System and method for auto-adjusting image filtering

• US 6,956,582 B2
• Filed: 08/16/2002
• Issued: 10/18/2005
• Est. Priority Date: 08/23/2001
• Status: Expired due to Term

• Current Assignee: Rockwell Collins Simulation and Training Solutions, LLC
• Original Assignee: Evans & Sutherland Computer Corp. (Elevate Entertainment, Inc.)
• Inventors: Tidwell, Reed P.
• Primary Examiner(s): Bella, Matthew C.
• Assistant Examiner(s): Sajous, Wesner
• Application Number:
  US10/222,223
• Publication Number:
  US 20030038818A1
• Time in Patent Office: 1,159 Days
• Field of Search: 345611-615, 345/418, 345421-422, 345/428, 345586-587, 345/589, 345/606, 345/501, 345/530, 345/545, 382/172, 382260-265, 382266-269, 382/274, 382/275, 382/279
• US Class Current: 345/611
• CPC Class Codes: G06T 2200/12 involving antialiasing
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing

Abstract

A method for is provided for antialiasing a computer graphics image using filtering. The method comprises the steps of defining a plurality of regions having samples from pixels in the computer graphics image, where the regions are associated with a pixel of interest and adjacent pixels to form an antialiasing filter. Another step is determining a contrast for each region. A further step is blending the regions that form the filter based on the contrast for each region.

Claims

1. A method for antialiasing a computer graphics image using filtering, the method comprising the steps of:

defining a plurality of regions having samples from pixels in the computer graphics image, where the regions are associated with a pixel of interest and adjacent pixels to form an antialiasing filter;

determining a contrast for each region; and

blending the regions that form the filter based on the contrast for each region by excluding regions from the filter that do not exceed a pre-determined contrast level.

2. A method as in claim 1, wherein the step of defining a plurality of regions further includes the step of including samples from the pixel of interest and adjacent pixels in each of the regions.

3. A method as in claim 1, wherein the step of blending the regions further comprises the step of adjusting the weighting of the samples in each region based on the region'"'"'s contrast.

4. A method as in claim 3, wherein the step of weighting samples based on the region'"'"'s contrast further comprises the step of weighting samples farther from a center of the pixel of interest with an increased weight when the contrast exceeds a pre-determined threshold.

5. A method as in claim 3, wherein the step of weighting samples based on contrast further comprises the step of weighting samples farther from the pixel of interest with a lesser weight when the contrast does not exceed a pre-determnined threshold.

6. A method as in claim 1, wherein the step of blending the regions that form the filter further includes the step of blending the regions which form the filter by increasing region size for regions when the contrast equals or exceeds a pre-determined contrast.

7. A method as in claim 6, wherein the step of increasing region size further includes the step of increasing the number of samples included in the region.

8. A method as in claim 1, wherein the step of blending the regions further includes the step of blending the regions that form the filter by decreasing a region size for regions where the contrast falls below a pre-determined contrast level.

9. A method as in claim 8, wherein the step of decreasing region size further includes the step of decreasing the number of samples included in the region.

10. A method as in claim 1, wherein the step of determining a contrast further comprises the step of determining the contrast by subtracting the sample with the minimum brightness from the sample with the maximum brightness to create a brightness difference.

11. A method as in claim 1, wherein the step of determining the contrast further comprises the step of dividing the sample with the maximum brightness by the sample with the minimum brightness.

12. A method as in claim 1, wherein the step of determining the contrast further comprises the step of dividing the difference between the sample with the maximum brightness and the sample with the minimum brightness by the sample with the maximum brightness.

13. A method for filtering a digital image, comprising the steps of:

defining a plurality of spatial regions that are associated with a pixel of interest, and each spatial region includes samples from adjacent pixels and samples from the pixel of interest;

comparing the intensities of samples in the spatial regions to create a contrast value for each region;

averaging the samples of each spatial region that exceed a pre-defined contrast value; and

replacing the samples of each spatial region that exceed a pre-defined contrast value with the average of the samples.

