9 January 1984 A Robust Two-Dimensional Adaptive Thresholder For Bilevel Digital Display And Electronic Printing
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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.
© (1984) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
To R. Hsing and James C. Stoffel "A Robust Two-Dimensional Adaptive Thresholder For Bilevel Digital Display And Electronic Printing", Proc. SPIE 0432, Applications of Digital Image Processing VI, (9 January 1984); doi: 10.1117/12.936648; https://doi.org/10.1117/12.936648
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