Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1994-07-01
1996-09-17
Bayerl, Raymond J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358456, G06K 100
Patent
active
055577091
ABSTRACT:
An existing void-and-cluster method for generating dither arrays for halftoning grayscale images on binary printing devices is improved by including additional steps which both homogenize the starting pattern used in the void-and-cluster method and correct the starting pattern for the effects of oversized dots generated by the printing devices. More particularly, a constant gray starting pattern is first subjected to an error diffusion halftoning process before void and cluster processing to produce a starting binary pattern as a more homogeneous starting point. In addition, after the starting binary pattern has been created, it can be modified to take into account that most printers print "oversized dots" in order to avoid white areas between dots. In particular, from the starting binary pattern, a starting gray pattern is created which uses oversized dot information to assign grayscale values to the "0" pixels surrounding a "1" pixel. Then cluster-finding and void-finding filters are used on both the starting binary pattern and the starting gray pattern to locate "clusters" and "voids". Pixels are transferred from the clusters to the voids to homogenize the arrays and generate an initial binary pattern and an initial gray pattern. The initial binary pattern and the initial gray pattern are then used to assign threshold values to the dither array.
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Bayerl Raymond J.
Garcia Gabriel I.
Janofsky Eric B.
Seiko Epson Corporation
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