Image processing apparatus, image processing method, and computer-readable medium

• US 8,934,712 B2
• Filed: 05/16/2013
• Issued: 01/13/2015
• Est. Priority Date: 07/16/2010
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Sakai, Hiroyuki, Nakagawa, Junichi, Umeda, Kiyoshi
• Primary Examiner(s): COUSO, JOSE L
• Application Number:
  US13/896,258
• Publication Number:
  US 20130251259A1
• Time in Patent Office: 607 Days
• Field of Search: 382162-168, 382/190, 382/254, 382274-275, 358/1.9, 358/3.27, 358/516, 358518-520, 358/523, 348/221.1, 348/223.12
• US Class Current: 382/167
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: H04N 1/6077 Colour balance, e.g. colour cast correction
• 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 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 9/643 Hue control means, e.g. flesh tone control
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

An image processing apparatus for applying a color balance correction to input image data, comprises a holding unit which holds information indicating a locus of a change in highlight color when a color temperature for image data is changed on a color space; a highlight color calculation unit which calculates a highlight color from the image data; a distance calculation unit which calculates a distance between the highlight color and the highlight color locus held in the holding unit on the color space; a reliability calculation unit which calculates a reliability for a value of the highlight color calculated by the highlight color calculation unit in accordance with the distance calculated by the distance calculation unit; and a color balance correction unit which applies the color balance correction to the image data using the highlight color and the reliability.

Claims

1. An image processing apparatus comprising:

at least one processor;

an acquisition unit configured to acquire a highlight color in an image;

a determination unit configured to determine a degree of correction for the highlight color acquired by the acquisition unit based on the highlight color acquired by the acquisition unit and a highlight color held preliminary;

a correction unit configured to correct the highlight color acquired by the acquisition unit in accordance with the degree of correction determined by the determination unit; and

a color balance correction unit configured to correct a color balance in the image in accordance with the highlight color corrected by the correction unit.

2. The apparatus according to claim 1, wherein the correction unit corrects the highlight color acquired by the acquisition unit so as to be closer to an origin on a color space.

3. The apparatus according to claim 2, wherein the color space is a space for color difference components.

4. The apparatus according to claim 1, wherein the highlight color acquired by the acquisition unit is acquired using a histogram of a luminance component of the image.

5. The apparatus according to claim 1, wherein the highlight color held preliminary is a color on a locus of a highlight color.

6. The apparatus according to claim 1, wherein the highlight color held preliminary is a color on a blackbody locus of a highlight color.

7. The apparatus according to claim 1, wherein a determination by the determination unit is performed using a distance between the highlight color acquired by the acquisition unit and the highlight color held preliminary on the color space.

8. The apparatus according to claim 7, wherein the degree of correction for the highlight color acquired by the acquisition unit is larger with increasing the distance.

10. A non-transitory computer-readable medium storing a program for controlling a computer to function as an image processing apparatus according to claim 1.

9. An image processing method comprising:

using at least one processor to perform the steps of;

acquiring a highlight color in an image;

determining a degree of correction for the highlight color acquired in the acquiring step based on the highlight color acquired in the acquiring step and a highlight color held preliminary;

correcting the highlight color acquired in the acquiring step in accordance with the degree of correction determined in the determining step; and

correcting a color balance in the image in accordance with the highlight color corrected in the correcting step.