ABSTRACT
Various applications of image processing and pattern recognition are based on the concept of skeletons (Siddiqi andPizer 2008).Thinning is an iterative object reduction until only the skeletons of the binary objects are left (Lam et al. 1992; Suen andWang 1994). Thinning algorithms in 2D serve for extractingmedial lines and topological kernels (Hall et al. 1996). A topological kernel is a minimal set of points that is topologically equivalent to the original object (Hall et al. 1996; Kong and Rosenfeld 1989; Kong 1995; Ronse 1988). Some thinning algorithms working on hexagonal grids have been proposed (Deutsch 1970; Deutsch 1972; Staunton 1996; Staunton 1999;Wiederhold and Morales 2008; Kardos and Palágyi 2011)
Parallel thinning algorithms are composed of reduction operators (i.e., some object points having value of “1” in a binary picture that satisfy certain topological and geometric constrains are changed to “0” ones simultaneously) (Hall 1996).
