Patent ID: 8675258

Claim:
An image reader comprising: a scanning unit that scans a document by a contact image sensor system; a white member that is arranged to face a scanning surface of the scanning unit; a gap variable unit that moves at least one of the scanning unit and the white member to change a size of a gap that is a space between the scanning surface of the scanning unit and the white member; a reference data ratio storage unit that stores a reference data ratio as a ratio between first reference data acquired by scanning a surface of the white member by the scanning unit in a state where the size of the gap is substantially equal to a size of the gap when the document is scanned and second reference data acquired by scanning the surface of the white member by the scanning unit in a state where the size of the gap is smaller than the size of the gap when the document is scanned; a shading data generation unit that causes the scanning unit to scan the surface of the white member in the state where the size of the gap is substantially equal to the size of the gap when the document is scanned to acquire third reference data and multiplies the third reference data by the reference data ratio to generate shading data; and a shading correction unit that corrects image data of the document scanned by the scanning unit using the shading data.