Adaptive edge detection and enhancement for image processing
View Patent ↗The present invention improves image quality by detecting and enhancing edges in an image. Images often include blurry or fuzzy edges that can obscure an image. An edge is a portion of an image separating two regions of substantially constant image intensity. An image can be examined on a pixel-by-pixel basis to find a candidate edge. When a candidate edge is found, a determination can made as to whether the candidate edge is a true edge. A true edge can be enhanced by amplifying the image intensity differences between pixels on the true edge and adjacent pixels not on the true edge. The present invention also provides a novel image processing filter for eliminating well-known noise from an image. The image processing filter can further improve edge enhancement by eliminating such noise prior to the edge detection and enhancement.
1. A method for processing an image, comprising the steps of:
comparing a first image intensity associated with a subject image portion with a second image intensity associated with an adjacent image portion;
determining an image intensity difference between the first image intensity and the second image intensity;
classifying the subject image portion as a candidate edge portion in response to a determination that the first image intensity is less than the second image intensity and a determination that the image intensity difference is greater than a predetermined threshold image intensity difference;
determining whether the adjacent image portion is a non-edge portion;
determining whether the candidate edge portion is a true edge portion the true edge portion having an intensity slope; and,
enhancing the true edge portion by increasing the difference between the true edge portion and the non-edge portion by increasing the intensity slope for the true edge, wherein the third image intensity is less than the first image intensity, thereby sharpening the true edge portion.
2. The method of claim 1 , wherein the step of determining whether the candidate edge portion is a true edge portion, comprises the step of determining whether the candidate edge portion is adjacent to at least one second candidate edge portion.
3. The method of claim 2 , wherein the step of determining whether the candidate edge portion is a true edge portion, further comprises the step of determining whether the candidate edge portion is adjacent to the second candidate edge portion and to a third candidate edge portion.
4. The method of claim 3 , wherein the candidate edge portion, the second candidate edge portion and the third candidate edge portion form a line.
5. The method of claim 1 , wherein the image is a digitized image.
6. The method of claim 5 , wherein the subject image portion is a pixel.
7. The method of claim 5 , wherein the adjacent image portion is a pixel.
8. The method of claim 5 , wherein the image is a frame of a video stream.
9. The method of claim 8 , wherein the image intensity is measured in luminance.
10. The method of claim 8 , wherein the image intensity is measured in luminance and chrominance.
11. The method of claim 1 , wherein the image is an image-type selected from the group consisting of:
animation;
computerized banners;
real-time streaming video;
stored video; and
gaming graphics.
12. A system for enhancing a digitized image, comprising:
a decoder configured to receive an encoded digitized image and to expand the encoded digitized image to generate a decoded digitized image;
a post-processing unit configured to generate a processed image by filtering the decoded digitized image; and
an edge enhancer configured to detect a candidate edge and a non-edge in the processed image, determine if the candidate edge is a true edge or a non-edge, the true edge portion having an intensity slope, and to sharpen the true edge in the processed image by increasing the intensity slope for the true edge wherein the difference between the true edge and the non-edge is increased, thereby sharpening the true edge.
13. The system of claim 12 , wherein the edge is a portion of the decoded digitized image separating a first image portion of substantially uniform image intensity from a second image portion of substantially uniform image intensity.
14. The system of claim 12 , wherein the edge is a line in the decoded digitized image.
15. The system of claim 12 , wherein the edge enhancer is further configured to detect the edge by comparing a subject portion of the decoded digitized image with a first adjacent portion of the decoded digitized image and with a second portion of the decoded digitized image and determining that the subject portion is associated with a lower image intensity level than a first image intensity associated with the first adjacent portion of the decoded digitized image and a second image intensity associated with the second adjacent portion of the decoded digitized image.
16. The system of claim 12 , wherein the post-processor removes an image flaw from the decoded digitized image, in response to a determination that an image intensity of a pixel associated with the image flaw does not differ from at least one surrounding pixel by more than a threshold value.
17. The system of claim 12 , wherein the post-processor adjusts the image flaw in the decoded digitized image, by modifying an image intensity of a pixel associated with the image flaw to correspond to a median image intensity value of at least one surrounding pixel.
18. A method for detecting and enhancing an edge in a decoded digitized image, comprising the steps of:
determining a first image intensity associated with a first pixel in the decoded digitized image;
determining a second image intensity associated with a second pixel in the decoded digitized image;
determining a third image intensity associated with a third pixel in the decoded digitized image;
classifying the first pixel as a first candidate edge pixel in response to a determination that the first image intensity is less than the second image intensity and is less than the third image intensity;
determining whether the first pixel is adjacent to a second candidate edge pixel;
determining whether the second pixel is adjacent to a third candidate edge pixel;
classifying a fourth pixel as a non-edge edge pixel;
classifying the first pixel as a true edge pixel, the true pixel having an intensity slope, in response to a determination that the first pixel is adjacent to the second candidate edge pixel and the second candidate edge pixel is adjacent to the third candidate edge pixel; and
enhancing the true edge pixel by increasing the intensity slope for the true edge wherein the difference between the true edge pixel and the non-edge pixel is increased, thereby sharpening the true edge pixel.
19. The method of claim 18 , further comprising the steps of:
associating a fifth image intensity with the second pixel, the fifth image intensity being higher than the second image intensity; and
associating a sixth image intensity with the third pixel, the sixth image intensity being higher than the third image intensity.
20. The method of claim 18 , further comprising the steps of:
determining a background color associated with the first pixel;
determining a quality level of the digitized image; and
selecting the fourth image intensity based on the background color and the quality level.
21. A method for enhancing a digitized image, comprising the steps of: receiving an encoded digitized image;
expanding the encoded digitized image to generate a decoded digitized image;
generating a processed image by filtering the decoded digitized image; and
detecting a non-edge in the processed image;
detecting a candidate edge in the processed image;
determining if the candidate edge is a true edge or a non-edge, wherein the true edge has an intensity slope;
enhancing the true edge in the processed image by increasing the intensity slope for the true edge wherein the difference between the true edge and the non-edge is increased, thereby sharpening the true edge.
22. The method of claim 21 , wherein the edge is a portion of the decoded digitized image separating a first image portion of substantially uniform image intensity from a second image portion of substantially uniform image intensity.
23. The method of claim 21 , wherein the edge is a line in the decoded digitized image.
24. The method of claim 21 , wherein the step of detecting an edge further comprises comparing a subject portion of the decoded digitized image with a first adjacent portion of the decoded digitized image and with a second portion of the decoded digitized image and determining that the subject portion is associated with a lower image intensity level than a first image intensity associated with the first adjacent portion of the decoded digitized image and a second image intensity associated with the second adjacent portion of the decoded digitized image.
25. The method of claim 21 , further comprising removing an image flaw from the decoded digitized image, in response to a determination that an image intensity of a pixel associated with the image flaw does not differ from at least one surrounding pixel by more than a threshold value.
26. The method of claim 21 , further comprising adjusting an image flaw in the decoded digitized image, by modifying an image intensity of a pixel associated with the image flaw to correspond to a median image intensity value of at least one surrounding pixel.