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# Tag Info

I think the first smoothing, by $\sigma_D$, is only done to get more stable derivatives whereas in the second step the convolution by a Gaussian with $\sigma_I$ is done to establish the 'scale-space' in which the operator is applied. Ignoring $\sigma_D$, this looks like this in Matlab: dx = [-1 0 1; -1 0 1; -1 0 1]; % Simple mask for derivative Ix = ...