Methods and Systems for Noise Reduction and Image Enhancement

• US 20120062797A1
• Filed: 09/15/2010
• Published: 03/15/2012
• Est. Priority Date: 09/15/2010
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Segall, Christopher A.
• Granted Patent: US 8,600,188 B2
• Time in Patent Office: Days
• US Class Current: 348/606
• CPC Class Codes: G06T 2207/20028 Bilateral filtering
• CPC Class Codes: G06T 2207/20182 Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/75 Unsharp masking
• CPC Class Codes: H04N 5/208 for compensating for attenuation of high frequency components, e.g. crispening, aperture distortion correction
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

Aspects of the present invention are related to systems and methods for image enhancement, wherein an input image may be separated into two images: a first image comprising image content, from the input image, which may be sharpened; and a second image comprising image content, from the input image, which may be attenuated. One aspect of the present invention relates to determining a noise estimate associated with the input image and using the noise estimate to control the separation of the input image into the two images. Another aspect of the present invention relates to controlling the image separation based on the level of sharpening being applied to the first image.

Claims

1. A system for enhancing an input image, said system comprising:

a) an edge-preserving filter for generating, from an input image, a first image comprising image content, from said input image, to sharpen and a second image comprising image content, from said input image, to attenuate; and

b) a noise estimator for determining a noise estimate associated with said input image, wherein a parameter value associated with said edge-preserving filter is based on said noise estimate.

2. The system as described in claim 1, wherein said edge-preserving filter comprises a bi-lateral filter.

3. The system as described in claim 1, wherein said parameter value associated with said edge-preserving filter is proportional to said noise estimate.

4. The system as described in claim 1, wherein said parameter value is a range sigma value.

5. The system as described in claim 4, wherein said range sigma value is proportional to said noise estimate.

6. The system as described in claim 1, wherein said noise estimator comprises:

a) an image-noise statistic estimator for estimating at least one of grain noise, sensor noise and thermal noise in said input image, thereby producing an image-noise statistic;

b) a codec-noise statistic estimator for estimating compression noise in said input image, thereby producing a codec-noise statistic; and

c) a combiner for combining said image-noise statistic and said codec-noise statistic, wherein said noise estimate is based on said combined said image-noise statistic and said codec-noise statistic.

7. The system as described in claim 6, wherein said edge-preserving filter comprises a bi-lateral filter.

8. The system as described in claim 6, wherein said combiner comprises selecting the maximum value of said image-noise statistic and said codec-noise statistic for said combined said image-noise statistic and said codec-noise statistic.

9. The system as described in claim 6, wherein said codec-noise statistic estimator estimates said codec noise statistic from said input image.

10. The system as described in claim 6, wherein said codec-noise statistic estimator estimates said codec-noise statistic from coding parameters associated with said input image.

11. The system as described in claim 10, wherein said codec-noise statistic estimator comprises a plurality of look-up tables, wherein each look-up table in said plurality of look-up tables is associated with a codec and at least one codec coding parameter.

12. The system as described in claim 6 further comprising a decoder for decoding a bitstream associated with said input image.

13. The system as described in claim 6 further comprising:

a) a sharpener for sharpening said first image;

b) an attenuater for attenuating said second image; and

c) an image combiner for combining said sharpened first image and said attenuated second image.

14. The system as described in claim 13 further comprising an up-sampler for up-sampling said combined image.

15. The system as described in claim 13, wherein said sharpener comprises an un-sharp masking filter.

16. The system as described in claim 13 further comprising a sharpening compensator for compensating said combined said image-noise statistic and said codec-noise statistic to account for a level of sharpening associated with said sharpener, and wherein said parameter value associated with said edge-preserving filter is based on said compensated, combined said image-noise statistic and said codec-noise statistic.

17. The system as described in claim 16, wherein:

a) said sharpener comprises an un-sharp masking filter; and

b) said compensating said combined said image-noise statistic and said codec-noise statistic to account for a level of sharpening associated with said sharpener is based on an un-sharp masking alpha parameter value.

18. The system as described in claim 17, wherein said compensating said combined said image-noise statistic and said codec-noise statistic to account for said level of sharpening associated with said sharpener comprises accessing a sharpener look-up table using said un-sharp masking alpha parameter value as an index.

19. The system as described in claim 16 further comprising a temporal filter for combining said compensated, combined said image-noise statistic and said codec-noise statistic with a previous parameter value associated with said edge-preserving filter.

20. The system as described in claim 1 further comprising:

a) a sharpener for sharpening said first image;

b) an attenuater for attenuating said second image; and

c) a combiner for combining said sharpened first image and said attenuated second image.

21. The system as described in claim 20, wherein said sharpener comprises an un-sharp masking filter.

22. The system as described in claim 20 further comprising an up-sampler for up-sampling said combined said sharpened first image and said attenuated second image.

23. The system as described in claim 20 further comprising a sharpening compensator for compensating said combined said image-noise statistic and said codec-noise statistic to account for a level of sharpening associated with said sharpener, and wherein said parameter value associated with said edge-preserving filter is based on said compensated, combined said image-noise statistic and said codec-noise statistic.

24. The system as described in claim 23, wherein:

a) said sharpener comprises an un-sharp masking filter; and

b) said compensating said combined said image-noise statistic and said codec-noise statistic to account for a level of sharpening associated with said sharpener is based on an un-sharp masking alpha parameter value.

25. The system as described in claim 24, wherein said compensating said combined said image-noise statistic and said codec-noise statistic to account for said level of sharpening associated with said sharpener comprises accessing a sharpener look-up table using said un-sharp masking alpha parameter value as an index.

26. The system as described in claim 23 further comprising a temporal filter for combining said compensated, combined said image-noise statistic and said codec-noise statistic with a previous parameter value associated with said edge-preserving filter.