The Laplacian filter is used for detection of edges in an image. It highlights areas in which intensity changes rapidly producing a picture of all the edges in an image.


Name   Default   Description
Radius 0.8 pixels

This value determines the size of the edges that are detected.

This value represents the standard deviation of the Laplacian of Gaussian function.

How it Works

The Laplacian filter is a standard Laplacian of Gaussian convolution. This is a second derivative function designed to measure changes in intensity without being overly sensitive to noise. The function produces a peak at the start of the change in intensity and then at the end of the change.

Because the Laplacian of Gaussian produces a fairly wide convolution for a small radius this filter can become quite computationally expensive as radius is increased.


The following examples show the effect of a Laplacian filter applied with a number of different settings.



Original Image before Laplacian Filter



Laplacian Radius 0.8 Pixels



Laplacian Radius 1.6 Pixels



Laplacian Radius 3.2 Pixels