“…Skeletal abstraction is a difficult problem that has been greatly studied over years; and obviously it is out of the paper scope. Briefly saying, existing methods for extracting skeletons concern broad research areas comprising topological thinning algorithms (Arcelli and Baja, 1985;Lee and Kashyap, 1994;Borgefors et al, 1999;Bertrand and Couprie, 2009) where Blum grassfire transform (Blum, 1973) were used, curve evolution, variational and wavefront propagation methods (Leymarie and Levine, 1992;Geiger et al, 2003;Tek and Kimia, 2003), Voronoi diagram (Schmitt, 1989;Ogniewicz, 1993;Sheehy et al, 1996), and methods using Euclidean distance function computed for example with the Eikonal equation or Hamilton-Jacobi systems (Siddiqi et al, 2002;Torsello and Hancock, 2003;2004). For more information on that subject, interested readers can have a look on those references.…”