Modified watershed algorithm considering zero-crossing point of gradient

In this paper, we propose a modified watershed algorithm considering zero-crossing point of gradient to obtain a correct edge of a region. The conventional watershed algorithm decides priority considering gradient of a region to be extended. However if the gray levels of two neighboring seeds are quite different, the ridge line obtained by the conventional watershed algorithm is not coincided with the correct edge. It is probable that the point where gray level extreme value occurs will be estimated as an edge of two neighboring regions. Therefore more correct edge of a region can be obtained if the expansion of watershed algorithm is delayed where the gray level extreme value occurs. The position where the gray level extreme value occurs corresponds to the position where the zero-crossing of gradient occurs. So we adjust the priority to postpone expansion at the zero-crossing point of gradient. We compare the proposed method with the conventional method and validate that this proposed method can extract more correct edge of a region.