A New Safe-Point Thinning Algorithm Based on the Mid-Crack Code Tracing

A new thinning algorithm for binary images, based on the safe-point testing and mid-crack code tracing, is presented in this paper. Thinning is treated as the deletion of nonsafe border pixels from the contour to the center of the object layer-by-layer. The deletion is determined by masking a 3 x 3 weighted template and by the use of look-up tables. The resulting skeleton does not require cleaning or pruning. The obtained skeleton possesses single-pixel thickness and preserves the object's connectivity. The algorithm is very simple and efficient since only boundary pixels are processed at each iteration and look-up tables are used.