Robert's operator is a non-linear filter to detect the presence of lines in an image. It works on each 2x2 portion of the scene and is defined as the sum of the absolute differences between opposing corners:
G(x,y) = | f(x,y) − f(x+1,y-1) | + | f(x+1,y) − f(x,y-1) |
G(x,y) = | f(x,y) − f(x+1,y-1) | + | f(x+1,y) − f(x,y-1) |
Used in Chap. 12: pages 167, 168, 169
Robert's operator: (i) G = |3−3|+|3−3| = |0|+|0| = 0 (ii) G = |7−2|+|3−8| = |5|+|−5| = 10 (iii) G = |5−6|+|7−1| = |−1|+|6| = 7 (iv) G = |7−8|+|1−2| = |−1|+|−1| = 2