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Sobel and Prewitt operators

Named 3x3 kernels approximating the image gradient with built-in perpendicular smoothing.

The Sobel and Prewitt operators are separable 3\times 3 kernels combining a central-difference pass in one direction with an averaging pass in the perpendicular direction, Sobel weighting its center row twice as heavily for slightly better noise resistance.

See also

discrete image gradient
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