Geometric Constructions in the Digital Plane

  • Authors:
  • Peter Veelaert

  • Affiliations:
  • Hogeschool Gent, Department of INWE, Schoonmeersstraat 52, B-9000 Ghent, Belgium. peter.veelaert@hogent.be

  • Venue:
  • Journal of Mathematical Imaging and Vision
  • Year:
  • 1999

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Abstract

We adapt several important properties from affine geometry so that they become applicable in the digital plane. Each affine property is first reformulated as a propertyabout line transversals. Known results abouttransversals are then used to derive Helly typetheorems for the digital plane. The main characteristic of a Helly type theorem isthat it expresses a relation holding fora collection of geometricobjects in terms of simpler relations holding for some of the subcollections. For example, we show that in the digital plane a collection of digital linesis parallel if and only if each of its 2-membered subcollectionsconsists of two parallel digital lines. The derived Helly type theorems lead to many applications in digitalimage processing. For example, they provide an appropriate setting for verifying whetherlines detected in a digital image satisfythe constraints imposed by a perspective projection. The results can be extended to higher dimensions or to other geometric systems, such as projective geometry.