Methods and systems for demosaicing

1. A method for demosaicing an image, said method comprising:

wherein said image comprises a first plurality of pixel locations where at each pixel location, in said first plurality of pixel locations, a first-color-component value and a second-color-component value are known;

wherein said image comprises a second plurality of pixel locations where at each pixel location, in said second plurality of pixel locations, a third-color-component value is known;

wherein no pixel location in said first plurality of pixel locations is in said second plurality of pixel locations;

interpolating, in a first direction, third-color-component values at said first plurality of pixel locations, thereby producing first-direction-interpolated third-color-component values, wherein said interpolating in said first direction comprises a weighted average of a first plurality of third-color-component values and one of a first plurality of first-color-component values and a first plurality of second-color-component values, wherein said one of a first plurality of first-color-component values and a first plurality of second-color-component values is selected based on a first correlation between said first color component and said third color component and a second correlation between said second color component and said third color component;

interpolating, in a second direction, third-color-component values at said first plurality of pixel locations, thereby producing second-direction-interpolated third-color-component values;

interpolating first-color-component values at said second plurality of pixel locations using said first-direction-interpolated third-color-component values when a first criterion comprising a first gradient-strength measure associated with said first direction and a second gradient-strength measure associated with said second direction is met; and

interpolating first-color-component values at said second plurality of pixel locations using said second-direction-interpolated third-color-component values when a second criterion comprising said first gradient-strength measure associated with said first direction and said second gradient-strength measure associated with said second direction is met.

2. A method as described in claim 1 further comprising interpolating first-color-component values at said second plurality of pixel locations using said first-direction-interpolated third-color-component values and said second-direction-interpolated third-color-component values when said first gradient-strength measure associated with said first direction meets a third criterion in relation to said second gradient-strength measure associated with said second direction.

3. A method as described in claim 1 , wherein:

said second plurality of pixels is associated only with said third color component;

said first color component is associated with blue spectral content;

said second color component is associated with red spectral content; and

said third color component is associated with green spectral content.

4. A method as described in claim 1 further comprising median filtering.

5. A method as described in claim 1 further comprising, for a first interpolated first-color-component pixel in said second plurality of pixels:

determining a high-frequency portion of a third-color-component value associated with said first interpolated first-color-component pixel;

determining a low-frequency portion of a first interpolated first-color-component value associated with said first interpolated first-color-component pixel; and

adjusting the first-color-component value of said first interpolated first-color-component pixel to the sum of said high-frequency portion and said low-frequency portion.

6. A method as described in claim 1 further comprising refining a high-frequency portion of one of said first-color-component values, said second-color-component values and said third-color-component values based on another of said first-color-component values, said second-color-component values and said third-color-component values.

7. A method as described in claim 1 further comprising:

interpolating second-color-component values at said second plurality of pixel locations using said first-direction-interpolated third-color-component values when said first gradient-strength measure associated with said first direction meets said first criterion in relation to said second gradient-strength measure associated with said second direction; and

interpolating second-color-component values at said second plurality of pixel locations using said second-direction-interpolated third-color-component values when said first gradient-strength measure associated with said first direction meets said second criterion in relation to said second gradient-strength measure associated with said second direction.

8. A method as described in claim 7 further comprising interpolating second-color-component values at said second plurality of pixel locations using said first-direction-interpolated third-color-component values and said second-direction-interpolated third-color-component values when said first gradient-strength measure associated with said first direction meets a third criterion in relation to said second gradient-strength measure associated with said second direction.

9. A method as described in claim 1 , wherein:

said interpolating first-color-component values at said second plurality of pixel locations using said first-direction-interpolated third-color-component values comprises interpolation in said first direction; and

said interpolating first-color-component values at said second plurality of pixel locations using said second-direction-interpolated third-color-component values comprises interpolation in said second direction.

