| 摘要 |
PROBLEM TO BE SOLVED: To attain accurate binarization by eliminating an image data part to be extracted thereby calculating a threshold following to the base density of an original or the like. SOLUTION: An average density of a notice pixel (N) is calculated (STEP 2) on the basis of image data of the notice pixel (N) to be binarized and its peripheral pixels, the difference between a threshold of a just preceding pixel (N-1) of the notice pixel (N) to be binarized and the average density is obtained as a change value (STEP 3), a following value denoting the degree of change in the threshold of the notice pixel (N) is calculated (STEP 4) on the basis of this change value and the following value and the average density are summed to obtain the threshold in the notice pixel (N) (STEP 5).
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