Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1991-11-27
1993-12-07
Brinich, Stephen
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358445, H04N 140
Patent
active
052687740
ABSTRACT:
Gray pixel values, where the value of the pixel has one of a relatively large number of input levels, are directed through an error diffusion quantization process, for the conversion to one of a relatively small number of values. Each pixel of the gray level data is modified by a correspondingly weighted error correction term or terms from previously processed pixels, generating a modified pixel value. This modified pixel value is compared to a threshold value, the threshold value determined adaptively, based on 1) a dither pattern, having a dynamic range greater than 1, and 2) the value of the pixel to be thresholded, and optionally on its predetermined neighborhood, multiplied by a value representing an edge enhancement factor. The difference value between the modified pixel value and the output pixel value is distributed in accordance with a weighted distribution scheme to a set of neighboring unprocessed pixels, increasing or decreasing the gray values of such pixels.
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Brinich Stephen
Costello Mark
Xerox Corporation
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