Abstract: For the shortcoming of non-single pixels and broken points in the obtained image boundary, a new algorithm for boundary tracing of dual layer boundary region growing is proposed, to search inner-points and outer-points around center-points, to combine the inner-points with upper outer-points, to conduct continuous tracing with the combined points as the center-points in next search. The algorithm takes into account the one-way search from initial points, and can fill the broken points in one tracing process. Thus, it effectively makes up the defects of memory reptile method and eight neighborhood method in tracing embranchment, broken point and thick boundary. The experiments prove its effectiveness.

Key words: region growing, boundary tracing, reptile, eight neighborhood