Image Processing Method

• US 20080199100A1
• Filed: 03/31/2006
• Published: 08/21/2008
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Ishiga, Kenichi
• Granted Patent: US 8,059,910 B2
• Time in Patent Office: Days
• US Class Current: 382/263
• CPC Class Codes: G06T 2207/20016 Hierarchical, coarse-to-fine, multiscale or multiresolution image processing; Pyramid transform
• CPC Class Codes: G06T 2207/20064 Wavelet transform [DWT]
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/10 using non-spatial domain filtering
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing

Abstract

An image processing method for removing noise contained in an image includes: inputting an original image constituted with a plurality of pixels; generating a plurality of band-limited images, resolution levels of which are lowered in sequence, by executing a specific type of band pass filter processing on the original image; extracting a high-frequency component from each of the band-limited images by executing high-pass filter processing on the band-limited images; extracting a noise component contained in each of the band-limited images by separating the noise component through nonlinear conversion processing executed on the extracted high-frequency component; and removing the noise in the original image based upon the extracted noise component in each band-limited image.

Claims

1. An image processing method for removing noise contained in an image, comprising:

inputting an original image constituted with a plurality of pixels;

extracting a first high-frequency component through first high-pass filter processing executed on the original image;

extracting a second high-frequency component through second high-pass filter processing executed on the extracted first high-frequency component;

extracting a noise component by separating the noise component through nonlinear conversion processing executed on the extracted second high-frequency component; and

removing the noise in the original image based upon the extracted noise component.

2. An image processing method according to claim 1, wherein:

a plurality of high-frequency band-limited images corresponding to the first high-frequency component, resolution levels of which are lowered in sequence, are generated through a specific type of band pass filter processing including the first high-pass filter processing, executed on the original image;

the second high-frequency component is extracted from each of the high-frequency band-limited images by individually executing the second high-pass filter processing on the plurality of high-frequency band-limited images having been generated;

the noise component contained in each of the high-frequency band-limited images is extracted by separating the noise component through the nonlinear conversion processing executed on the extracted second high-frequency component; and

the noise in the original image is removed based upon the noise component extracted from each of the high-frequency band-limited images.

7. An image processing method according to claim 1, wherein:

the nonlinear conversion processing is attenuation processing whereby a non-noise component contained in the second high-frequency component is attenuated by multiplying the second high-frequency component by a weighted Gaussian coefficient having an argument of a value resulting from a comparison of the second high-frequency component with a predetermined threshold value.

8. An image processing method according to claim 2, wherein:

the second high-pass filter processing is executed on the plurality of high-frequency band-limited images by using filters of uniform size.

15. An image processing method according to claim 7, wherein:

a standard deviation value determined in a uniform image area of the original image is used as the predetermined threshold value.

26. A computer-readable computer program product, comprising:

an image processing program that enables a computer or an image processing apparatus to execute an image processing method according to claim 1.

27. An image processing apparatus, comprising:

a control device that executes an image processing method according to claim 1.

3. An image processing method according to claim 3, wherein:

the plurality of high-frequency band-limited images are a set of high-frequency band images, the resolution levels of which are lowered in sequence, obtained through multi-resolution transformation executed on the original image.

5. An image processing method according to claim 3, wherein:

the plurality of high-frequency band-limited images are a set of high-pass component sub-band images resulting from wavelet transformation.

4. (canceled)

6. (canceled)

9. An image processing method for removing noise contained in an image, comprising:

obtaining the image;

extracting a noise component by executing a specific type of processing on the obtained image;

subtracting the extracted noise component from the image;

extracting a correction component by re-executing the specific type of processing on the image from which the noise component has been subtracted; and

adding the extracted correction component to the image from which the noise component has been subtracted.

10. An image processing method according to claim 9, wherein:

a high-frequency component is extracted from the obtained image;

the noise component is extracted from the extracted high-frequency component through nonlinear conversion;

a high-frequency component is extracted again from the image from which the noise component has been subtracted;

the correction component is extracted from the re-extracted high-frequency component through the nonlinear conversion; and

the extracted correction component is added to the image from which the noise component has been subtracted.

11. An image processing method according to claim 9, wherein:

the image is constituted with a luminance component and a chrominance component; and

processing for adding the correction component to the image from which the noise component has been subtracted is executed for an image corresponding to the luminance component alone.

