What Does Digital Straightness Tell about Digital Convexity?

  • Authors:
  • Tristan Roussillon;Laure Tougne;Isabelle Sivignon

  • Affiliations:
  • Université de Lyon, Université Lyon 2, LIRIS, UMR5205, FRANCE F-69676;Université de Lyon, Université Lyon 2, LIRIS, UMR5205, FRANCE F-69676;Université de Lyon, CNRS, Université Lyon 1, LIRIS, UMR5205, FRANCE F-69622

  • Venue:
  • IWCIA '09 Proceedings of the 13th International Workshop on Combinatorial Image Analysis
  • Year:
  • 2009

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Abstract

The paper studies local convexity properties of parts of digital boundaries. An online and linear-time algorithm is introduced for the decomposition of a digital boundary into convex and concave parts. In addition, other data are computed at the same time without any extra cost: the hull of each convex or concave part as well as the Bezout points of each edge of those hulls. The proposed algorithm involves well-understood algorithms: adding a point to the front or removing a point from the back of a digital straight segment and computing the set of maximal segments. The output of the algorithm is useful either for a polygonal representation of digital boundaries or for a segmentation into circular arcs.