| 摘要 |
PROBLEM TO BE SOLVED: To provide an image reader that can correct shading with high accuracy even when no dust or dirt exists at a position of a reference white board equivalent to a position of a target pixel. SOLUTION: The image reader has a maximum value detection circuit 19 that calculates a maximum value among a data value of a target pixel of an image sensor (CCD) 15 and data values of surrounding pixels of the target pixel among image data by one line obtained by the image sensor 15 that reads a white board read, a differential circuit 20 that calculates a difference between the maximum value and the data value of the target pixel, a comparator circuit 22 that compares the difference with a prescribed value, and a shading correction circuit 24 that uses the maximum value for a reference white level of the target pixel when the difference is greater than a specified value on the basis of the comparison result by the comparator circuit 22 or uses the data value of the target pixel as it is for the reference white level of the target pixel when the difference is the specified value or below and uses the reference white level to conduct shading correction.
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