23. An image processing method according to claim 9, wherein:

processing for extracting a noise component through the specific type of processing executed again on the image to which the correction component has been added, subtracting the extracted noise component from the image, extracting a correction component through the specific type of processing executed again on the image from which the noise component has been subtracted and adding the extracted correction component to the image from which the noise component has been subtracted is repeated at least once.

12. An image processing method for removing noise contained in an image, comprising:

inputting an original image expressed by using a luminance component and a chrominance component;

generating a plurality of band-limited images, resolution levels of which are lowered in sequence, by filtering the original image; and

executing noise removal processing on the plurality of band-limited images by referencing nearby pixels, wherein;

a procedure for referencing nearby pixels in the noise removal processing executed on the band-limited images corresponding to the luminance component and a procedure for referencing nearby pixels in the noise removal processing executed on the band-limited images corresponding to the chrominance component are different from each other.

13. An image processing method according to claim 12, wherein:

the noise removal processing on the band-limited images corresponding to the chrominance component is executed by extracting a high-frequency component from a band-limited image corresponding to the chrominance component, extracting a noise component through nonlinear conversion processing executed on the extracted high-frequency component and then subtracting the extracted noise component from the band-limited image corresponding to the chrominance component; and

the noise removal processing on the band-limited images corresponding to the luminance component is executed by extracting a high-frequency component from a band-limited image corresponding to the luminance component, extracting a noise component through nonlinear conversion processing executed on the extracted high-frequency component, executing subtraction processing to subtract the extracted noise component from the band-limited image corresponding to the luminance component, re-extracting a high-frequency component from the band-limited image corresponding to the luminance component having undergone the subtraction processing, extracting a correction component through nonlinear conversion processing executed on the re-extracted high-frequency component and adding the extracted correction component to the band-limited image corresponding to the luminance component having undergone the subtraction processing.

24. An image processing method according to claim 12, wherein:

the noise removal processing, in which the procedure for referencing nearby pixels in the noise removal processing execute don the band-limited images corresponding to the luminance component and the procedure for referencing nearby pixels in the noise removal processing execute don the band-limited images corresponding to the chrominance component are different from each other, is executed again at least once on each of the plurality of band-limited images having undergone the noise remove processing.

14. An image processing method for removing noise contained in an image, comprising:

extracting a first high-frequency component through first high-pass filter processing executed on the original image;

extracting a second high-frequency component through second high-pass filter processing executed on the extracted first high-frequency component;

extracting a noise component by making a decision as to whether or not the extracted second high-frequency component is greater than a predetermined threshold value; and

removing the noise in the original image based upon the extracted noise component.

25. An image processing method according to claim 14, wherein:

a plurality of high-frequency band-limited images corresponding to the first high-frequency component, the resolution levels of which are lowered in sequence, are generated through ha specific type of band pass filter processing including the first high-pass filter processing, executed on the original image;

the second high-frequency component is extracted from teach of the high-frequency band-limited images by individually executing the second high-pass filter processing on the plurality of high-frequency band-limited images having been generated;

the noise component contained in each of the high-frequency band-limited images is extracted by making a decision as to whether or not the extracted second high-frequency component is greater than a predetermined band-limited images.

16. An image processing method for removing noise contained in an image, comprising:

obtaining the image;

converting the obtained image to an image in a uniform noise space;

extracting a noise component from the converted image in the uniform noise space; and

subtracting the extracted noise component from the converted image in the uniform noise space.

17. An image processing method according to claim 16, wherein:

the noise component is extracted by first extracting a high-frequency component from the converted image in the uniform noise space and then executing nonlinear conversion on the extracted high-frequency component.

18. An image processing method according to claim 17, wherein:

the high-frequency component in each of a plurality of varying frequency bands is individually extracted from the converted image in the uniform noise space;

the noise component in each of the plurality of frequency bands is individually extracted through nonlinear conversion from the extracted high-frequency component in a corresponding frequency band among the plurality of frequency bands; and

the extracted noise component in each of the plurality of frequency bands is subtracted from the converted image in the uniform noise space.

19. (canceled)

20. (canceled)

21. An image processing method for removing noise contained in an image, comprising:

a first step in which an image is obtained;

a second step in which a high-frequency component is extracted from the image;

a third step in which a noise component is extracted from the extracted high-frequency component through nonlinear conversion; and

a fourth step in which a noise-free image is obtained by subtracting the extracted noise component from the image, wherein;

processing in the second step through the fourth step is executed at least once more on the noise-free image obtained in the fourth step in order to obtain a final noise-free image.

22. An image processing method according to claim 21, wherein:

the image is constituted with a chrominance component.