Image processing method and apparatus for suppressing positional shift image degradation

• US 7,689,065 B2
• Filed: 11/18/2004
• Issued: 03/30/2010
• Est. Priority Date: 11/21/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Fukuda, Yasuo
• Primary Examiner(s): Ahmed; Samir A.
• Assistant Examiner(s): Liu; Li
• Application Number:
  US10/990,375
• Publication Number:
  US 20050110882A1
• Time in Patent Office: 1,958 Days
• Field of Search: 382/318, 382/319, 382/162, 382/264, 382/282, 382/299
• US Class Current: 382/318
• 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:

using an image processing apparatus to perform the following steps;

a first acquisition step of acquiring, by using an image input unit, first image data of an inputted image at a first resolution;

a storage step of extracting first low-frequency components of luminance values from the first image data, and storing the extracted first low-frequency components in a memory;

a second acquisition step of acquiring second image data of each of divided areas into which the inputted image is divided, said second image data being acquired at a second resolution higher than the first resolution;

a low-frequency extraction step of extracting a second low-frequency components of luminance values from the second image data;

an image processing step of performing image processing for the second image data, using both the extracted second low-frequency components and low-frequency components of an area corresponding to the divided area in the inputted image among the first low-frequency components stored in the memory,

wherein the second acquisition step, the low-frequency extraction step, and the image processing step are performed in sequence for each of the divided areas.

2. The method according to claim 1, wherein the first low-frequency components are obtained by applying a two dimensional filter to the luminance values in the first image data.

3. The method according to claim 1, wherein the second image data is for band images into which the inputted image is segmented in a subscanning direction.

4. The method according to claim 3, further comprising a holding step of holding luminance values of a predetermined number of last lines of an immediately processed band image,

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

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

6. The method according to claim 1, further comprising:

a preview input st ep 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, as the inputted image, from the plurality of preview images, in accordance with an instruction from a user.

7. An image processing apparatus comprising:

a first acquisition unit configured to acquire first image data of an inputted image at a first resolution;

a storage unit to extract first low-frequency components of luminance values from the first image data, and to store the extracted first low-frequency components in a memory;

a second acquisition unit configured to acquire second image data of each of divided areas into which the inputted image is divided, said second image data being acquired at a second resolution higher than the first resolution;

a low-frequency extraction unit to extract second low-frequency components of luminance values from the second image data;

an image processing unit to perform image processing for the second image data, using both the extracted second low-frequency components and low-frequency components of an area corresponding to the divided area in the inputted image among the first low-frequency components stored in the memory,

wherein the functions performed by the second acquisition unit, the low-frequency extraction unit, and the image processing unit are performed in sequence for each of the divided areas.

8. A program stored on a computer-readable medium for causing a computer to execute a processing method comprising:

a first acquisition procedure of acquiring first image data image of an inputted image at a first resolution;

a storage procedure of extracting first low-frequency components of luminance values from the first image data, and storing the extracted first low-frequency components in a memory;

a second acquisition procedure of acquiring second image data of each of divided areas into which the inputted image is divided, said second image data being acquired at a second resolution higher than the first resolution;

a low-frequency extraction procedure of extracting second low-frequency components of luminance values from the second image data;

an image processing procedure configured to perform image processing for the second image data, using both the extracted second low-frequency components and low-frequency components of an area corresponding to the divided area in the inputted image among the stored first low-frequency components stored in the memory,

wherein the second acquisition procedure, the low-frequency extraction procedures and the image processing procedure are performed in sequence for each of the divided areas.