Compute FCOl and FC02 as follows:
The FCOl and FC02 kernels function as horizontal and vertical edge detectors, respectively. The J2 coefficients compensate for the separation between the central pixel and corner pixel, so that the kernel's response to edges that are not horizontal or vertical is the same as it is to aligned edges.
The FC03 and FC04 operators are what Frei and Chen call "ripple" detectors, since they are insensitive to edges and produce the largest output with irregular patterns, or ripples:
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