The application of the Roberts cross operator to the image of the square is shown in Figure 4.6.
The two templates provide the results in Figure 4.6(a) and (b) and the result delivered by the
Roberts operator is shown in Figure 4.6(c). Note that the corners of the square now appear in
the edge image, by virtue of the diagonal differencing action, whereas they were less apparent
in Figure 4.2(d) (where the top left corner did not appear).
(a) M
(b) M
+
(c) M
Figure 4.6 Applying the Roberts cross operator
An alternative to taking the maximum is simply to add the results of the two templates
together to combine horizontal and vertical edges. There are of course more varieties of edges
and it is often better to consider the two templates as providing components of an edge vector:
the strength of the edge along the horizontal and vertical axes. These give components of a
vector and can be added in a vectorial manner (which<