Image processing apparatus and image processing method that correct color conversion table used when reading document
AssigneeCanon Kabushiki Kaisha
InventorAsako Hashizume
Life of this patent
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Abstract
Conventionally, it is not possible to evenly correct a color conversion table of a reading device in the entire color region even with a limited number of patches. In order to correct a color conversion table, a color conversion table from a device-independent color space into a device-independent color space is newly stored. A shift in read data between devices is reflected in a correction 3D-LUT and a color conversion table is corrected using the correction 3D-LUT. Thereby, it is possible to correct the entire color region with a smaller number of pieces of data and with less time and effort than when a color conversion table is newly recreated.
Claims15
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.
An image processing method in an image processing apparatus including 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, and a component configured to store a target value of correction used to correct the color conversion table, the method comprising the steps of:
- storing 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;
- modifying 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
- updating 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.
A non-transitory computer readable recording medium having a program that causes a computer to execute an image processing method in an image processing apparatus including 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, and a component configured to store a target value of correction used to correct the color conversion table,
- conversion of the read value from device dependent color space into device independent color space,
- the image processing method comprising the steps of:
- storing 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;
- modifying 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
- updating 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.
Dependencies are inferred from the claim text.