Patent ID: 6961151

Claim:
An image reading-out apparatus for exposing and scanning an original document to read out an image on said original document and thereby obtaining image data, comprising: a background level detecting circuit configured to detect a background level of said original document from said image data; an analog-to-digital converter configured to remove an influence due to a color of said background level on said original document from said image data and configured to perform an analog-to-digital conversion of said image data in accordance with said detected background level; and a black-shading compensation circuit configured to perform a black-shading compensation of said image data after said analog-to-digital conversion, wherein said black-shading compensation circuit comprises: plural black level value calculating circuits configured to respectively obtain, per each line, black level values employed for said black-shading compensation from said image data by use of respective different calculation members; a selection circuit configured to select and output one black level value among the black level values outputted by said plural black level value calculating circuits; and a subtracter configured to subtract said selected black level value from said image data after performing said analog-to-digital conversion and said black-shading compensation.