Finding rotational symmetries by cyclic string matching
Josep Lladós1, Horst Bunke2, Enric
1Computer Vision Center - Dep. Informàtica.
Universitat Autònoma de Barcelona.
08193 Bellaterra (Barcelona)
2Institut für Informatik und Angewandte Mathematik. University
of Bern, Neubrückstr. 10,
CH-3012 Bern, Switzerland
Symmetry is an important shape feature. In this paper, a simple and
fast method to detect perfect and distorted rotational symmetries of 2D
objects is described. The boundary of a shape is polygonally approximated
and represented as a string. Rotational symmetries are found by cycling
string matching between two identical copies of the shape string. The set
of minimum cost edit sequences that transform the shape string to a cyclically
shifted version of itself define the rotational symmetry and its order.
Finally, a modification of the algorithm is proposed to detect reflectional
symmetries. Some experimental results are presented to show the reliability
of the proposed algorithm.
Keywords: Rotational Symmetry, Reflectional Symmetry, String