| 摘要 |
PROBLEM TO BE SOLVED: To correct the luminance distribution of the image data of a document to a prescribed level. SOLUTION: The image data of the document 1 are read by a CCD(charge coupled device) sensor 11 and stored in an image memory 12. A frequency distribution generating section 13 generates the luminance frequency distribution of pixels based on the image data in the image memory 12 and stores it in a frequency distribution memory 14. A document density detecting section 15 detects a peak near the white level in the frequency distribution as the density of the ground color of the document. A luminance correcting section 16 determines a correction value based on the ratio between the luminance of the pixels in the image memory 12 and the density of the ground color in reference to a correction value table 17. The determined correction value is multiplied by the predetermined reference luminance to output corrected image data DATA.
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