PARALLEL REDUCTION OPERATORS FOR GRAY-TONE PICTURES

Abstract

Reduction operators iteratively applied to gray-tone pictures cause dilation of the regions, the gray-value of which is locally minimal, so that a gray-tone picture with no distinction between foreground and background is transformed into a set of bottom regions separated by ridge lines. The set of ridge lines can be understood as the skeleton of what is perceived as foreground. We describe a two-subiteration parallel skeletonization algorithm employing new reduction operators which are based on the nonridge point condition and are topology preserving. The performance of the algorithm is discussed, in particular with respect to certain critical configurations, and experimental work is reported to evaluate the thinning capability of the proposed reduction operators.