Image processing apparatus and control method therefor

Patent metadata

Field	Value
Publication number	US-9338419-B2
Application number	US-201514629976-A
Country	US
Kind code	B2
Filing date	Feb 24, 2015
Priority date	Jun 22, 2012
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

An image processing apparatus is provided that allows accurate white balance gains to be obtained by accurately estimating the illuminant colors of various objects in an image. The white balance gains are obtained based on values of white pixels that have been extracted from an input image and have colors included in an extraction range, and the white balance gains are obtained based on specular reflection components included in the input image, are mixed in accordance with a mix ratio. The mix ratio is determined in accordance with, for example, a degree of reliability of extraction of the white pixels.

First claim

What is claimed is:

1. An image processing apparatus comprising:
a pixel extraction unit that extracts, from an input image, pixels having an achromatic color that are included in a predetermined extraction range in a predetermined color space;
a component extraction unit that extracts specular reflection components included in the input image; and
an obtainment unit that obtains white balance gains used for the input image based on both a result of a pixel extraction by the pixel extraction unit and a result of a component extraction by the component extraction unit.

2. The image processing apparatus according to claim 1 , wherein the obtainment unit obtains the white balance gains based on a degree of reliability of the pixel extraction or on a degree of reliability of the component extraction.

3. The image processing apparatus according to claim 1 , wherein the obtainment unit uses first white balance gains based on values of the extracted pixels as the white balance gains when a degree of reliability of the pixel extraction is higher than a degree of reliability of the component extraction, and uses second white balance gains based on the extracted specular reflection components as the white balance gains when the degree of reliability of the component extraction is higher than the degree of reliability of the pixel extraction.

4. The image processing apparatus according to claim 1 , further comprising a first degree of reliability obtainment unit that obtains a degree of reliability of the pixel extraction performed by the pixel extraction unit, wherein the first degree of reliability obtainment unit obtains the degree of reliability of the pixel extraction based on at least one of:
a first degree of reliability of extraction that is higher for a larger ratio of the number of the pixels extracted by the pixel extraction unit to the number of pixels included in the input image;
a second degree of reliability of extraction that is lower for a larger range of distribution of the values of the pixels extracted by the pixel extraction unit; and
a third degree of reliability of extraction that is lower for a larger ratio of the number of pixels that are included in the input image and have colors included in a predetermined range to the number of the pixels extracted by the pixel extraction unit.

5. The image processing apparatus according to claim 1 , further comprising a second degree of reliability obtainment unit that obtains a degree of reliability of the component extraction performed by the component extraction unit, wherein the second degree of reliability obtainment unit obtains the degree of reliability of the component extraction based on at least one of:
a first degree of reliability of specular reflection that is higher for a larger ratio of regions that have been determined to include specular reflection components to the input image;
a second degree of reliability of specular reflection that is lower for a larger ratio of regions that have been determined to include edges to the input image; and
a third degree of reliability of specular reflection that is lower for a larger range of distribution of values of the specular reflection components extracted by the component extraction unit.

6. The image processing apparatus according to claim 1 , further comprising:
a first obtainment unit that obtains first white balance gains corresponding to the input image based on values of the extracted pixels; and
a second obtainment unit that obtains second white balance gains corresponding to the input image based on the extracted specular reflection components,
wherein the obtainment unit obtains the white balance gains used for the input image based on the first white balance gains and on the second white balance gains.

7. The image processing apparatus according to claim 6 , wherein the obtainment unit obtains the white balance gains used for the input image by combining the first white balance gains and the second white balance gains based on a degree of reliability of the first white balance gains or on a degree of reliability of the second white balance gains.

8. A method for controlling an image processing apparatus, comprising:
extracting, from an input image, pixels having an achromatic color that are included in a predetermined extraction range in a predetermined color space;
extracting specular reflection components included in the input image; and
obtaining white balance gains used for the input image based on both a result of a pixel extraction and a result of a specular reflection component extraction.

9. A non-transitory computer-readable medium having stored therein a program for causing a computer to function as an image processing apparatus comprising:
a pixel extraction unit that extracts, from an input image, pixels having an achromatic color that are included in a predetermined extraction range in a predetermined color space;
a component extraction unit that extracts specular reflection components included in the input image; and
an obtainment unit that obtains white balance gains used for the input image based on both a result of a pixel extraction by the pixel extraction unit and a result of a component extraction by the component extraction unit.

10. The method according to claim 8 , wherein the obtaining comprises:
obtaining first white balance gains corresponding to the input image based on values of the extracted pixels;
obtaining second white balance gains corresponding to the input image based on the extracted specular reflection components; and
obtaining the white balance gains used for the input image based on the first white balance gains and the second white balance gains.

Assignees

• Canon Kk

Inventors

• Kitajima Kotaro

Classifications

• H04N23/88 Primary

  for colour balance, e.g. white-balance circuits or colour temperature control · CPC title

• G06K9/46

  Physics · mapped topic

• H04N9/735 Primary

  Electricity · mapped topic