Refer to Section 6.7.3. One might think that a logical approach for defining the gradient...

Refer to Section 6.7.3. One might think that a logical approach for defining the gradient of an RGB image at any point (x, y) would be to compute the gradient vector (see Section 3.6.4) of each component image and then form a gradient vector for the color image by summing the three individual gradient vectors. Unfortunately, this method can at times yield erroneous results. Specifically, it is possible for a color image with clearly defined edges to have a zero gradient if this method were used. Give an example of such an image. (Hint: Set one of the color planes to a constant value to simplify your analysis.)