In image procesing, smoothing an image removes some of the fine detail. This may be used to remove noise or to look at different levels of detail, notably in a Laplacian-of-Gaussian filter. Smoothing filters may be a very simply averaging of an NxN area of pixels, or more complex such as applying a Gaussian filter.
Defined on page 245
Used on pages 245, 248
Applying a 2 x 2 smoothing filter