High pass filtering is used to detect the edges or sup pros the low$-$frequency noise in an image. At times, high pass filters are also used to sharpen the edges of an image. An image sharpening technique a $2$D second derivative or Laplacian filter is given as:

$g(x,y)=f(x,y)+c[gra{d}^{2}f(x,y)]$

CardiffMet $|$ MetCaerdydd

$4$

where $f(x,y)$ and $g(x,y)$ are the input and sharpened images, respectively while $gra{d}^{2}f(x,y)$ represents the Laplacian of the input image. The constant $c=-1$ if the following Laplacian filter mask is used:

$\backslash$table$[[0,1,0],[1,-4,1],[0,1,0]]$