Method and apparatus for gray screening

Details Method and apparatus for gray screening Method and apparatus for gray screening

1995-12-07

1998-03-17

Rogers, Scott A.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358456, 358465, H04N 140

Patent

active

057296634

ABSTRACT:
The present invention is a method and apparatus for generating N-bit per pixel output signals in response to M-bit per pixel image input signals, where M is greater than N. The invention employs a halftone cell threshold memory that stores a single threshold for each cell element. During real-time processing of the video image signals, multiple thresholds are calculated based upon the stored thresholds, and the image signals are compared to the thresholds. The threshold calculation process is simplified by using equally spaced constants and any desired variation from the resulting equally spaced thresholds is accomplished through a remapping of the video image signals using a look-up table. The output of the plurality of comparisons carried out for each halftone cell element is then encoded to produce a digital gray-scale output signal.

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