Residuals + directional GAPS = skeletons

Many thinning algorithms for 2D binary images, or modifications of existing ones, have been proposed in recent years. The one given herein is surprisingly simple compared to most of them, and still it has theoretically favorable properties. Actually, it provides a connected single-pixel in width whenever possible well-centered homototic skeleton that allows shapes to be nearly reconstructed. In addition to these properties, it is also very attractive because of its generalization to higher dimensions. The presented algorithm is based on the application of directional erosions, while retaining those pixels that introduce disconnections. It is shown how this strategy is specially well-suited for run-length encoded images, leading to a very fast and simple thinning algorithm. © 1997 Elsevier Science B.V.