Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1992-07-13
1995-08-15
Ip, Paul
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358465, 358466, 358458, H04N 140
Patent
active
054424615
ABSTRACT:
A halftone screen, at a desired screen angle and ruling, is generated by concatenating strips of an ideal angled screen pattern. Artifacts are reduced by aligning the vertical boundaries between adjacent strips. In one embodiment, a screen pattern is generated by storing a plurality of double width strips from an ideal angled screen pattern, and concatenating a sequence comprising a portion of each double width strip in a selected order. Regardless of the choice of starting point in the strip for each successive scan line, a sufficient portion of the double width strip is clocked out until the edge of the strip aligns with the strip above it. In a second embodiment, strips of a rational angled screen are concatenated to approximate an irrational angled screen. Errors which accumulate with each successive pixel are corrected by occasionally jumping to a new point in the strip. The vertical boundaries of successive horizontal strips aligned by placing the occasional jumps at the same point for each successive scan line. In a third embodiment, a screen pattern is generated by assembling fixed width strip portions, selected from a stored oversized strip of the ideal angled screen pattern. Since the width of all the strips in the screen is fixed, the vertical boundaries between adjacent strips are aligned.
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Ip Paul
Jacobson Allan
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