1. Process for the automatic recognition of objects liable to overlap, on the basis of respective reference images of said objects, and the image of a group of objects to be recognized, said images being stored in the form of digital values representing for each image the coordinates of the points of a contour line of said image, in a frame of reference, said process consisting of coding for each image, successive elementary segments, the ends of each elementary segment being substantially located on the same contour line, so that for each segment, said coding gives the length of said segment, as well as its angle with respect to a reference direction, said coding operation being performed both during a "learning" phase of the different objects to be subsequently recognized and in a subsequent "recognition" phase of the objects liable to overlap, wherein said process comprises in the learning phase the following steps: investigating for each reference image contour, pairs of successive or non-successive characteristic segments of said contour line, each formed from one or more elementary segments, said characteristic segments being oriented in a predetermined direction of the contour line, each pair determining a characteristic transition vector defined by parameters which include the value of an angle, oriented in the direction of the contour line, this angle being defined as the angle between the two oriented characteristic segments of the pair, the coordinates of the origin and the length of each characteristic segment of the pair, a transition vector being characteristic when its parameters provide a substantive discrimination of the contour of the corresponding object, even when said object is overlapped by one or more other objects, the parameters of the transition vectors being stored, hierarchizing the transition vectors of a contour as a function of their discrimination parameters, modifying said hierarchization of the transition vectors during the acquisition of the transition vectors of the contours of the different objects, so as to eliminate similar transition vectors for different contours, and said process comprising in the recognition phase the following steps: performing the same transition vector determination operation in the characteristic segments of the contour of the image of the objects to be recognized, comparing in the hierarchization order, the values of the parameters of the transition vectors of the contour of the image of the objects to be recognized and the contour of the reference images of each object, so as to investigate the similarities of the values of said parameters, forming a presence hypothesis of an object corresponding to a transition vector for which the comparison has established a similarity, and effecting a fine check of said hypothesis by comparing successive elementary segments of the contour of the reference image of said object with successive elementary segments of the contour of the image of the objects to be recognized.