Image processing apparatus and method, and image capturing apparatus

Patent metadata

Field	Value
Publication number	US-10825136-B2
Application number	US-201816122040-A
Country	US
Kind code	B2
Filing date	Sep 5, 2018
Priority date	Sep 13, 2017
Publication date	Nov 3, 2020
Grant date	Nov 3, 2020

Abstract

An image processing apparatus comprises: first and generation units that generate color signal components for luminance and color signal components for color difference, respectively, in a first color space from an input image signal; an integration unit that integrates the color signal components for luminance and color difference to generate color signal components common for luminance and color difference; a processing unit that performs nonlinear processing on the color signal components common for luminance and color difference; a separation unit that generates luminance and color difference signals in a second color space from the signal that has undergone the nonlinear processing; and a band limiting unit that performs band limitation processing on the color difference signals. A characteristic of the band limitation processing is set on the basis of frequency characteristics of the luminance color difference signals.

First claim

What is claimed is:

1. An image processing apparatus comprising one or more processors and/or circuitry which functions as:
a first generation unit that generates color signal components for luminance in a first color space from an input image signal;
a second generation unit that generates color signal components for color difference in the first color space from the image signal;
an integration unit that integrates the color signal components for luminance and the color signal components for color difference to generate color signal components common for luminance and color difference;
a processing unit that performs nonlinear processing on the color signal components common for luminance and color difference;
a separation unit that generates a luminance signal and color difference signals in a second color space from the signal that has undergone the nonlinear processing; and
a band limiting unit that performs band limitation processing on the color difference signals,
wherein a characteristic of the band limitation processing is set on the basis of frequency characteristics of the luminance signal and the color difference signals.

2. The image processing apparatus according to claim 1 , wherein the second generation unit performs demosaicing processing and then thinning processing at a predetermined pixel cycle on the color signal components for color difference, and
at least the one processor or the one circuitry also functions as a phase compensation unit that performs phase compensation processing before the integration is performed by the integration unit on the color signal components for color differences that have undergone the thinning processing by the second generation unit.

3. The image processing apparatus according to claim 2 , wherein the second generation unit performs the thinning processing every other pixel.

4. The image processing apparatus according to claim 2 , wherein the phase compensation processing is to generate a thinned-out color difference signal from at least two color difference signals which are not thinned.

5. The image processing apparatus according to claim 1 , wherein the band limiting unit performs the band limitation processing using a filter.

6. The image processing apparatus according to claim 5 , wherein the filter has a characteristic that a gain is 0 at a maximum frequency of the color difference signals.

7. The image processing apparatus according to claim 5 , wherein the characteristic of the filter is set on the basis of the characteristics of the nonlinear processing performed by the processing unit.

8. The image processing apparatus according to claim 5 , wherein the characteristic of the filter is set on the basis of an imaging sensitivity of the image signal.

9. The image processing apparatus according to claim 1 , wherein the nonlinear processing performed by the processing unit is based on an inverse characteristic to an electrooptical (EOTF) characteristic defined for a high dynamic range (HDR) compatible monitor.

10. The image processing apparatus according to claim 1 , wherein at least the one processor or the one circuitry also functions as a thinning unit that performs thinning processing at a predetermined pixel cycle on the color difference signals which have undergone the band limitation processing by the band limiting unit.

11. The image processing apparatus according to claim 1 , wherein the first color space is a color space of a color mixing system.

12. The image processing apparatus according to claim 11 , wherein the first color space is an RGB color space, an XYZ color space or an LMS color space.

13. The image processing apparatus according to claim 1 , wherein the second color space is a color space of a color-luminance separation system.

14. The image processing apparatus according to claim 13 , wherein the second color space is a YUV color space or an ICtCp color space.

15. An image capturing apparatus comprising:
an image sensor that performs photoelectric conversion on an incident optical image and outputs an image signal; and
an image processing apparatus comprising one or more processors and/or circuitry which functions as:
a first generation unit that generates color signal components for luminance in a first color space from an input image signal;
a second generation unit that generates color signal components for color difference in the first color space from the input image signal;
an integration unit that integrates the color signal components for luminance and the color signal components for color difference to generate color signal components common for luminance and color difference;
a processing unit that performs nonlinear processing on the color signal components common for luminance and color difference;
a separation unit that generates a luminance signal and color difference signals in a second color space from the signal that has undergone the nonlinear processing; and
a band limiting unit that performs band limitation processing on the color difference signals,

wherein a characteristic of the band limitation processing is set on the basis of frequency characteristics of the luminance signal and the color difference signals.

16. An image processing method comprising:
generating color signal components for luminance in a first color space from an input image signal;
generating color signal components for color difference in the first color space from the image signal;
integrating the color signal components for luminance and the color signal components for color difference to generate color signal components common for luminance and color difference;
performing nonlinear processing on the color signal components common for luminance and color difference;
generating a luminance signal and color difference signals in a second color space from the signal that has undergone the nonlinear processing; and
performing band limitation processing on the color difference signals,
wherein a characteristic of the band limitation processing is set on the basis of frequency characteristics of the luminance signal and the color difference signals.

17. A non-transitory storage medium readable by a computer, the storage medium storing a program that is executable by the computer, wherein the program includes program code for causing the computer to function as an image processing apparatus comprising:
a first generation unit that generates color signal components for luminance in a first color space from an input image signal;
a second generation unit that generates color signal components for color difference in the first color space from the image signal;
an integration unit that integrates the color signal components for luminance and the color signal components for color difference to generate color signal components common for luminance and color difference;
a processing unit that performs nonlinear processing on the color signal components common for luminance and color difference;
a separation unit that generates a luminance signal and color difference signals in a second color space from the signal that has undergone the nonlinear processing; and
a band limiting unit that performs band limitation processing on the color difference signals,
wherein a characteristic of the band limitation processing is set on the basis of frequency characteristics of the luminance signal and the color difference signals.

Assignees

• Canon Kk

Inventors

• Yamaguchi Shota

Classifications

• H04N23/12

  with one sensor only · CPC title

• H04N23/85

  for matrixing · CPC title

• H04N9/646

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

• H04N1/409

  Edge or detail enhancement; Noise or error suppression · CPC title

• G06T3/4015 Primary

  Image demosaicing, e.g. colour filter arrays [CFA] or Bayer patterns · CPC title