Question

Question from Digital Imaging Processing

6. a The compass gradient operators of size 3x3 are designed to measure gradients f edges oriented in eight directions: E, NE, N, NW, W, SW, S, and SE. i) Give the form of these eight operators using coefficients valued 0, 1 or -1 ii) Specify the gradient vector direction of each mask, keeping in mind that the gradient direction is orthogonal to the edge direction.

Answer 1

Pewitt Makk3 1시 0 N W こTaわ 31-333SS These ate Compaßs a for kiseh

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• Another way of finding out edge location is by using masks. The following figure defines eight gain-normalized compass gradient impulse response arrays (masks) for Kirsch operator. The compass names indicate the slope direction of maximum response. The edge magnitude is given by the maximum response obtained after convolving all these eight masks with the image and choosing the one with the highest value. The edge angle is determined by the direction of the largest gradient.

the one explained in first page is best

where GR(i, j) and GC(i, j) are gradients along row and column directions at location (i, j). Generally gradients are computed in row, column, and diagonal directions. For computational efficiency the gradient amplitude is approximated by their magnitude combination given by the following equation