Browse Prior Art Database

Edge Enhanced Digital Halftone

IP.com Disclosure Number: IPCOM000085915D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Machol, GK: AUTHOR

Abstract

Digital halftone techniques, which render gray scale images by using only binary (black/white) picture elements, have limited spatial resolution. The process tends to obliterate fine detail and to "fuzz" the edges of text and graphic data. In some applications where digital halftoning is desired, there may be a need to counteract this loss of information.

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Edge Enhanced Digital Halftone

Digital halftone techniques, which render gray scale images by using only binary (black/white) picture elements, have limited spatial resolution. The process tends to obliterate fine detail and to "fuzz" the edges of text and graphic data. In some applications where digital halftoning is desired, there may be a need to counteract this loss of information.

A method is described for improving the capability of digital half tone techniques to portray regions of fine detail. Further, this method makes it possible to convert, to halftone, image data containing text and/or other graphic portions without deterioration of those portions, as usually occurs when such data is transformed into digital halftone.

The circuit shown merges the halftone data with edge information in order to bring out the fine detail. Each incoming picture element (pel) 10 (an analog or digital gray scale value) is converted to a binary pel value 13 (white or black) according to some digital halftone algorithm by halftone generator 12.

The algorithm may require information about the surrounding pels 14. Concurrently, a determination is made as to whether or not the pel 10 is on an edge by edge detector 14; i.e., on either side of a region of sharp contrast. If it is found that the pel 10 is not on an edge (line 18 negative), then the binary value of the halftone generator 12 is delivered unchanged to the output 24 via AND 21 and OR 22. Otherwise, if the pel 10 is on the dark side of the edge, the output pel is set to black; if the pel is found to be on the light side of the edge (line 19 negative), the output pel is set to white.

The edge threshold is, in general, a functio...