  This communication describes a representation of images as a set of edges
characterized by their position and orientation. This representation allows the
comparison of two images and the computation of their similarity. The first
step in this computation of similarity is the seach of a geometrical basis of
the two dimensional space where the two images are represented simultaneously
after transformation of one of them. Presently, this simultaneous
representation takes into account a shift and a scaling ; it may be extended to
rotations or other global geometrical transformations. An elementary
probabilistic computation shows that a sufficient but not excessive number of
trials (a few tens) ensures that the exhibition of this common basis is
guaranteed in spite of possible errors in the detection of edges. When this
first step is performed, the search of similarity between the two images
reduces to counting the coincidence of edges in the two images. The approach
may be applied to many problems of pattern matching ; it was checked on face
recognition.
