Digital Steiner sets and Matheron semi-groups

There are various ways to define digital convexity in ZnZn. The proposed approach focuses on structuring elements (and not the sets under study), whose digital versions should allow to construct hierarchies of operators satisfying Matheron semi-groups law γλγμ=γmax(λ,μ)γλγμ=γmax(λ,μ), where λλ is a size factor. In RnRn the convenient class is the Steiner one. Its elements are Minkowski sums of segments. We prove that it admits a digital equivalent when the segments of ZnZn are Bezout. The conditions under which the Steiner sets are convex in ZnZn, and are connected, are established. The approach is then extended to structuring elements that vary according to the law of perspective, and also to anamorphoses, so that the digital Steiner class and its properties can extend to digital spaces as a sphere or a torus.