Walking in the farey fan to compute the characteristics of a discrete straight line subsegment

  • Authors:
  • Isabelle Sivignon

  • Affiliations:
  • CNRS, UMR 5216, gipsa-lab, France

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

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Abstract

Given a Digital Straight Line (DSL) of known characteristics (a,b,μ), we address the problem of computing the characteristics of any of its subsegments. We propose a new algorithm as a smart walk in the so called Farey Fan. We take profit of the fact that the Farey Fan of order n represents in a certain way all the digital segments of length n. The computation of the characteristics of a DSL subsegment is then equivalent to the localization of a point in the Farey Fan. Using fine arithmetical properties of the fan, we design a fast algorithm of theoretical complexity $\mathcal{O}(\log(n))$ where n is the length of the subsegment. Experiments show that our algorithm is faster than the one previously proposed by Said and Lachaud in [15,14] for "short" segments.