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The IIR Gaussian Blur plug-in acts on each pixel of the activ layer or selection, setting its Value to the average of all pixel Values present in a radius defined in the dialog. A higher Value will produce a higher amount of blur. The blur can be set to act in one direction more than the other by clicking the Chain Button so that it is broken, and altering the radii. It is well adapted to scans and photos with smooth color transitions.