Boundary-labeling algorithms for panorama images

  • Authors:
  • Andreas Gemsa;Jan-Henrik Haunert;Martin Nöllenburg

  • Affiliations:
  • Karlsruhe Institute of Technology;Universität Würzburg;Karlsruhe Institute of Technology

  • Venue:
  • Proceedings of the 19th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems
  • Year:
  • 2011

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Abstract

Boundary labeling deals with placing annotations for objects in an image on the boundary of that image. This problem occurs frequently in situations where placing labels directly in the image is impossible or produces too much visual clutter. Previous algorithmic results for boundary labeling consider a single layer of labels along some or all sides of a rectangular image. If, however, the number of labels is large or labels are too long, multiple layers of labels are needed. In this paper we study boundary labeling for panorama images, where n points in a rectangle R are to be annotated by disjoint unit-height rectangular labels placed above R in k different rows (or layers). Each point is connected to its label by a vertical leader that does not intersect any other label. We present polynomial-time algorithms based on dynamic programming that either minimize the number of rows to place all n labels, or maximize the number (or total weight) of labels that can be placed in k rows for a given integer k. For weighted labels, the problem is shown to be (weakly) NP-hard, and we give a pseudo-polynomial algorithm to maximize the weight of the selected labels. We have implemented our algorithms; the experimental results show that solutions for realistically-sized instances are computed instantaneously.