Method and apparatus for ringing and halo control
View Patent ↗A system is disclosed for reducing artifacts in images and video, such as ringing or halo artifacts. The system may include an edge detector and a gain controller. The edge detector may create an edge image used by the gain controller to create a gain image, and the gain image may be used to reduce artifacts in an image. The gain controller may, for a current pixel in the edge image, compute the maximum value of the edge image over a window containing the current pixel. The gain controller may also perform averaging to determine a maximum edge value and a current edge value, and may also use a ratio of the current edge value and the maximum edge value to determine a gain to be applied to a pixel of an image.
1. A method for reducing an artifact in an image, the method comprising:
detecting edges in the image and creating an edge image;
forming a gain image using the edge image; and
forming a reduced-artifact image using the gain image,
wherein the step of forming the gain image further comprises, for a first pixel of the edge image, steps comprising:
determining a maximum value of the edge image over a window of the edge image comprising the first pixel and at least one other pixel;
performing averaging to determine an average maximum edge value and an average first edge value; and
computing a gain value using a ratio of the average first edge value and the average maximum edge value.
2. The method of claim 1 , wherein the gain image is formed by calculating a gain to be applied to individual pixels in the image.
3. The method of claim 1 , wherein the averaging is shape-adaptive averaging.
4. The method of claim 1 , wherein the step of forming the reduced-artifact image further comprises multiplying pixels of the gain image with pixels of another image.
5. The method of claim 1 , wherein the step of forming the reduced-artifact image further comprises adding pixels of the image to pixels of another image.
6. The method of claim 1 , wherein the step of detecting edges in the image comprises detecting edges in two dimensions.
7. The method of claim 1 , wherein the step of forming the reduced-artifact image operates in two dimensions.
8. The method of claim 1 , wherein the method reduces a ringing or a halo artifact in the image.
9. The method of claim 1 , wherein the image is a portion of another image, a frame of video, or a portion of a frame of video.
10. A device for reducing an artifact in an image comprising:
an edge detector that creates an edge image using the image;
a gain controller that creates a gain image using the edge image; and
an image processor that creates a reduced-artifact image using the gain image,
wherein the gain controller performs, for a first pixel of the edge image, steps comprising:
determining a maximum value of the edge image over a window of the edge image comprising the first pixel and at least one other pixel;
performing averaging to determine an average maximum edge value and an average first edge value; and
computing a gain value using a ratio of the average first edge value and the average maximum edge value.
11. The device of claim 10 , wherein the gain controller creates the gain image by calculating a gain to be applied to individual pixels in the image.
12. The device of claim 10 , wherein the averaging is shape-adaptive averaging.
13. The device of claim 10 , wherein the image processor that creates the reduced-artifact image multiplies pixels of the gain image with pixels of another image.
14. The device of claim 10 , wherein the image processor that creates the reduced-artifact image adds pixels of the image to pixels of another image.
15. The device of claim 10 , wherein the edge detector is a two-dimensional edge detector.
16. The device of claim 10 , wherein the gain controller is a two-dimensional gain controller.
17. The device of claim 10 , wherein the artifact is ringing or a halo effect.
18. The device of claim 10 , wherein the image is a portion of another image, a frame of video, or a portion of a frame of video.
19. The device of claim 10 , wherein the device is a set-top box for cable television, a television, a camera, a video camera, a DVD player, a DVD recorder, or a computer.
20. A non-transitory computer-readable storage medium encoded with instructions that, when executed by a processor, perform a method for reducing an artifact in an image, the method comprising:
detecting edges in the image and creating an edge image;
forming a gain image using the edge image; and
forming a reduced-artifact image using the gain image,
wherein the step of forming the gain image further comprises, for a first pixel of the edge image, steps comprising:
determining a maximum value of the edge image over a window of the edge image comprising the first pixel and at least one other pixel;
performing averaging to determine an average maximum edge value and an average first edge value; and
computing a gain value using a ratio of the average first edge value and the average maximum edge value.
21. The computer-readable storage medium of claim 20 , wherein the gain image is formed by calculating a gain to be applied to individual pixels in the image.
22. The computer-readable storage medium of claim 20 , wherein the averaging is shape-adaptive averaging.
23. The computer-readable storage medium of claim 20 , wherein the step of forming the reduced-artifact image further comprises multiplying pixels of the gain image with pixels of another image.
24. The computer-readable storage medium of claim 20 , wherein the step of forming the reduced-artifact image comprises adding pixels of the image to pixels of another image.
25. The computer-readable storage medium of claim 20 , wherein the step of detecting edges in the image comprises detecting edges in two dimensions.
26. The computer-readable storage medium of claim 20 , wherein the step of forming the reduced-artifact image operates in two-dimensions.
27. The computer-readable storage medium of claim 20 , wherein the method reduces a ringing or a halo artifact in the image.
28. The computer-readable storage medium of claim 20 , wherein the image is a portion of another image, a frame of video, or a portion of a frame of video.