3 0 0 1 2 0 1 0 2 0 3 0 2 1 0 0 1 2 0 0 3 2 0 1 0 2 1 1 1 1 / Gradient of Laplace 1 1 1 1 1 1 0 0 0 1 0 0 0 1 1 0 0 0 1 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 1 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0