Image processing apparatus, image processing method, and program

• US 8,781,242 B2
• Filed: 09/15/2010
• Issued: 07/15/2014
• Est. Priority Date: 09/18/2009
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kobayashi, Masato
• Primary Examiner(s): Desire, Gregory M
• Application Number:
  US12/883,062
• Publication Number:
  US 20110069203A1
• Time in Patent Office: 1,399 Days
• Field of Search: 348/234, 348/674, 348/248, 382/162, 382/254, 382/268, 382/270, 382/272, 382/167, 382/274
• US Class Current: 382/254
• CPC Class Codes: H04N 5/205 for correcting amplitude versus frequency characteristic

Abstract

A method for processing an image includes acquiring a low frequency component of a luminance component of an image, correcting the luminance component of the image using the acquired low frequency component, determining a level correction amount of each pixel of the corrected image using a frequency distribution of low frequency components of the acquired image and a low frequency component of each pixel of the image, and performing level correction using the determined level correction amount and a luminance distribution of the corrected image.

Claims

1. An apparatus comprising at least one processor which functions as:

an acquisition unit configured to acquire a low frequency component of a luminance component of an image;

a correction unit configured to correct a luminance component of the image using the acquired low frequency component;

a determination unit configured to determine a level correction amount of pixels of the corrected image using a value obtained from a frequency distribution of the image corrected by the correction unit and a luminance component of pixels of the image corrected by the correction unit; and

a level correction unit configured to perform level correction on the corrected image using the determined level correction amount.

2. The apparatus according to claim 1, wherein the value is a median value of the frequency distribution of the image corrected by the correction unit,

wherein the determination unit calculates a difference between the median value and the luminance component of the pixels of the image corrected by the correction unit, and

wherein the larger the difference is, the smaller the level correction amount of pixels is.

3. The apparatus according to claim 1, wherein the correction unit corrects the luminance component of the image based on a result obtained by dividing a value of a luminance component of a pixel of the image by a value of a low frequency component corresponding to the pixel.

4. The apparatus according to claim 3, wherein the correction unit corrects the luminance component before the division by performing normalization of a value of luminance of the image subjected to the division so that an average value of the luminance component of the image subjected to the division becomes equal to an average value of the luminance component of the image before the division.

5. The apparatus according to claim 1, wherein the acquisition unit acquires the low frequency component of the luminance component by extracting the luminance component of the image and filtering the extracted luminance component.

6. The apparatus according to claim 1, wherein the value is an average value of the frequency distribution of the image corrected by the correction unit,

wherein the determination unit calculates a difference between the average value and the luminance component of the pixels of the image corrected by the correction unit, and

wherein the larger the difference is, the smaller the level correction amount of pixels is.

7. A method executed by an image processing apparatus, comprising:

acquiring a low frequency component of a luminance component of an image;

correcting a luminance component of the image using the acquired low frequency component;

determining a level correction amount of pixels of the corrected image using a value obtained from a frequency distribution of the corrected image and a luminance component of pixels of the corrected image; and

performing level correction on the corrected image using the determined level correction amount.

8. A non-transitory computer-readable medium storing a computer program for causing a computer to execute a method, the method comprising:

acquiring a low frequency component of a luminance component of an image;

correcting a luminance component of the image using the acquired low frequency component;

determining a level correction amount of pixels of the corrected image using a value obtained from a frequency distribution of the corrected image and a luminance component of pixels of the corrected image; and

performing level correction on the corrected image using the determined level correction amount.