Abstract:A method of region labeling for two-value digital image is developed in the paper. The minimum sets of complete graphs are obtained respectively for 8-site neighborhood and 4-site neighborhood digital images. Based on basic graphs of image labeling, an automaton, with the vertex chain code as its outputs, for the boundary recognition of the two-value digital images is constructed. The automaton for region labeling is an efficient method to label regions in two-value digital images.