3 * 3 Sobel Matrix

NE-SW

E-W

NW-SE

N-S

0

1

2

−1

0

1

2

1

2

1

2

1

−1

0

1

−2

0

2

1

0

−1

0

0

0

−2

−1

0

−1

0

1

0

−1

−2

−1

−2

−1