1. A method of identifying computer graphics in digital images, the method comprising: extracting a first set of features from an input digital image, said extracting comprising: applying a discrete transformation to decompose the input digital image into a set of sub-bands; and obtaining sets of moments of characteristic functions associated with the sub-bands and with the input digital image, wherein said sets of moments are used to form said first set of features; extracting a second set of features from a prediction-error image derived from said input digital image; and applying a classification algorithm to said first set of features and said second set of features to determine if the combined sets of features indicate that the input digital image corresponds to computer graphics.