10. A method for demosaicing an image, said method comprising:

wherein said image comprises a first plurality of pixel locations where at each pixel location, in said first plurality of pixel locations, a first-color-component value and a second-color-component value are known;

wherein said image comprises a second plurality of pixel locations where at each pixel location, in said second plurality of pixel locations, a third-color-component value is known;

wherein no pixel location in said first plurality of pixel locations is in said second plurality of pixel locations;

calculating, in a first direction, a first gradient associated with a third color component, wherein said calculating, in a first direction, a first gradient associated with said third color component comprises a weighted average of one of a first plurality of first-color-component values and a first plurality of second-color-component values, wherein said one of a first plurality of first-color-component values and a first plurality of second-color-component values is selected based on a first correlation between said first color component and said third color component and a second correlation between said second color component and said third color component;

calculating, in a second direction, a second gradient associated with said third color component;

determining a gradient measure using said first gradient and said second gradient;

interpolating, in an interpolation direction determined by said gradient measure, third-color-component values at said first plurality of pixel locations, thereby producing interpolated third-color-component values; and

interpolating first-color-component values at said second plurality of pixel locations using said interpolated third-color-component values.

11. A method as described in claim 10 further comprising interpolating, in said first direction and said second direction, third-color-component values at said second plurality of pixel locations when said gradient measure meets a first criterion.

12. A method as described in claim 10 , wherein:

said second plurality of pixels is associated only with said third color component;

said first color component is associated with blue spectral content;

said second color component is associated with red spectral content; and

said third color component is associated with green spectral content.

13. A method as described in claim 10 further comprising median filtering.

14. A method as described in claim 10 further comprising, for a first interpolated first-color-component pixel in said second plurality of pixels:

determining a high-frequency portion of a third-color-component value associated with said first interpolated first-color-component pixel;

determining a low-frequency portion of a first interpolated first-color-component value associated with said first interpolated first-color-component pixel; and

adjusting the first-color-component value of said first interpolated first-color-component pixel to the sum of said high-frequency portion and said low-frequency portion.

15. A method as described in claim 10 further comprising refining a high-frequency portion of one of said first-color-component values, said second-color-component values and said third-color-component values based on another of said first-color-component values, said second-color-component values and said third-color-component values.

16. A method as described in claim 10 further comprising interpolating second-color-component values at said second plurality of pixel locations using said interpolated third-color-component values.

17. A method as described in claim 16 , wherein said interpolating second-color-component values at said second plurality of pixel locations using said interpolated third-color-component values comprises interpolating in said interpolation direction determined by said gradient measure.

18. A method as described in claim 10 , wherein said interpolating first-color-component values at said second plurality of pixel locations using said interpolated third-color-component values comprises interpolating in said interpolation direction determined by said gradient measure.

19. A method for demosaicing an, said method comprising:

wherein said image comprises a first plurality of pixel locations where at each pixel location, in said first plurality of pixel locations, a first-color-component value and a second-color-component value are known;

wherein said image comprises a second plurality of pixel locations where at each pixel location, in said second plurality of pixel locations, a third-color-component value is known;

wherein no pixel location in said first plurality of pixel locations is in said second plurality of pixel locations;

interpolating, in a first direction, third-color-component values at said first plurality of pixel locations, thereby producing first-direction-interpolated third-color-component values;

interpolating, in a second direction, third-color-component values at said first plurality of pixel locations, thereby producing second-direction-interpolated third-color-component values;

calculating a first gradient measure in said first direction using said first-direction-interpolated third-color-component values;

calculating a second gradient measure in said second direction using said second-direction-interpolated third-color-component values;

determining a preferred interpolation direction using said first gradient measure and said second gradient measure;

interpolating first-color-component values at said second plurality of pixel locations using interpolated third-color-component values associated with said preferred interpolation direction;

interpolating, in a third direction, third-color-component values at said first plurality of pixel locations, thereby producing third-direction-interpolated third-color-component values;

calculating a third gradient measure in said third direction using said third-direction-interpolated third-color-component values; and

wherein said determining a preferred interpolation direction using said first gradient measure and said second gradient measure further comprises using said third gradient measure.