Patent ID: 8031381

Claim:
An image reading apparatus comprising: an image reading unit adapted to read an RGB image of an original being conveyed; a background member, comprising a first portion having a white color and a second portion having a different color from the white color, each of which is used to form a background color in the RGB image of the original read by said image reading unit; a background color changing unit adapted to position said background member such that one of the first portion and the second portion is disposed opposite said image reading unit a determining unit adapted to determine a correction coefficient for image processing to be performed on the RGB image, depending on which portion of said background member is disposed opposite said image reading unit and regardless of the original, wherein the correction coefficient and values of the RGB image uniquely define the image processing; and wherein said image processing is performed using the following expression R ′ = R + γ R × ( R × G × B ) 255 3 G ′ = G + γ G × ( R × G × B ) 255 3 B ′ = B + γ B × ( R × G × B ) 255 3 for calculating an output value (R′, G′, B′) for an input value (R, G, B) based on the correction coefficient (γ R , γ G , γ B ).