Image processing method and apparatus

• US 20050110882A1
• Filed: 11/18/2004
• Published: 05/26/2005
• Est. Priority Date: 11/21/2003
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Fukuda, Yasuo
• Granted Patent: US 7,689,065 B2
• Time in Patent Office: Days
• US Class Current: 348/234
• CPC Class Codes: G06T 2207/20016 Hierarchical, coarse-to-fine, multiscale or multiresolution image processing; Pyramid transform
• CPC Class Codes: G06T 3/40 Scaling of whole images or parts thereof, e.g. expanding or contracting
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement
• CPC Class Codes: H04N 1/4072 dependent on the contents of the original

Abstract

There are provided an image processing method and apparatus which can reduce the storage capacity required to form low-frequency components having a plurality of resolutions and can suppress any degradation in image quality which is caused by a positional error between image data obtained as a result of image processing. The first luminance component of low resolution is extracted from image data, thereby further extracting the first low-frequency component. The image data is input at the second resolution, the second luminance component is extracted from the image data at the second resolution, and the second low-frequency component is extracted, thereby further extracting the second low-frequency component. Image processing is performed for the image data at the second resolution using the first low-frequency component and second low-frequency component.

Claims

1. An image processing method comprising:

a first acquisition step of acquiring first image data indicating an original image;

a first luminance extraction step of extracting a first luminance component from the first image data;

a first low-frequency extraction step of extracting a first low-frequency component from the first luminance component;

a second acquisition step of acquiring second image data indicating the original image;

a second luminance extraction step of extracting a second luminance component from the second image data;

a second low-frequency extraction step of extracting a second low-frequency component from the second luminance component; and

an image processing step of performing image processing for the second image data using the first low-frequency component and second low-frequency component,

wherein a resolution of the first low-frequency component is lower than a resolution of the second low-frequency component.

2. The method according to claim 1, wherein a resolution of the first image data is lower than a resolution of the second image data.

3. The method according to claim 1, wherein the second acquisition step, second luminance extraction step, second low-frequency extraction step, and image processing step are performed for each of a plurality of regions into which the second image data indicating the original image is segmented in a subscanning direction.

4. The method according to claim 3, further comprising a holding step of holding the second luminance component by a predetermined number of last lines of an immediately processed segmented region,

wherein the predetermined number of lines are determined on the basis of a size of a processing region of a low-frequency signal extraction process to be performed for pixels in the second low-frequency extraction process.

5. The method according to claim 1, further comprising a preview step of performing preview on the basis of the first image data.

6. The method according to claim 1, wherein in the first acquisition step and second acquisition step, the original image is scanned, and the first image data and the second image data whose resolution is lower than a resolution of the first image data, respectively, are acquired.

7. The method according to claim 6, further comprising:

a preview input step of optically scanning a plurality of documents arranged on a scanning surface and inputting a plurality of preview images; and

a selection step of selecting a preview image in accordance with an instruction from a user, from the plurality of preview images,

wherein the original image scanned in the first acquisition step and second acquisition step is a document corresponding to the preview image selected in the selection step.

8. An image processing apparatus comprising:

first acquisition unit configure to acquire first image data indicating an original image;

first luminance extraction unit configure to extract a first luminance component from the first image data;

first low-frequency extraction unit configure to extract a first low-frequency component from the first luminance component;

second acquisition unit configure to acquire second image data indicating the original image;

second luminance extraction unit configure to extract a second luminance component from the second image data;

second low-frequency extraction unit configure to extract a second low-frequency component from the second luminance component; and

image processing unit configure to perform image processing for the second image data using the first low-frequency component and second low-frequency component,

wherein a resolution of the first low-frequency component is lower than a resolution of the second low-frequency component.

9. A program causing a computer to execute:

a first acquisition procedure for acquiring first image data indicating an original image;

a first luminance extraction procedure for extracting a first luminance component from the first image data;

a first low-frequency extraction procedure for extracting a first low-frequency component from the first luminance component;

a second acquisition procedure for acquiring second image data indicating the original image;

a second luminance extraction procedure for extracting a second luminance component from the second image data;

a second low-frequency extraction procedure for extracting a second low-frequency component from the second luminance component; and

an image processing procedure for performing image processing for the second image data using the first low-frequency component and second low-frequency component,

wherein a resolution of the first low-frequency component is lower than a resolution of the second low-frequency component.

10. A computer-readable recording medium storing a program defined in claim 9.