Résumé en anglais

Based on the phenomenological description of Gaetano Kanizsa, we discuss the physical generation process of images as a combination of basic operations: occlusions, transparencies and constrast changes. These operations generate the essential singularities, which we call junctions. We deduce a mathematical and computational model to detect the "atoms" of the image: level lines joining T- or X-junctions. Then we propose the adequate modification of morphological filtering algorithms so that they smooth the "atoms" without altering the junctions. Finally, we give some experiments on real and synthetic images.