| 摘要 |
A method of transforming an image of a document into a binary signal. Each pixel of the document is read and expressed in terms of a signal having one of eight levels. This signal is compared with the signals of the immediately adjacent pixels. A new level is assigned to the given pixel according to the formula D'=3D0-D1-D2 . . . -DN. This new level is then compared to a reference level, and the signal is binary-coded accordingly.
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