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Proceedings Paper

A Robust Two-Dimensional Adaptive Thresholder For Bilevel Digital Display And Electronic Printing
Author(s): To R. Hsing; James C. Stoffel
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Paper Abstract

In the application of bilevel digital display and electronic printing, threshold setting is used to get binary images from optical scanning digitizers.' Such images can be simply obtained by using a fixed threshold to a raw continuous tone image. However, due to (1) a wide range of color backgrounds, (2) wide density variations of the printed information, and (3) the shading effect caused by imaging optics, the use of adaptive threshold setting is obviously needed for obtaining high quality displays and hard copies. This paper will describe a robust two-dimensional adaptive thresholder for obtaining valid bilevel images. It is basically a memory type algorithm which can dynamically update the black and white reference level to optimize a local threshold function. The local information in both fast scan and slow scan directions has been considered for threshold calculation. The algorithm and its associated hardware functional block diagram will be described. The experimental results are presented to describe the procedures. The robust algorithm below has shown an adaptability of 0.15 ▵D for density varied text information. A high contrast 35 μm line or low contrast 70 μm to 500 μm line can be detected by the algorithm. Both objective evaluations and subjective pictorial results have indicated promising usage of this algorithm for multicolor inputs or colored background documents.

Paper Details

Date Published: 9 January 1984
PDF: 7 pages
Proc. SPIE 0432, Applications of Digital Image Processing VI, (9 January 1984); doi: 10.1117/12.936648
Show Author Affiliations
To R. Hsing, GTE Laboratories Incorporated (United States)
James C. Stoffel, Xerox Corporation (United States)

Published in SPIE Proceedings Vol. 0432:
Applications of Digital Image Processing VI
Andrew G. Tescher, Editor(s)

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