User Guide

GNU Image Manipulation Program
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15.5.2 Difference of Gaussians
15.5.2.1 Overview
Figure 15.78: Applying example for the Difference of Gaussians filter
(a) Original image (b) Filter applied
You can find this filter through Filters → Edge detect → Difference of Gaussians
This filter is new in GIMP 2.2. It does edge detection using the so-called ‘Difference of Gaussians’ algorithm, which works by
performing two different Gaussian blurs on the image, with a different blurring radius for each, and subtracting them to yield the
result. This algorithm is very widely used in artificial vision (maybe in biological vision as well!), and is pretty fast because there
are very efficient methods for doing Gaussian blurs. The most important parameters are the blurring radii for the two Gaussian
blurs. It is probably easiest to set them using the preview, but it may help to know that increasing the smaller radius tends to give
thicker-appearing edges, and decreasing the larger radius tends to increase the ‘threshold’ for recognizing something as an edge.
In most cases you will get nicer results if Radius 2 is smaller than Radius 1, but nothing prevents you from reversing them, and
in situations where you have a light figure on the dark background, reversing them may actually improve the result.
15.5.2.2 Options
Figure 15.79: Gaussian Difference filter options