Image Enhancement
SMOOTHING FILTERS - LOWPASS SPATIAL FILTERING
With the assumption that image pixel values within a small neighborhood are highly correlated and that the noise components are not correlated, noise may be reduced by replacing each pixel with the mean over a certain neighborhood of (x, y):
where M is the number of pixels in the neighborhood S.
This is useful when only one version of the image is available.
If this operation is performed over a 3 x 3 neighborhood, we have