| 摘要 |
PURPOSE:To convert a character, a code or the like into a clear binary picture independently of the density of ink or a base color by detecting the whitest value and the blackest value in each small area on the surface of a document to set up the threshold of binary-coding, and binary-coding a multilevel picture signal on the basis of said threshold. CONSTITUTION:A multivalued picture signal formed by scanning a pattern such as a character and a code entered on a document 10 by a scanning part 40 is stored in a temporaty storage means 60. A multivalued picture signal corresponding to an area divided into a required range by a masking part 70 is read out from the means 60 to the masking part 70 and the whitest value and the blackest value out of the multivalued picture signal stored in the masking part 70 are detected by a whitest value detecting part 80 and a blackest value detecting part 90. A threshold determination part 100 determines a threshold for a signal positioned on the center of areas divided on the basis of the whitest value and blackest value signals. A binary coding circuit part 110 compares the threshold with the signal positioned on the center of the divided areas to form a binary picture signal.
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