Image processing apparatus and method, and profile generating method

• US 6,859,551 B2
• Filed: 06/19/2002
• Issued: 02/22/2005
• Est. Priority Date: 07/24/1998
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ohga, Manabu
• Primary Examiner(s): Ahmed, Samir
• Assistant Examiner(s): BHATNAGAR, ANAND P
• Application Number:
  US10/173,636
• Publication Number:
  US 20030016862A1
• Time in Patent Office: 979 Days
• Field of Search: 345/590, 345/591, 345/603, 345/604, 382/162, 382/167, 358/1.9, 358/518, 358/519, 358/520, 358/521, 358/522, 358/523
• US Class Current: 382/167
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut
• CPC Class Codes: H04N 1/6086 by scene illuminant, i.e. conditions at the time of picture capture, e.g. flash, optical filter used, evening, cloud, daylight, artificial lighting, white point measurement, colour temperature
• CPC Class Codes: H04N 1/6088 by viewing conditions, i.e. conditions at picture output

Abstract

If gamut mapping (hue restoration) defined by one Lab color space is applied in color matching under different reference white points, the human vision perceives the hue as inconsistent. In view of this, input data which is dependent on a color space of an input device is converted by the conversion LUT 11 to color space data which is independent of any devices, based on a viewing condition at the time of viewing an input original. The data is converted to data in the human color perception space by the forward converter 12, then subjected to gamut mapping, and converted back to data in the color space independent of any devices by the inverse converter 15, based on a viewing condition at the time of viewing an output original. Then, the data is converted to output data in a color space which is dependent on an output device by the conversion LUT 16.

Claims

1. An image processing method of performing a color matching process, said method comprising:

a setting step of setting a mode for color gamut mapping from a plurality of modes, wherein the plurality of modes include a relative mode for performing relative color matching and an absolute mode for performing an absolute color matching;

a first conversion step of converting input data, which is dependent on a color space of an input device, to first data, which is color space data that is independent of any device;

a second conversion step of converting the first data to second data in a color perception space, which corresponds to the set mode and is independent of a viewing condition, wherein said second conversion step performs a forward conversion of a color appearance model, based on the set mode and an input viewing condition, on the first data;

a first calculation step of calculating third data by performing the color gamut mapping, which corresponds to a color reproduction range of an output device, on the second data converted in accordance with the set mode;

a second calculation step of calculating fourth data in a device independent color space by performing an inverse conversion of the color appearance model, based on the set mode and an output viewing condition; and

a third conversion step of converting the fourth data into output color space data which is dependent on the output device,

wherein the color perception space is a relative color perception space when the relative mode is set, and an absolute color perception space when the absolute mode is set.

2. A method according to claim 1, wherein the relative color perception space is relative to a reference white point of an ambient light, and the absolute color perception space size is changed in accordance with an illumination level.

3. A method according to claim 1, wherein compression data, used in the color gamut mapping of the second data, and conversion data, used in said third conversion step, are obtained from a profile of the output device.

4. A method according to claim 1, wherein the mode is automatically set based on information of a profile of the input device.

7. A method according to claim 1, wherein said setting step includes setting the mode in accordance with a user'"'"'s manual instruction or header information of a profile from a source side.

5. A computer program product storing computer program codes for executing an image processing method of performing color matching process, said program comprising:

code for a setting step of setting a mode for color gamut mapping from a plurality of modes, wherein the plurality of modes include a relative mode for performing a relative color matching and an absolute mode for performing an absolute color matching;

code for a first conversion step of converting input data, which is dependent on a color space of an input device, to first data, which is color space data that is independent of any device;

code for a second conversion step of converting the first data to second data in a color perception space, which corresponds to the set mode and is independent of a viewing condition, wherein said second conversion step performs a forward conversion of a color appearance model, based on the set mode and an input viewing condition, on the first data;

code for a first calculation step of calculating third data by performing the color gamut mapping, which corresponds to a color reproduction range of an output device, on the second data converted in accordance with the set mode;

code for a second calculation step of calculating fourth data in a device independent color space by performing an inverse conversion of the color appearance model, based on the set mode and an output viewing condition; and

code for a third conversion step of converting the fourth data into output color space data which is dependent on the output device,

wherein the color perception space is a relative color perception space when the relative mode is set, and an absolute color perception space when the absolute mode is set.

8. A computer program product according to claim 5, wherein said setting step includes setting the mode in accordance with a user'"'"'s manual instruction or header information of a profile from a source side.

6. An image processing apparatus for performing color matching process, comprising:

a setting section, arranged to set a mode for color gamut mapping from a plurality of modes, wherein the plurality of modes include a relative mode for performing a relative color matching and an absolute mode for performing an absolute color matching;

a first converter, arranged to convert input data, which is dependent on a color space of an input device, to first data, which is color space data that is independent of any device;

a second converter, arranged to convert the first data to second data in a color perception space, which corresponds to the set mode and is independent of a viewing condition, wherein conversion of the first data to the second data is accomplished by performing a forward conversion of a color appearance model, based on the set mode and an input viewing condition, on the first data;

a first calculator, arranged to calculate third data by performing the color gamut mapping, which corresponds to a color reproduction range of an output device, on the second data converted in accordance with the set mode;

a second calculator, arranged to calculate fourth data in a device independent color space by performing an inverse conversion of the color appearance model, based on the set mode and an output viewing condition; and

a third converter, arranged to convert the fourth data into output color space data which is dependent on the output device,

wherein the color perception space is a relative color perception space when the relative mode is set, and an absolute color perception space when the absolute mode is set.

9. An apparatus according to claim 6, wherein said setting section includes setting the mode in accordance with a user'"'"'s manual instruction or header information of a profile from a source side.

10. An image processing method of performing a color matching process, said image processing method comprising:

a setting step of setting a mode for color gamut mapping from a plurality of modes, wherein the plurality of modes include a relative mode for performing a relative color matching and an absolute mode for performing an absolute color matching;

a conversion step of converting first data to second data in a color perception space which corresponds to the set mode and is independent of a viewing condition, wherein said conversion step performs a forward conversion of a color appearance model, based on the set mode and an input viewing condition, on the first data;

a first calculation step of calculating third data by performing the color gamut mapping, which corresponds to a color reproduction range of an output device, on the second data converted in accordance with the set mode;

a second calculation step of calculating fourth data in a device independent color space by performing an inverse conversion of the color appearance model based on the set mode and an output viewing condition,

wherein the color perception space is a relative color perception space when the relative mode is set, and an absolute color perception space when the absolute mode is set.