Patent ID: 7720256

Claim:
A method of processing postal objects, in which during a first sorting pass of postal objects, a first digital image of a certain level of resolution is formed of a surface of each object including postal address information for generating first image signatures recorded as object identifiers in a system for automatically evaluating postal addresses and directing said postal objects towards corresponding sorting outlets, and in which during a second sorting pass of said postal objects, a second digital image of said level of resolution is formed of the surface of each current postal object for generating a current image signature and in which said recorded first signatures are browsed in said system to detect a matching with said current signature, wherein each image signature generated from a postal object digital image including postal address information comprises a first component representative of physical characteristics of the digital image and a second component representative of characteristics of the address information in said image, wherein said first component comprises at least an overall attribute relating to the image as a whole and local attributes relating to distinct portions of said image, wherein said method further comprises the steps of: lowering the resolution of said digital image to a low-frequency level to produce a low-frequency digital image, subdividing said low-frequency digital image into several sets of image portions of different sizes corresponding respectively to different scales of subdivision and extracting from each image portion at least a histogram representative of a distribution of the luminance values of pixels in said image portion to generate said local attributes of each image signature, and performing initial filtering among said first signatures by comparing said overall attribute of said current signature with said overall attribute of first signatures so as to provide candidate first signatures and after that comparing local attributes of said current signature with local attributes of said candidate first signatures to detect a matching, said comparison of local attributes being based on a computing of sliding normalized coefficient.