A method of processing postal articles wherein a first digital image of an article is formed at a resolution of 2 pixels/mm to 10 pixels/mm and a first image signature (SigP i) is derived from this first image, which signature is a unique identifier for said article, and in which a current digital image for said article is formed again and a current signature (SigC) is derived from the current image and compared with first signatures of article images stored in memory in a data processor unit in order to pair-off the current signature with one of the first signatures on the basis of similarity, the method being characterized in that each signature is derived from a digital image by the following steps: • extracting a digital map of the luminance gradient field of said image by local planar regression with a local matrix, e.g. of 5×5 pixels, and with or without overlap, so as to smooth surface deformations of the postal article in the gradient field map, and so as to enhance the symbol information contained in the image, such as text characters and high-contrast graphics; • identifying in said digital map the most robust points of interest, which are the topological singularities of the gradient field having the greatest amplitude of the vector field, and which correspond to a local circular divergence extremum of the gradient field that appears in concave regions of the symbol elements in the image or at the ends of symbol elements in the image such as the alphanumeric characters of the destination address block; and • representing points of interest in memory by means of digital descriptors (DOGS), each of which is representative, for a certain point of interest: a) of a spatial position of a point of interest in said image; b) of a signed singularity index that is calculated from a combination of various physical magnitudes including a mean value of circular divergence of the gradient field and of the mean amplitude of the gradient field in a pixel analysis window of the image centered on said certain point of interest; and c) accumulating singularity indices calculated on the rings of a circular local neighborhood disk centered on said certain point of interest. • extracting a digital map of the luminance gradient field of said image by local planar regression with a local matrix, e.g. of 5×5 pixels, and with or without overlap, so as to smooth surface deformations of the postal article in the gradient field map, and so as to enhance the symbol information contained in the image, such as text characters and high-contrast graphics; • identifying in said digital map the most robust points of interest, which are the topological singularities of the gradient field having the greatest amplitude of the vector field, and which correspond to a local circular divergence extremum of the gradient field that appears in concave regions of the symbol elements in the image or at the ends of symbol elements in the image such as the alphanumeric characters of the destination address block; and • representing points of interest in memory by means of digital descriptors (DOGS), each of which is representative, for a certain point of interest: a) of a spatial position of a point of interest in said image; b) of a signed singularity index that is calculated from a combination of various physical magnitudes including a mean value of circular divergence of the gradient field and of the mean amplitude of the gradient field in a pixel analysis window of the image centered on said certain point of interest; and c) accumulating singularity indices calculated on the rings of a circular local neighborhood disk centered on said certain point of interest. a) of a spatial position of a point of interest in said image; b) of a signed singularity index that is calculated from a combination of various physical magnitudes including a mean value of circular divergence of the gradient field and of the mean amplitude of the gradient field in a pixel analysis window of the image centered on said certain point of interest; and c) accumulating singularity indices calculated on the rings of a circular local neighborhood disk centered on said certain point of interest.