Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1984-08-20
1986-06-03
Groody, James J.
Facsimile and static presentation processing
Facsimile
Recording apparatus
382 50, H04N 140
Patent
active
045933251
ABSTRACT:
An adaptive threshold for processing grayscale image data obtained by scanning a document to be duplicated is set by initially dividing the data into data groups representative of selected pixels of the document. A background grayscale value and a print grayscale value are determined for each data group with the difference between the two defining a contrast grayscale value. An estimated threshold is calculated by adding 0.4 of the contrast to the background. An average threshold is also determined for the area of each data group by averaging the thresholds for contiguous data groups for which thresholds have been established. The adaptive threshold is determined for each data group by setting the adaptive threshold to the average threshold +1 if the estimated threshold exceeds the average threshold; to the average threshold -1 if the estimated threshold is less than the average threshold; and, to the average threshold otherwise. The grayscale image data for each data group is compared to its corresponding adaptive threshold to generate binary data which drives a printer to substantially duplicate the document.
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Bobick Thomas W.
Kannapell Henry N.
Coles Edward L.
Groody James J.
The Mead Corporation
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