Thinning in a distributed environment

In the digitization of survey maps where the components are sparse but occupy large areas, a serial thinning algorithm implemented on a distributed environment can yield a better speedup than is possible with other forms of parallelism. A distributed algorithm based on contour generation is described. A component is divided into rectangular sections and assigned to different processors. A block-resume synchronization mechanism is examined. The different contour configurations at the border of a section are identified. The amount of communication between neighboring sections can be kept to a minimum by chain code representations. The proposed synchronization mechanism has been incorporated in the contour generation thinning algorithm and has been simulated on a Sun/4 workstation. For images such as contour maps, the extra overhead needed for synchronization is not significant