Method and apparatus for producing halftone image with threshold

Details Method and apparatus for producing halftone image with threshold Method and apparatus for producing halftone image with threshold

1995-02-01

1998-09-29

Lee, Thomas D.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358455, 358456, 358465, 382237, H04N 140

Patent

active

058152865

ABSTRACT:
A threshold matrix is divided into a plurality of sub-matrices Tij of an equal size. The difference between a plurality of threshold data included in each sub-matrix Tij is set to a specific value while the plurality of threshold data are arranged at random in each sub-matrix Tij. In case that each sub-matrix is a 2.times.2 arrangement, there are eight diagonal patterns where two relatively small threshold data are arranged diagonally while two relatively large threshold data are also arranged diagonally. A threshold matrix having the sufficiently high spatial frequency and allowing smooth tone reproduction can be prepared by selecting one of the eight diagonal patterns at random. A plurality of threshold matrices for respective color separations thus prepared will reduce the graininess and muddiness of colors in a reproduced color image. A plurality of threshold matrices can be produced from one original threshold matrix by extracting part of the threshold matrix.

REFERENCES:
patent: 4736254 (1988-04-01), Kotera et al.
patent: 5107349 (1992-04-01), Ng
patent: 5150428 (1992-09-01), Leone et al.
patent: 5315405 (1994-05-01), Okuwaki
patent: 5477305 (1995-12-01), Parker
patent: 5530559 (1996-06-01), Sato
Optical Engineering, Jul. 1985, vol. 24, No. 4, M. F. Carlsohn et al., pp. 655-662.

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