14. A method as in claim 13, further comprising the step of filtering all the samples in the pixel of interest to create a pixel value.

15. A method as in claim 14, wherein the step of filtering all the samples in the pixel of interest further comprises the step of filtering all the samples in the pixel of interest by averaging the samples to create the pixel value.

16. A method as in claim 13, wherein the step of comparing the intensity of samples further comprises the step of dividing a maximum intensity sample in a region by a minimum intensity sample to produce a contrast ratio.

17. A method as in claim 13, wherein the step of comparing the intensity of samples, further comprises the step of dividing difference between the sample with the maximum brightness and the sample with the minimum brightness by the sample with the maximum brightness to produce a contrast index.

18. A method as in claim 13, wherein in the steps of averaging the samples and replacing the samples of each spatial region with an average of the samples, further comprises the step of averaging the samples and replacing the samples with the average of the samples when the contrast index exceeds 0.5 or the contrast ratio exceeds 2.0.

19. A method for antialiasing computer generated graphic images using a post filter, comprising the steps of:

selecting a pixel of interest;

defining a four corners region associated with a corner of the pixel of interest, and the four corners region includes at least one sample from the pixel of interest and pixels adjacent to the four corners region;

identifying the maximum and minimum intensity sample values in the four corners region;

dividing the maximum intensity sample value by the difference between the maximum and minimum intensity sample values to obtain a contrast ratio;

comparing the contrast ratio to a contrast threshold value;

replacing each sample in the four corners region with the average of the samples in the four corners region when the contrast ratio meets or exceeds the contrast threshold value.

20. A method as in claim 19, further comprising the step of averaging the samples in the pixel of interest to produce a pixel value after the processing on the four corners region has been completed.

21. A method as in claim 19, further comprising the step of repeating the steps above for each of four corners of the pixel of interest.

22. A method as in claim 19, further comprising the step of including at least one sample from each pixel that is adjacent to the corner of the pixel of interest.

23. A method as in claim 22, further comprising the step of including 4 samples in the four corners region where each sample is from a different pixel and one of the samples is from the pixel of interest.

24. A method for filtering a digital image, comprising the steps of:

defining a plurality of spatial regions that are associated with a pixel of interest and each spatial region includes regions from adjacent pixels and the pixel of interest;

comparing the intensity of samples in the spatial regions to create a contrast value;

changing the size of spatial regions based on comparing the contrast value to a pre-defined contrast threshold level;

averaging the samples of each spatial region; and

replacing the samples of each spatial region with average of the samples.

25. A method as in claim 24, wherein the step of changing the size of the spatial regions further includes the step of increasing the size of the spatial regions when the contrast value meets or exceeds the contrast threshold level.

26. A method as in claim 25, wherein the step of increasing the size of the spatial regions further includes the step of increasing the number of samples that are included in the spatial region.

27. A method as in claim 24, wherein the step of changing the size of the spatial regions further includes the step of decreasing the size of the spatial regions when the contrast value is less than the contrast threshold level.

28. A method as in claim 27, wherein the step of decreasing the size of the spatial regions further includes the step of increasing the number of samples that are included in the spatial region.

29. A device for filtering a digital image, comprising:

a pixel buffer to store pixels and associated samples;

a priority encoder, coupled to the pixel buffer, to receive samples for a specific region associated with a pixel and to select samples with the maximum and minimum brightness;

a subtractor coupled to the priority encoder, to subtract the sample with the minimum brightness from the sample with a maximum brightness to create a brightness difference; and

a dividing module associated with the subtractor, to divide the brightness difference by the maximum brightness to create a contrast index;

a comparator coupled to the dividing module to compare the contrast index with a pre-selected contrast index; and

an averaging module to average the samples in a region if the contrast index exceeds the pre-selected contrast index.

30. A device as in claim 29, further comprising a write means to write the average of the samples in a region into each of the samples in the region.