37.4: Filter Design for Void-and-Cluster Dither Arrays

The Void-and-Cluster method for producing ordered dither arrays is powerful in its simplicity and flexibility. Central to the method is the voidand cluster-finding filter. This paper explores the use of a gaussian filter, and in particular, the effect of the gaussian parameter σ on image quality. Excellent isotropic bluenoise dithering can be achieved with a σ between 1.0 and 1.5 with relatively small period arrays. Smaller values of σ tend to leave slightly inhomogeneous voids, while larger values tend to form regularly spaced clusters.