A modified parallel thinning algorithm

A parallel thinning algorithm of C.M. Holt et al. (1987) is compared with an algorithm of D. Rutovitz (1966) and one by T.Y. Zhang and C.Y. Suen (1984). Analyses and experiments show that the Holt algorithm is similar to the Rutovitz algorithm. A heuristic modification to Rutovitz' algorithm is also proposed and the modified algorithm is faster than Holt's algorithm.