A ternary relation for structuring the digital plane

Abstract

We discuss certain ternary relations, called plain, and show that each of them induces a connectedness on its underlying set. This connectedness allows for definitions of concepts of simple closed and Jordan curves. We introduce a particular plain ternary relation on the digital plane Z^2 and, as the main result, we prove a digital analogue of the Jordan curve theorem for the connectedness induced by this relation. It follows that the ternary relation introduced may be used as a convenient structure on the digital plane for the study of the geometric properties of digital images that are related to boundaries because boundaries of objects in digital images are represented by digital Jordan curves. An advantage of this structure over the Khalimsky topology is that it allows Jordan curves to turn at the acute angle /4 at some points.

V práci jsou diskutovány jisté ternární relace, které jsou nazvány jednoduché, a je ukázáno, že každá z nich indukuje souvislost na své nosné množině. Pozornost je pak věnována jisté speciální jednoduché ternární relaci na digitální rovině Z^2. Jako hlavní výsledek je dokázána Jordanova věta pro souvislost indukovanou touto relací.