Color conversion in image processing apparatus, image processing method and information processing apparatus, control method thereof, and non-transitory computer-readable medium

Patent metadata

Field	Value
Publication number	US-9959491-B2
Application number	US-201514962658-A
Country	US
Kind code	B2
Filing date	Dec 8, 2015
Priority date	Jan 20, 2015
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

An image processing apparatus decides a grid point coordinate on a lookup table corresponding to a predetermined color; calculates, based on association between a signal of the predetermined color in the uniform color space designated by a first color space information and the decided grid point coordinate, a first matrix for converting each signal in the uniform color space into a grid point coordinate; calculates, based on association between the signal of the predetermined color in the uniform color space designated by a second color space information and the decided grid point coordinate, a second matrix for converting each grid point coordinate into a signal in the uniform color space; and generates a lookup table for converting each grid point coordinate into a signal in the second color space by using the second matrix and the second color space information.

First claim

What is claimed is:

1. An image processing apparatus comprising:
a processor and a memory storing computer code that, when executed by the processor, causes the image processing apparatus to:
obtain a first signal that is a signal in a uniform color space by converting a signal corresponding to a predetermined color of an input image signal;
obtain a second signal that is a signal in a uniform color space by converting a signal corresponding to the predetermined color of a signal in a color space used by the image processing apparatus;
decide a grid point coordinate value on a lookup table that corresponds to the predetermined color;
associate a signal of the predetermined color in the uniform color space that is obtained as the first signal, with the decided grid point coordinate value, and based on the association calculate a first matrix for converting each signal in the uniform color space into a grid point coordinate value;
associate the signal of the predetermined color in the uniform color space that is obtained as the second signal, with the decided grid point coordinate value, and based on the association calculate a second matrix for converting each grid point coordinate value into a signal in the uniform color space;
generate a lookup table for converting each grid point coordinate value into a signal in the color space used by the image processing apparatus by using the second matrix and color space information for converting a signal in the uniform color space into a signal in the color space used by the image processing apparatus; and
convert the input image signal into the signal in the color space used by the image processing apparatus by using the first matrix and the lookup table, to print the converted input image signal.

2. The apparatus according to claim 1 , wherein the predetermined color includes white or a plurality of types of colors including white.

3. The apparatus according to claim 2 , wherein the computer code, when executed by the processor, causes the image processing apparatus to receive designation of a type of the predetermined color.

4. The apparatus according to claim 3 , wherein a value of a signal of the predetermined color in the uniform color space is further received.

5. The apparatus according to claim 4 , wherein the computer code, when executed by the processor, causes the image processing apparatus to, if a value of a signal of white in the uniform color space that has been received is different from a value of a signal of white in the uniform color space that is obtained as the first signal value, correct, based on a difference between the values, a value of a signal of a predetermined color other than white in the uniform color space that has been designated,
wherein calculation of matrices is performed using the value of the signal corrected.

6. The apparatus according to claim 2 , wherein the grid point coordinate value decided is defined in advance for each type of the predetermined color.

7. The apparatus according to claim 1 , wherein a signal of white represented as the first signal and a signal of white represented as the second signal are identical.

8. The apparatus according to claim 1 , wherein a signal of white represented as the first signal and a signal of white represented as the second signal are different.

9. The apparatus according to claim 1 , wherein pieces of color space are defined as candidates of the color space used by the image processing apparatus, and
the computer code, when executed by the processor, causes the image processing apparatus to receive a selection of the color space used by the image processing apparatus from the pieces of color space.

10. An image processing method for an image processing apparatus comprising:
obtaining a first signal that is a signal in a uniform color space by converting a signal corresponding to a predetermined color of an input image signal;
obtaining a second signal that is a signal in a uniform color space by converting a signal corresponding to the predetermined color of a signal in a color space used by the image processing apparatus;
deciding a grid point coordinate value on a lookup table that corresponds to the predetermined color;
associating a signal of the predetermined color in the uniform color space that is obtained as the first signal, with the decided grid point coordinate value, and based on the association calculating a first matrix for converting each signal in the uniform color space into a grid point coordinate value;
associating the signal of the predetermined color in the uniform color space that is obtained as the second signal, with the grid point coordinate value decided, and based on the association calculating a second matrix for converting each grid point coordinate value into a signal in the uniform color space;
generating a lookup table for converting each grid point coordinate value into a signal in the color space used by the image processing apparatus by using the second matrix and color space information for converting a signal in the uniform color space into a signal in the color space used by the image processing apparatus; and
converting the input image signal into the signal in the color space used by the image processing apparatus by using the first matrix and the lookup table, to print the converted input image signal.

11. A non-transitory computer-readable medium storing a program for causing a computer to:
obtain a first signal that is a signal in a uniform color space by converting a signal corresponding to a predetermined color of an input image signal;
obtain a second signal that is a signal in a uniform color space by converting a signal corresponding to the predetermined color of a signal in a color space used by the computer;
decide a grid point coordinate value on a lookup table that corresponds to the predetermined color;
associate a signal of the predetermined color in the uniform color space that is obtained as the first signal, with the decided grid point coordinate value, and based on the association calculate a first matrix for converting each signal in the uniform color space into a grid point coordinate value;
associate the signal of the predetermined color in the uniform color space that is obtained as the second signal, with the grid point coordinate value decided, and based on the association calculate a second matrix for converting each grid point coordinate value into a signal in the uniform color space;
generate a lookup table for converting each grid point coordinate value into a signal in the color space used by the computer by using the second matrix and color space information for converting a signal in the uniform color space into a signal in the color space used by the computer; and
convert the input image signal into the signal in the color space used by the computer by using the first matrix and the lookup table, to print the converted input image signal.

Assignees

• Canon Kk

Inventors

• Oka Hiroyuki

Classifications

• G06K15/1878 Primary

  Adjusting colours (image colour correction or control for documents in general H04N1/60) · CPC title

• G06K15/1825

  Adapting the print data to an output condition, e.g. object trapping (trapping on rasterized data H04N1/58) · CPC title

• H04N1/603

  controlled by characteristics of the picture signal generator or the picture reproducer · CPC title