Patent ID: 7796305

Claim:
An image scanning apparatus comprising: a gain unit configured to convert image information into a voltage and apply a desired gain to the voltage during a scanning operation; an analog-to-digital conversion unit configured to digitize the image information to generate a digital image; a first shading correction unit configured to perform shading correction to the digital image by using a first coefficient correlated to a white reference value to yield a first corrected image; a second shading correction unit configured to perform shading correction to the digital image by using a second coefficient correlated to a corrected trace to yield a second corrected image having a luminance higher than the white reference value; an image processing unit configured to perform image processing to the first corrected image to generate first digital image information; a correction detecting unit configured to detect the corrected trace from the second corrected image to generate second digital image information which is detection information concerning the corrected trace; and a synthesizing unit configured to synthesize the first and second digital image information together to generate third digital image information in which the detection information concerning the corrected trace is embedded in the first digital image information, wherein the correction detecting unit generates the second digital image information by considering an area having a smaller number of continuous pixels on a trail of detection of a closed curve, performed by using the image, than a predetermined threshold as a non-correction-fluid portion, and by considering an area having a larger continuous amount on the trail as a correction-fluid-portion.