Method and system for reducing mosquito noise in a digital image
View Patent ↗A method and system is provided for reducing mosquito noise in a digital image. The method and system receives an input luminance value for a first pixel in the digital image, and determines whether the first pixel is in relative close proximity to an object appearing in the digital image, based on a comparison of the variation between the input luminance value for the first pixel and luminance values of a first plurality of neighboring pixels. If the first pixel is in relative close proximity to an object, the method performs an average filtering of the input luminance value for the first pixel, based on the luminance values of a second plurality of neighboring pixels, to provide a filtered luminance value for the first pixel.
1. A method for reducing mosquito noise in a digital image, comprising:
receiving an input luminance value for a first pixel in the digital image;
determining whether the first pixel is in relative close proximity to an object appearing in the digital image, based on a comparison of the variation between the input luminance value for the first pixel and luminance values of a first plurality of neighboring pixels; and
if the first pixel is in relative close proximity to an object, performing an average filtering of the input luminance value for the first pixel, based on the luminance values of a second plurality of neighboring pixels different from the first plurality of neighboring pixels, to provide a filtered luminance value for the first pixel.
2. The method of claim 1 wherein the method determines whether the pixel is in relative close proximity to an object by calculating a maximum variation between the luminance value of the first pixel and the luminance values of the first plurality of neighboring pixels.
3. The method of claim 2 wherein the first plurality of neighboring pixels reside within an M×N window surrounding the pixel.
4. The method of claim 3 wherein the first plurality of neighboring pixels reside within an 9×14 window surrounding the pixel.
5. The method of claim 1 further comprising:
calculating a blending value, based on a comparison of the variation between the luminance value for the first pixel and luminance values of the first plurality of neighboring pixels; and
determining an output luminance by blending the filtered luminance value for the first pixel and the input luminance value of the first pixel, based on the blending value.
6. The method of claim 5 wherein the blending value is proportional to a maximum variation between the luminance value of the first pixel and the luminance values of the first plurality of neighboring pixels.
7. The method of claim 1 wherein the average filtering is an adaptive average filtering.
8. The method of claim 7 wherein the second plurality of neighboring pixels reside within a 3×3 window surrounding the first pixel.
9. A method for reducing mosquito noise in a digital image, comprising:
selecting a first pixel in the digital image;
calculating a maximum variation between the luminance value of the first pixel and the luminance values of a first plurality of neighboring pixels;
determining whether the first pixel is in relative close proximity to an object appearing in the digital image, by comparing the maximum variation to a first threshold value; and
if the first pixel is in relative close proximity to an object, performing adaptive average filtering of the luminance value for the first pixel, based on the luminance values of a second plurality of neighboring pixels different from the first plurality of neighboring pixels, to provide a filtered luminance value for the first pixel.
10. The method of claim 9 , further comprising:
comparing the maximum variation to a second threshold value to generate a blending value; and
determining an output luminance by blending the filtered luminance value for the first pixel and the input luminance value of the first pixel, based on the blending value.
11. The method of claim 10 wherein the output luminance is determined according to the following equation:
Y ″( i,j )= Y ′( i,j )×alpha_obj( i,j )+ Y ( i,j ) (1−alpha_obj( i,j ))
where V′(i,j) is the output luminance for the first pixel, Y′(ij) is the filtered luminance value, Y(i,j) is the input luminance value and alpha_obj(ij) is the blending value.
12. The method of claim 11 wherein alpha_obj(i,j) is equal to “0” when the maximum variance is less than or equal to the first threshold value, “1” when the maximum variance is greater than or equal to the second threshold value, and otherwise is equal to a value between 0 and 1 that is proportional to the maximum variance.
13. The method of claim 11 wherein the first plurality of neighboring pixels reside within an M×N window surrounding the pixel.
14. The method of claim 11 wherein Y′(ij) is calculated according to the following equations:
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where c(i,j) is a predetermined coefficient of the second plurality of neighboring pixels, Y(i,j) is the input luminance of pixel (i,j), a (i,j) is a correlation between the first pixel and the second plurality of neighboring pixels, REG_TH 1 and REGTH 2 are predetermined threshold values, and m×n is a filter window size corresponding to the second plurality of neighboring pixels.
15. A system for reducing mosquito noise in a digital image, comprising:
an object detection module that receives an input luminance value for a first pixel in the digital image and determines whether the first pixel is in relative close proximity to an object appearing in the digital image, based on a comparison of the variation between the input luminance value for the first pixel and luminance values of a first plurality of neighboring pixels; and
a filtering module that performs an average filtering of the input luminance value for the first pixel, based on the luminance values of a second plurality of neighboring pixels different from the first plurality of neighboring pixels, to provide a filtered luminance value for the first pixel if the first pixel is determined to be in relative close proximity to an object.
16. The system of claim 15 wherein the object detection module determines whether the pixel is in relative close proximity to an object by calculating a maximum variation between the luminance value of the first pixel and the luminance values of the first plurality of neighboring pixels.
17. The system of claim 16 wherein the first plurality of neighboring pixels reside within an M×N window surrounding the pixel.
18. The system of claim 15 wherein the object detection module calculates a blending value, based on a comparison of the variation between the luminance value for the first pixel and luminance values of the first plurality of neighboring pixels, and wherein the system further comprising
circuitry for determining an output luminance by blending the filtered luminance value for the first pixel and the input luminance value of the first pixel, based on the blending value.
19. The system of claim 18 wherein the output luminance is determined using the following equation:
Y ″( i,j )= Y ′( i,j )×alpha_obj( i,j )+ Y ( i,j ) (1−alpha_obj( i,j ))
where Y″(i,j) is the output luminance for the first pixel, Y′(ij) is the filtered luminance value, Y(i,j) is the input luminance value and alphaobj(ij) is the blending value.
20. The system of claim 19 wherein alpha_obj(i,j) is equal to “0” when the maximum variance is less than or equal to the first threshold value, “1” when the maximum variance is greater than or equal to the second threshold value, and otherwise is equal to a value between 0 and 1 that is proportional to the maximum variance.
21. The system of claim 20 wherein Y′(iJ) is calculated according to the following equations:
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where c(i,j) is a predetermined coefficient of the second plurality of neighboring pixels, Y(i,j) is the input luminance of pixel (i j), a (i,j) is a correlation between the first pixel and the second plurality of neighboring pixels, REGTH 1 and REGTH 2 are predetermined threshold values, and m×n is a filter window size corresponding to the second plurality of neighboring pixels.
22. The system of claim 15 wherein the first plurality of neighboring pixels is larger than the second plurality of plurality of neighboring pixels.
23. The system of claim 15 wherein the object detection module and filtering module are operatively disposed within a digital television chip.