Image processing apparatus for estimating halftone images from b

Details Image processing apparatus for estimating halftone images from b Image processing apparatus for estimating halftone images from b

1989-12-19

1993-12-14

Herndon, Heather R.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

395132, 358298, G06F 1562

Patent

active

052710955

ABSTRACT:
An image processing apparatus for receiving digital image data including bilevel images such as character and line draw images and pseudo halftone images such as dither image and error diffusion image and for estimating a halftone image. The apparatus comprises a dither image detector for detecting the presence/absence of a cycle of the image from a peak interval of auto-correlation values of the respective lines of the image data and detecting the pattern when the cycle is present, a density variation detector for detecting a variation in density of the image of each cycle, a pseudo halftone image detector for detecting a degree of variance of pixels from a dot pattern of a pixel region having a predetermined range, a selector for selecting an aperture having a size equal to the detected cycle when the input image has a cycle and the variation in density is small, an aperture having a size smaller than the detected cycle when the variation in density is large, and an aperture having a size corresponding to the degree of variance of pixels when the cycle is not detected. The apparatus further comprises a halftone image estimating circuit for averaging the digital image data by the aperture having the selected size.

REFERENCES:
patent: 4649500 (1987-03-01), Yamada et al.
patent: 4675831 (1987-06-01), Ito et al.
patent: 4866534 (1989-09-01), Tada
patent: 4920501 (1990-04-01), Sullivan et al.
patent: 5045880 (1991-09-01), Evanitsky et al.

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