Digital distances and integer sequences

  • Authors:
  • Nicolas Normand;Robin Strand;Pierre Evenou

  • Affiliations:
  • IRCCyN UMR CNRS 6597, Polytech Nantes, LUNAM Université, Université de Nantes, Nantes Cedex 3, France;Centre for Image Analysis, Uppsala University, Sweden;IRCCyN UMR CNRS 6597, Polytech Nantes, LUNAM Université, Université de Nantes, Nantes Cedex 3, France

  • Venue:
  • DGCI'13 Proceedings of the 17th IAPR international conference on Discrete Geometry for Computer Imagery
  • Year:
  • 2013

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Abstract

In recent years, the theory behind distance functions defined by neighbourhood sequences has been developed in the digital geometry community. A neighbourhood sequence is a sequence of integers, where each element defines a neighbourhood. In this paper, we establish the equivalence between the representation of convex digital disks as an intersection of half-planes ($\mathcal{H}$-representation) and the expression of the distance as a maximum of non-decreasing functions. Both forms can be deduced one from the other by taking advantage of the Lambek-Moser inverse of integer sequences. Examples with finite sequences, cumulative sequences of periodic sequences and (almost) Beatty sequences are given. In each case, closed-form expressions are given for the distance function and $\mathcal{H}$-representation of disks. The results can be used to compute the pair-wise distance between points in constant time and to find optimal parameters for neighbourhood sequences.