IMAGE CORRECTING DEVICE, OVERHEAD TYPE IMAGE READING DEVICE, AND IMAGE CORRECTING METHOD AND PROGRAM

PROBLEM TO BE SOLVED: To remove horizontal stripes of an image due to a flicker by a simple structure.SOLUTION: An image processing portion 31 of an overhead type image reading device 1 includes: an image processing memory 33 obtaining reading image data generated by moving an optical unit 10 in a sub-scanning direction to read a document 70 while the document 70 is irradiated with environment light; a first determining portion 41 for selecting a correction filter correcting a target pixel 72 on the basis of the lightness or brightness components of the pixel 71 in a determination filter including the target pixel 72, of the obtained reading image data; and an image processing circuit 34 for correcting gradation data of the target pixel 72 on the basis of the correction filter selected by the first determining portion 41. The determination filter has a plurality of determination filters having a different number of pixels 71 to be used in the sub-scanning direction.