1. An image processing method comprising the steps of: partitioning an image under test to form a plurality of image segments, each segment representing a set of pixels having similar image properties, at least some segments being contiguous; deriving feature data from a subset comprising one or more of the image segments; comparing the feature data from the subset of image segments with feature data indicative of respective reference image segments so as to detect a degree of similarity between the image segments under test and the reference image segments.