| 摘要 |
PROBLEM TO BE SOLVED: To improve readability of a low contrast part in an image thresholding method for thresholding an analog or multi-gradation digital image to be processed by level-discriminating it according to a threshold. SOLUTION: A concentration histogram of each component of R, and B of a picture and maximum values Rmax, Gmax, and Bmax and minimum Rmin, Gmin, and Bmin of concentration histogram distribution of each R, G, and B are calculated (s8), and the concentration histogram distribution is extended so that the values of both edges of each data value area can be obtained (s9-s11). Thus, correction of brightenss and the correction of contrast shortage and the correction of color tone can be operated. As a result, satisfactory binary pictures suitable for contents judgment can be obtained. Also, a contrast and the color tone can be simultaneously corrected, and processing speed can be improved.
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