lexical classifier.