1. A method of processing an image, comprising: decomposing the image into a plurality of channels, each being characterized by a different depth-of-field; accessing a computer readable medium storing an in-focus dictionary defined over a plurality of dictionary atoms, and an out-of-focus dictionary defined over a plurality of sets of dictionary atoms, each set corresponding to a different out-of-focus condition; and computing at least one sparse representation of said decomposed image over said dictionaries.