1. A method for deriving a descriptor of an interest point in an image having a plurality of pixels, the interest point having a location in the image and an orientation, the method comprising: identifying a neighbourhood around the interest point aligned with the orientation of the interest point, the neighbourhood comprising a set of pixels; inspecting contrasts in the neighbourhood of the interest point in at least one direction having a fixed relation to the orientation using at least one digital filter to thereby generate first scalar contrast measures for each direction independently, and generating a multidimensional descriptor comprising first elements, each first element being a second scalar contrast measure that is a combination of the first scalar contrast measures from only one direction.