| 摘要 |
PROBLEM TO BE SOLVED: To properly set a binarization threshold so as to satisfactortly separate a background part from a part of characters, etc., in binarizing picture data obtained by reading an original. SOLUTION: The histogram of the picture data is obtained and the gradation value of a peak part where frequency is the highest in this histogram is obtained as mwm(Mid of White Mountain). The gradation value of the intersection of the histogram and a threshold sll on the side of a Low gradation with mwm as reference is calculated as wlwm(White Limit of White Mountain). Then, a difference value between mwm and wlwm is obtained, this is added with mwm to obtain blwm(Black Level of White Mountain), and this is set to be a reference binarization threshold. A binarization threshold correcting table is obtained by correcting a table for obtaining the binarization threshold based on the reference binarization threshold. The reference binarization threshold is obtained by reading an original and a calculated binarization threshold is obtained by referring to the table, thereby the picture data are binarized to be printed.
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