Image processing apparatus, image processing method, and storage medium for performing correction for a target pixel having high luminance in an image

Patent metadata

Field	Value
Publication number	US-10440339-B2
Application number	US-201715693069-A
Country	US
Kind code	B2
Filing date	Aug 31, 2017
Priority date	Sep 9, 2016
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

A reflection correction processing unit extracts at least color information from a peripheral area of a processing target pixel having a high luminance in an input image, and performs control, to the processing target pixel, to reduce the luminance of the processing target pixel and to bring a chrominance signal of the processing target pixel close to a predetermined chrominance signal ratio. In a case where a chrominance signal ratio based on the color information is close to the predetermined chrominance signal ratio, the reflection correction processing unit increases an intensity of the correction to the processing target pixel.

First claim

What is claimed is:

1. An image processing apparatus comprising:
at least one processor and/or circuit configured to function as following units:
a detection unit configured to detect a specific object area from an image;
a correction processing unit configured to perform correction, on a processing target pixel having a luminance higher than a predetermined value in the image, to reduce the luminance of the processing target pixel and to bring a chrominance signal ratio of the processing target pixel closer to a predetermined chrominance signal ratio, wherein the predetermined chrominance signal ratio corresponds to a representative color of the specific object area; and
an extraction unit configured to extract at least color information from a peripheral area of the processing target pixel in the image,
wherein the correction processing unit compares a chrominance signal ratio based on the color information with the predetermined chrominance signal ratio and controls an intensity of the correction to the processing target pixel according to a comparison result.

2. The image processing apparatus according to claim 1 , wherein the extraction unit changes the peripheral area based on the luminance of the processing target pixel.

3. The image processing apparatus according to claim 2 , wherein the extraction unit sets a range of the peripheral area wider when the luminance of the processing target pixel is higher.

4. The image processing apparatus according to claim 1 , wherein the extraction unit extracts the color information from a plurality of the peripheral areas, the number of the plurality of the peripheral areas being more than two, the plurality of the peripheral areas being different from each other in size.

5. The image processing apparatus according to claim 4 ,
wherein the extraction unit generates information about a color correction weight by adding a weight to the color information extracted from the plurality of the peripheral areas, based on the luminance of the processing target pixel, and
wherein the correction processing unit performs the correction on the processing target pixel based on the information about the color correction weight.

6. The image processing apparatus according to claim 5 , wherein the extraction unit generates the information about the color correction weight by obtaining information about a color weight for each of the plurality of the peripheral areas based on a color distance representing a difference in color between the color information extracted from the plurality of the peripheral areas and a reference color and adding the information about the color weights of the plurality of the peripheral areas based on the luminance of the processing target pixel.

7. The image processing apparatus according to claim 5 , wherein the correction processing unit performs the correction by generating a correction signal to the processing target pixel through multiplication of the color correction weight by a luminance correction weight obtained based on the luminance of the processing target pixel and subtracting the correction signal from a chrominance signal of the processing target pixel.

8. The image processing apparatus according to claim 7 , wherein the correction processing unit calculates the luminance correction weight by subtracting a luminance signal, which is obtained by subjecting a luminance signal of the input image to low-pass filter processing, from the luminance signal in the input image.

9. The image processing apparatus according to claim 1 , wherein the extraction unit sets, as the peripheral area, an area including pixels which differ from the processing target pixel in one or more of pixel features including a luminance, a color, and a normal line.

10. The image processing apparatus according to claim 9 , wherein the extraction unit sets, in a case where an area including pixels, which differ from the processing target pixel in luminance, is set as a peripheral area, an area including pixels each having a luminance lower than the luminance of the processing target pixel as the peripheral area.

11. The image processing apparatus according to claim 9 , wherein the extraction unit sets, in a case where an area including pixels, which differ from the processing target pixel in color, is set as a peripheral area, an area including pixels each having a color saturation higher than color saturation of the processing target pixel as the peripheral area.

12. The image processing apparatus according to claim 9 , wherein the extraction unit sets, in a case where an area including pixels, which differ from the processing target pixel in a normal line, is set as a peripheral area, an area including pixels, which differ from the processing target pixel in a normal line direction by a predetermined angle or more, as the peripheral area.

13. The image processing apparatus according to claim 1 , wherein the extraction unit changes a range of the peripheral area based on the size of the specific object area.

14. The image processing apparatus according to claim 1 , further comprising:
a ranging unit configured to detect an object distance,
wherein the extraction unit extracts the color information from an area having a predetermined threshold distance or less with respect to an object distance of the processing target pixel, in the peripheral area.

15. The image processing apparatus according to claim 1 , wherein
the specific object area is a face area of an object, and
the representative color is a skin color.

16. An image processing method comprising:
detecting a specific object area from an image;
performing correction, on a processing target pixel having a luminance higher than a predetermined value in the image, to reduce the luminance of the processing target pixel and to bring a chrominance signal ratio of the processing target pixel closer to a predetermined chrominance signal ratio, wherein the predetermined chrominance signal ratio corresponds to a representative color of the specific object area; and
extracting at least color information from a peripheral area of the processing target pixel in the image,
wherein the performing correction compares a chrominance signal ratio based on the color information with the predetermined chrominance signal ratio, and controls an intensity of the correction to the processing target pixel according to a comparison result.

17. The image processing method according to claim 16 , further comprising:
detecting an object distance,
wherein the extracting extracts the color information from an area having a predetermined threshold distance or less with respect to an object distance of the processing target pixel, in the peripheral area.

18. A computer readable non-transitory storage medium storing a control program for causing a computer to execute an image processing method used in an image processing apparatus, the image processing method comprising:
detecting a specific object area from an image;
performing correction, on a processing target pixel having a luminance higher than a predetermined value in the image, to reduce the luminance of the processing target pixel and to bring a chrominance signal ratio of the processing target pixel closer to a predetermined chrominance signal ratio, wherein the predetermined chrominance signal ratio corresponds to a representative color of the specific object area; and
extracting at least color information from a peripheral area of the processing target pixel in the image,
wherein the performing correction compares a chrom

Assignees

• Canon Kk

Inventors

• Kitajima Kotaro

Classifications

• H04N9/646 Primary

  for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters · CPC title

• H04N23/84

  for processing colour signals · CPC title

• H04N23/70

  Circuitry for compensating brightness variation in the scene · CPC title

• G06V40/16

  Human faces, e.g. facial parts, sketches or expressions · CPC title

• G06T7/90

  Determination of colour characteristics · CPC title