Comment on “elimination of redundant operations for a fast Sobel operator”

It is shown that a further reduction in the number of storage places and additions can be obtained by a slight modification of the method given by Lee (ibid., vol.SMC-13, no.2, p.242-5, 1983). In reply, Lee expresses appreciation for the improvement of the 1-D method by the partial difference and shows that Picton´s comment about the 2-D method is incorrect in two cases. Lee shows that another partial difference needs to be used for storage efficiency if an image plane has fewer rows than columns.