13.3.5.5 Laplacian Filter

The Laplacian is used to enhance discontinuities. The 3x3 kernel is:

$$\left[ \begin{array}{r r r} 0 & -1 & 0 \\ -1 & 4 & -1 \\ 0 & -1 & 0 \\ \end{array} \right]$$

and the 5x5 is:

$$\left[ \begin{array}{r r r r r} -1 & -1 & -1 & -1 & -1 \\ -... ... & -1 & -1 \\ -1 & -1 & -1 & -1 & -1 \\ \end{array} \right]$$