Patent ID: 8576466

Claim:
An image processing apparatus comprising: a component configured to read a document with a reading unit; a component configured to store a read value; a component configured to convert the read value in a device-dependent color space into a value in a device-independent color space using a color conversion table; a component configured to store a target value of correction used to correct the color conversion table; a component configured to store a correction lookup table used to input a value in the device-independent color space converted from a value in the device-dependent color space by the color conversion table and to convert the input value into an output value in the device-independent color space, wherein the correction lookup table is different from the color conversion table; a component configured to modify a value in the device-independent color space of the correction lookup table using a difference value between the stored read value and the stored target value, wherein the correction lookup table is a lookup table used to convert an input value in the device-independent color space into an output value in the device-independent color space; and a component configured to update the color conversion table using the modified correction lookup table, wherein the correction lookup table is a lookup table used to convert an input value in the device-independent color space into an output value in the device-independent color space, wherein the document comprises patches, the number of the patches is smaller than the number of lattice points of the correction lookup table, and wherein the read value and the target value are obtained by reading the patches by the reading unit and wherein the correction lookup table is a lookup table used to convert an input value in the device-independent color space into an output value in the device-independent color space.