METHOD AND DEVICE FOR PROCESSING OF AN IMAGE

• US 20140126834A1
• Filed: 06/19/2012
• Published: 05/08/2014
• Est. Priority Date: 06/24/2011
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Jin, Jian, Chen, Zhibo, Jiang, Wen Fei
• Granted Patent: US 9,292,905 B2
• Time in Patent Office: Days
• US Class Current: 382/266
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement

Abstract

The invention addresses the problem that traditional Total Variation only enforces the horizontal and vertical intensity continuity and thus fails to reconstruct oblique edges well. In an embodiment, Directional Total Variation is defined which supports multiple gradient directions. It first pre-processes the image and determines the direction of edges/texture; Directional TV is calculated based on the gradients along the determined direction and its orthogonal direction. By utilizing adaptive weights to different directions in the regularization, Directional TV is capable of preserving edges independent from their orientation nicely. Thus, Directional TV regularization based image denoising, compression or super resolution tend to obtain better quality.

Claims

1. Method for processing of an image, said method comprising the steps of

pre-processing the image for determining at least one predominant direction of at least one of edges and texture;

determining a total variation of the image using a weighted sum of variations along the at least one predominant direction and along a direction orthogonal to the at least one predominant direction; and

processing the image using regularization of the total variation.

2. Method of claim 1, wherein pre-processing comprises dividing the image into patches and determining a predominant direction for each patch.

3. Method of claim 1, wherein pre-processing comprises calculating gradients for each patch, calculating an energy function for each gradient, calculating a ratio between energy functions of orthogonal gradients, and determining the predominant direction according to the ratio between the energy functions.

4. Method of claim 3, wherein pre-processing comprises determining that the at least one predominant direction has an energy function ratio further exceeding, by at least a predetermined positive threshold, each energy function ratio of gradients in different directions.

5. Method of claim 3, further comprising using the maximal energy function ratio for determining the weights of said weighted sum.

6. Method of claim 2, wherein the step of determining a predominant direction comprises

detecting that a current patch is in a flat region,

detecting that a predominant direction has already been determined for an upper and/or left neighbour patch of the current patch, and

selecting among available possible predominant directions the most similar direction for the current patch.

7. Method according to claim 1, wherein for determining a total variation of the image, the variation along the at least one predominant direction is given higher weight than the variation along a direction orthogonal to the at least one predominant direction.

8. Method according to claim 1, further comprising a step of calculating adaptive weights for said weighted sum of variations along the at least one predominant direction and along a direction orthogonal to the at least one predominant direction, the weights being calculated based on the ratio of energy sums.

9. Method according to claim 8, wherein a first weight α

_i,j that is applied to the variations along the at least one predominant direction x is reverse proportional to the respective energy sum E_x, and a second weight i,j that is applied to the variations orthogonal to the at least one predominant direction is reverse proportional to said energy sum E_x.

10. Method according to claim 1, further comprising steps of

determining for at least one patch that not all of the required gradients are available;

and

calculating the Directional Total Variation by scaling and averaging the determined available gradients for the at least one patch.

11. Device for processing of an image, comprising

a pre-processing unit for pre-processing the image in order to determine at least one predominant direction of at least one of edges and texture;

a Total Variation determining unit for determining a total variation of the image using a weighted sum of variations along the at least one predominant direction and along a direction orthogonal to the at least one predominant direction; and

a processing unit for processing the image using regularization of the total variation.

12. Device according to claim 11, further comprising dividing means for dividing the image into patches, wherein for each patch a predominant direction is determined.

13. Device according to claim 12, wherein the pre-processing unit comprises a calculating and determination unit for calculating gradients for each patch, calculating an energy function for each gradient, calculating a ratio between energy functions of orthogonal gradients, and determining the predominant direction as the one that has a maximum energy function ratio.

14. Device according to claim 12, further comprising a detection and selection unit for detecting that a current patch is in a flat region, detecting that a predominant direction has already been determined for at least one of the upper and left neighbour patch of the current patch, and selecting among available possible predominant directions the most similar direction for the current patch.

15. Device according to claim 11, wherein the Total Variation determining unit comprises calculation means for calculating the Directional Total Variation based on the gradients along the determined at least one predominant direction and its orthogonal direction.