Systems and methods for chroma noise reduction

• US 9,710,896 B2
• Filed: 07/10/2015
• Issued: 07/18/2017
• Est. Priority Date: 05/31/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Lim, Suk Hwan, Zimmer, Mark
• Primary Examiner(s): COUSO, YON JUNG
• Application Number:
  US14/796,916
• Publication Number:
  US 20150317772A1
• Time in Patent Office: 739 Days
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing

Abstract

Systems and methods for reducing chrominance (chroma) noise in image data are provided. In one example of such a method, image data in YCC format may be received into logic of an image signal processor. Using the logic, noise may be filtered from a first chrominance component or a second chrominance component, or both, of the image data, using a sparse filter and a noise threshold. The noise threshold may be determined based at least in part on two of the components of the YCC image data.

Claims

1. A method comprising:

receiving image data in YCC format into logic of an image signal processor; and

using the logic to filter noise from a first chrominance component or a second chrominance component, or both, using a sparse filter and a noise threshold, wherein the noise threshold is determined based at least in part on two of the components of the image data, and wherein the sparse filter comprises a plurality of zeros employed as filter coefficients configured to avoid sampling a portion of the image data.

2. The method of claim 1, wherein the image data is received in a YCC 4:

2;

0 format to effectively increase a spatial resolution of the sparse filter.

3. The method of claim 1, wherein the image data is received in a YCbCr format.

4. The method of claim 1, wherein the sparse filter is configured to filter a pixel kernel of 11Hx9V or larger.

5. The method of claim 1, wherein the sparse filter is configured to filter a pixel kernel using line buffer folding.

6. The method of claim 1, wherein the noise threshold is determined by indexing a luminance (Y) component and the first chrominance component in a 2D lookup table.

7. The method of claim 1, wherein the noise threshold is determined by indexing the luminance (Y) component and the second chrominance component in a 2D lookup table.

8. The method of claim 1, wherein the noise threshold is determined by indexing the first chrominance component and the second chrominance component in a 2D lookup table.

9. An electronic device comprising:

an imaging device configured to obtain raw image data; and

image signal processing circuitry configured to;

process the raw image data to obtain RGB image data;

process the RGB image data to obtain YCC image data; and

filter the YCC image data to remove chroma noise from a first chroma component of the YCC image data based at least in part on a first noise threshold provided by a first 2D lookup table of noise thresholds, wherein the first 2D lookup table of noise thresholds is indexed according to a first index value and a second index value.

10. The electronic device of claim 9, wherein the image signal processing circuitry is configured to determine the first noise threshold by indexing the first 2D lookup table with the luminance (Y) component as the first index value and the first chroma component as the second index value.

11. The electronic device of claim 9, wherein the image signal processing circuitry is configured to determine the first noise threshold by indexing the first 2D lookup table with the luminance (Y) component as the first index value and a second chroma component as the second index value.

12. The electronic device of claim 9, wherein the image signal processing circuitry is configured to determine the first noise threshold by indexing the first 2D lookup table with the first chroma component as the first index value and a second chroma component as the second index value.

13. The electronic device of claim 9, wherein the image signal processing circuitry is configured to filter the YCC image data using programmable filter coefficients of either 0 or 1.

14. The electronic device of claim 9, wherein the image signal processing circuitry is configured to filter the YCC image data to remove chroma noise from a second chroma component based at least in part on a second noise threshold provided by a second 2D lookup table of noise thresholds.

15. An image signal processing system comprising:

a YCC-format image processing pipeline comprising a plurality of processing blocks, wherein the YCC-format image processing pipeline comprises;

chroma noise reduction circuitry configured to reduce chroma noise in a first chroma component or a second chroma component of a pixel of interest in YCC image data using a sparse filter and a noise threshold, wherein the noise threshold is determined based at least in part on two components of the YCC image data, wherein the sparse filter comprises a plurality of zeros employed as filter coefficients configured to avoid sampling a portion of the YCC image data.

16. The image signal processing system of claim 15, wherein the chroma noise reduction circuitry is configured to:

process the image data to obtain RGB image data;

process the RGB image data to obtain YCC image data; and

filter the YCC image data to remove the chroma noise from the first chroma component or the second chroma component of the YCC image data.

17. The image signal processing system of claim 16, wherein the chroma noise reduction circuitry is configured to fiter the YCC image data based at least in part on the noise threshold provided by a 2D lookup table of noise thresholds.

18. The image signal processing system of claim 17, wherein the chroma noise reduction circuitry is configured to determine the noise threshold by indexing the 2D lookup table with a luminance (Y) component and the first chroma component or the second chroma component.

19. The image signal processing system of claim 15, wherein the YCC-format image processing pipeline comprises scaling circuitry configured to scale the YCC image data, wherein the chroma noise reduction logic is configured to take place after scaling.

20. The image signal processing system of claim 15, wherein the YCC-format image processing pipeline comprises scaling circuitry configured to scale the YCC image data, wherein the chroma noise reduction logic is configured to take place before scaling.