Improving the visual aspect of the skeleton and simplifying its structure

The distance-labeled skeleton is a well-known shape representation system that can be used profitably in the framework of shape analysis. A large number of skeletonization algorithms are available in the literature, which are all more or less affected by problems that could limit the actual use of the skeleton for applications. Aim of this contribution is to suggest how to improve the visual aspect of the skeleton and to simplify its structure. In particular, we present tools that can be used to 1) straighten zig-zags possibly present along skeleton branches, 2) replace each set of branch points sufficiently close to each other by the centroid of the zone of influence of the set of branch points, 3) prune branches originating from scarcely significant object's protrusions or arising in correspondence with weak convexities of the object's boundary, 4) perform a polygonal approximation of skeleton branches by taking into account both the changes of curvature along the skeleton branches and the variations in local thickness of the object's regions into which the skeleton branches are mapped, and 5) build a simplified version of the skeleton, where each skeleton branch consists of a sequence of hinged straight-line segments along each of which the distance values of the skeleton points either assume a unique value or assume values that are monotonically increasing or monotonically decreasing.