Mixed matrix image processing for rendering halftone images with

Details Mixed matrix image processing for rendering halftone images with Mixed matrix image processing for rendering halftone images with

1991-11-13

1993-03-30

Brinich, Stephen

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358448, 358455, H04N 140

Patent

active

051989107

ABSTRACT:
An image processing system renders halftone images with an increased number of gray level steps without increasing the number of sub-elements in the halftone cells. A document copying apparatus which generates a plurality of electrical image signals of successive picture elements of an original document compares input image signals representing low optical density picture elements of the original document to a series of threshold values selected from a two dimensional matrix halftone cell in which an output signal density pattern grows in a low spacial frequency manner; compares input image signals representing high optical density picture elements to a series of threshold values selected from a two dimensional matrix halftone cell in which an output signal density pattern grows in a high spacial frequency manner; and compares input image signals representing mid-optical density picture elements to a series of threshold values selected from the first or the second halftone cells according to the optical density of the picture element.

REFERENCES:
patent: 3922484 (1975-11-01), Keller
patent: 4449150 (1984-05-01), Kato
patent: 4866534 (1989-09-01), Tada
IEEE Transactions on Communications, vol. Com-29, No. 12, Dec. 1981, "A Survey of Electronic Techniques for Pictorial Image Reproduction", J. C. Stoffel and J. F. Moreland, pp. 1898-1925.
The Fourth International Congress on Advances in Non-Impact Printing Technologies, Peter A. Torpy, Mar. 20-25, 1988, pp. 380-383 "Obtaining More Gray Levels in a Halftoned Reproduction by Use of Pixel Overlap".
RCA Review-vol. 31, No. 3, Sep.1970, Princeton (U.S.) pp. 517-533; R. J. Klensch et al.; "Electronically Generated Halftone Pictures".
IEEE Transactions on Communications; vol. Com 29, No. 12; Dec. 1981; pp. 1898-1925; J. C. Stoffel et al.; "A Survey of Electronic Techniques for Pictorial Image Reproduction".

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