Method and system for three-dimensional noise reduction and contrast enhancement of images

1. A method for a camera, comprising:

generating, by an image sensor, a current frame;

receiving, in an image processing pipeline, the current frame from the image sensor;

calculating, in a spatial filtering block of said image processing pipeline, a spatial weight for each pixel s in the current frame, wherein said spatial weight is computed based on a summation of diffused values associated with the pixel s;

selectively filtering, as a step within said image processing pipeline, an intensity I of the pixel s spatially using said spatial weight; and

controlling display of the current frame based on the selective filtering.

2. The method of claim 1 , wherein the diffused values comprise intensity differences between the pixel s and its neighbors in a spatial domain.

3. The method of claim 1 , wherein the diffused values are calculated according to the formula:

T _weight_spatial=Σψ( I ( t,p )− I ( t,s ));

where I represents pixel intensity; and

(t,s) specifies each pixel s in the current frame.

4. The method of claim 3 , wherein filtering the intensity I of the pixel s spatially is according to the formula:

Spatial_filtered_sample= I ( t,s )+λ* T _weight_spatial;

where λ is a constant.

5. The method of claim 4 , wherein selectively filtering the intensity I of the pixel s spatially comprises selecting a constant value rho such that:

ψ( x )=(1−( x /rho){circumflex over ( )}2){circumflex over ( )}2; if | x |<=rho;

ψ( x )=0; if | x |>rho.

6. The method of claim 5 , wherein rho is selected to be proportional to a variance of noise in the current frame.

7. The method of claim 6 , further comprising selectively filtering said intensity temporally based on a temporal weight calculated between the intensity I of the pixel s in the current frame and its value from an immediately preceding frame.

8. The method of claim 7 , wherein the temporal weight is calculated according to the formula:

T _weight_temporal=ψ( I ( t− 1, s )− I ( t,s ));

where I(t, s) is the intensity of the pixel s in current frame; and

I(t−1, s) is its intensity from the immediately preceding frame (t−1).

9. The method of claim 8 , further comprising outputting a temporally filtered pixel calculated in accordance with the following formula:

Temporal_filtered_sample=spatial_filtered_sample+λ* T _weight_temporal;

where λ is a constant.

10. The method of claim 9 , further comprising enhancing contrast in the current frame by applying a contrast enhancement function H(s) to each pixel s with value altered due to the spatial filtering.

11. The method of claim 10 , wherein the contrast enhancement function comprises an edge detection algorithm.

12. An image processing system, comprising:

a lens;

at least one image sensor coupled to the lens, wherein the at least one image sensor is configured to generate a current frame; and

an image processing pipeline, comprising:

a spatial filtering block configured to receive the current frame from the at least one image sensor;

calculate a spatial weight for each pixel s in the current frame, wherein said spatial weight is computed based on a summation of diffused values associated with the pixel s;

selectively filter an intensity I of the pixel s spatially using said spatial weight; and

control display of the current frame based on the selective filtering.

13. The image processing system of claim 12 , wherein the diffused values comprise intensity differences between the pixel s and its neighbors in a spatial domain.

14. The image processing system of claim 12 , wherein the diffused values are calculated according to the formula:

T _weight_spatial=Σψ( I ( t,p )− I ( t,s ));

where I represents pixel intensity; and

(t,s) specifies each pixel s in the current frame.

15. The image processing system of claim 14 , wherein filtering the intensity/of the pixel s spatially is according to the formula:

Spatial_filtered_sample= I ( t,s )+λ* T _weight_spatial;

where λ is a constant.

16. The image processing system of claim 15 , wherein selectively filtering the intensity I of the pixel s spatially comprises selecting a constant value rho such that:

ψ( x )=(1−( x /rho){circumflex over ( )}2){circumflex over ( )}2; if | x |<=rho;

ψ( x )=0; if | x |>rho.

17. The image processing system of claim 16 , wherein rho is selected to be proportional to a variance of noise in the current frame.

18. The image processing system of claim 17 , wherein the method further comprises selectively filtering said intensity based on a temporal weight calculated between the intensity I of the pixel sin the current frame and its value from an immediately preceding frame.

19. The image processing system of claim 18 , wherein the temporal weight is calculated according to the formula:

T _weight_temporal=ψ( I ( t− 1, s )−( t,s ));

where I(t, s) is the intensity of the pixel s in current frame; and

I(t−1, s) is its intensity from the immediately preceding frame (t−1).

20. The image processing system of claim 19 , further comprising outputting a temporally filtered pixel calculated in accordance with the following formula:

Temporal_filtered_sample=spatial_filtered_sample+λ* T _weight_temporal;

where λ is a constant.

21. The image processing system of claim 12 , further comprising a contrast enhancement configured to apply a contrast enhancement function H(s) to each pixel s with value altered due to the spatial filtering.