Contour tracing for precision measurement

Current methods of contour tracing are based on chain code concepts which require movement from the center of a pixel to the center of a four- or eight-connected neighbor. They are basically serial processes requiring memory and decision structures based on the connectedness of the objects and the direction of the trace. A chain code method is proposed here which moves along the edge midpoints of pixels, increasing the number of contour samples. This new tracing process needs no memory, lends itself to fast table lookup implementation, uses only two tables for all connectedness rules and trace directions, and permits parallel preprocessing. The resulting chain code is nearer the true contour than any previous digital contour tracing method. Methods for conversion between the standard chain code and the new edge chain code are also presented.