Laplacian operator

The Laplacian operator, written ∇², is used in image processing. It is the second differential of the intensity of the image. In areas with slower constant changes in intensity the Laplacian is small, but where this changes, typically at the boundaries of objects, it is large. It is therefore useful as part of edge detection algorithms. The theoretical Laplacian is based on a functions of continuous variables, but this approximated on the pixels of a real image using a linear operator.