| 摘要 |
PROBLEM TO BE SOLVED: To make appropriately settable the reference signal value of a gray level transformation curve by excluding a high-luminance pixel from an effective pixel at the time of histogram preparation and finding the reference signal value from that histogram. SOLUTION: A signal value for every RGB of a pixel is inputted and compared with the threshold of lightness (S301 and S302). Only the pixel satisfying the conductions of comparison is inputted, the maximum value Max and minimum value Min of respective signal values are calculated, Max-Min is calculated and the maximum value of a difference between mutually different color components is found (S303 and S304). The maximum value of the difference between the mutually different color components is compared with a threshold and when the maximum value is greater than the threshold, that pixel is not regarded as an effective pixel and is not counted to the histogram. When the maximum value is smaller than the threshold, that pixel is regarded as an effective value and the signal value is counted to the histogram (S305 and S306). It is judged the comparison has been performed concerning all the pixels and at the time point of end of all the pixels, histogram preparing processing of the effective pixel is finished (S307 and S309).
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