Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1992-06-29
1994-03-01
Coles, Sr., Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358457, 358460, H04N 140
Patent
active
052913112
ABSTRACT:
Apparatus and a method for generating a multi-level halftone image (104) from a digitally sampled continuous tone image (101). The apparatus includes a control circuit (140), a preference matrix (150) having as its matrix elements addresses of a plurality of look-up tables (160) and a plurality of look-up tables (160) in the form of a look-up table stack (155). Generally, the control circuit (140) instructs the preference matrix (150) to select a look-up table (160) from the look-up table stack (155) in a pre-defined manner. The selected table (160) is used to convert an intensity value (102) into a multi-level pixel value (106) in the halftone image (104). To accomplish the conversion, each look-up table (160) contains a quantized one-dimensional transfer function (165') having as an input the magnitude of the intensity value (102). The magnitude is mapped into an output level by the transfer function as one of a plurality of available levels. The output level is assigned a pixel location in a halftone cell (103). The look-up table selection is repeated for each element of the preference matrix (150) and the magnitude of each intensity value (102) is mapped into the halftone cell (103) to generate a multi-level halftone image (104).
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Coles Sr. Edward L.
Eastman Kodak Company
Holloway William W.
Michaelson Peter L.
Moser Raymond R.
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