Polynomial based multi-level screening

Details Polynomial based multi-level screening Polynomial based multi-level screening

2005-09-06

2005-09-06

Lee, Thomas D. (Department: 2624)

Facsimile and static presentation processing

Static presentation processing

Attribute control

C358S519000

Reexamination Certificate

active

06940619

ABSTRACT:
This invention is a computer implemented method of approximating a gray scale tone with a more limited range image producer. One of a plurality of tone curves is associated with each pixel of a screening matrix. The plural tone curves are approximated by a polynomial and the polynominal coefficients are determined. The polynomial coefficients are stored in a look-up table. Each pixel of an image is mapped to a corresponding pixel of the screening matrix. For each pixel the corresponding polynomial coefficients approximating the tone curve are recalled and used to compute a pixel output value from a pixel input value. The polynomial is preferrably of the third degree polynomial and in a form easily computed using a digital signal processor with a hardware multiplier and arithmetic logic unit. Screening in this manner requires less memory storing the screening data than the prior art pure look-up table screening.

REFERENCES:
patent: 5724627 (1998-03-01), Okuno
patent: 6064396 (2000-05-01), Ouchi
patent: 6160643 (2000-12-01), Deschuytere et al.
patent: 0 634 862 (1995-01-01), None
patent: 0 899 943 (1999-03-01), None
patent: 08 125865 (1996-05-01), None

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