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. 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 3×3 weighted template and by the use of lookup 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 lookup tables are used