Fast parallel thinning algorithms: parallel speed and connectivity preservation
A recently published parallel thinning approach [4] is evaluated. An improvement is suggested to enable preservation of certain diagonal lines which are not preserved by this algorithm. A unified notion of what is meant by an iteration (or subiteration) and parallel speed is presented, and with regard to its parallel speed this algorithm is argued to be comparable to other two-subiteration algorithms. The parallel speed of this algorithm is compared experimentally to the original algorithm that it improves [12] and it is shown that, unlike execution time on a specific machine, parallel speed is not improved. Finally, a more complete connectivity analysis is given illustrating sufficient additional conditions for applying fully in parallel the basic thinning operator used in both algorithms while maintaining all image connectivity properties.