Apparatus for converting image signal representing image having

Details Apparatus for converting image signal representing image having Apparatus for converting image signal representing image having

1993-06-14

1995-04-25

Rogers, Scott A.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358458, 358464, H04N 140

Patent

active

054104181

ABSTRACT:
An apparatus for converting an image signal representing an image having gradation includes a first density histogram generator. The first density histogram generator generates a first density histogram based on a first image signal which is obtained by reading a data read region. Of peak portions formed in the first density histogram, the density rank value of a peak portion which satisfies a predetermined condition is detected. A pixel-to-be-removed detector determines pixels-to-be-removed whose average densities are included in a pixel removal density range which corresponds to the detected peak portion density rank value. A second density histogram is generated from the pixels remaining after the removal of the pixels-to-be-removed. Based on the second density histogram, a cumulative density histogram is generated to thereby find a highlight point and a shadow point through which a gradation curve passes. Then, the gradation curve is established and an image processing part converts the first image signal into a second image signal in accordance with the established gradation curve.

REFERENCES:
patent: 4792978 (1988-02-01), Nomura et al.
patent: 4975970 (1990-12-01), Zettel et al.
patent: 4984071 (1991-01-01), Yonezawa
patent: 5280367 (1994-01-01), Zuniga
Patent Abstracts of Japan, vol. 13, No. 429 (E-823), Dec. 17, 1987 & JP-A-1160167, Fuji Photo Film, Jun. 23, 1989.

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