| 摘要 |
An image processing system for converting gray level, digital, pixel information into binary data. Pixels with digital values close to the threshold value are further processed to determine the binary value to be specified for that pixel. In such cases, the adjacent horizontal pixel is tested and, if that test is inconclusive, the adjacent vertical pixel is tested. Depending upon the tests of whether the adjacent pixels were also close to the threshold value, the current pixel value is assigned the opposite value as the previous adjacent pixel. This has the effect of specifying, for transition areas at the boundaries of text characters and graphic lines, alternating pixels which produce a serrated edge along the borders of the character or line. These edges are of high spatial frequency and are substantially undetectable under ordinary circumstances by an observer. These edges are also smoothed in the printing process by the fusing of the toner to the output medium. The invention is also applicable to adding alternating pixel areas to larger areas defined by digital values close to a predetermined threshold value, and enhances the information stored by binary bits for continuous-tone and half-tone pictorial images.
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