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Improvement of Digital Typeface Printing

IP.com Disclosure Number: IPCOM000063027D
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18

Publishing Venue

IBM

Related People

Authors:
Colby, RS [+details]

Abstract

Digital generation of typefaces for display or printing can present a "stair-step" or jagged appearance on diagonal character edges, and to a lesser extent on curves as well. Examples of the extreme cases can be provided by wire matrix printers with as few as 7 picture elements (pels) in a character height, and by photocomposers with several thousand. Typical high speed electrophotographic printers have a resolution or pel density of the order of 240 per inch. While stair-steps or "jaggies" are not a significant problem, a useful degree of refinement can be obtained. This can be done by adjusting certain pels to intermediate (gray) levels between white and black. Some approaches to determining which pels should be gray rely on pre-encoding each pel with level information.