Image sharpening with edge direction based undershoot and overshoot reduction

1. An apparatus comprising:

a first circuit configured to (i) receive an image, (ii) generate a sharpened region by sharpening an original region of said image and (iii) generate edge information by detecting an edge in said original region of said image; and

a second circuit configured to (i) receive said image, (ii) compare said original region of said image to said sharpened region to determine whether a sharpening result of a current sample in said original region is an overshoot or an undershoot, (iii) generate a line segment in said original region perpendicular to said detected edge, (iv) determine a result of whether (a) said current sample in said original region is a number of pixels away from said detected edge and (b) said detected edge has a contrast, (v) apply a limit on sharpening said current sample in said original region to generate a final sharpened current sample if the determination of said result is true and, (vi) use said sharpened result of said current sample as said final sharpened current sample if said result is not true, wherein

said contrast is determined based on said line segment,

said line segment is determined based on said edge information; and

said limit applied is selected in response to parameters in a lookup table based on an amount of said overshoot or said undershoot.

2. The apparatus according to claim 1 , wherein said second circuit is further configured to apply said limit based on a direction of said detected edge.

3. The apparatus according to claim 1 , wherein said second circuit is further configured to evaluate said current sample in said original region based on a plurality of neighboring samples in said sharpened region along said line segment.

4. The apparatus according to claim 3 , wherein (i) said second circuit is further configured to evaluate each of said neighboring samples along said line segment as one of a potentially bright sample, a potentially dark sample and a do-not-care sample, and (ii) a change to said current sample is made based on one or more distribution groups of said evaluations of said neighboring samples.

5. The apparatus according to claim 1 , wherein said second circuit is further configured to adjust said current sample in said original region to within a change value from a co-located current sample in said original region.

6. The apparatus according to claim 1 , wherein said second circuit (i) determines said overshoot when said current sample is on a bright side of said line segment and (ii) determines said undershoot when said current sample is on a dark side of said line segment.

7. The apparatus according to claim 1 , wherein said number of pixels is at least two.

8. The apparatus according to claim 1 , wherein said second circuit is further configured to generate said final sharpened current sample to match said original region when the determination of said result is false.

9. The apparatus according to claim 1 , wherein said apparatus forms part of a digital camera.

10. The apparatus according to claim 1 , wherein said line segment defines an integer number of pixels away from the detected edge.

11. The apparatus according to claim 10 , wherein said line segment is defined as a plurality of samples taken at a pixel location adjacent to said detected edge.

12. A method for dynamic image sharpening, comprising the steps of:

generating a sharpened region by sharpening an original region of an image using a circuit;

generating edge information by detecting an edge in said original region of said image;

comparing said original region of said image to said sharpened region to determine whether a sharpening result of a current sample in said original region is an overshoot or an undershoot;

generating a line segment in said original region perpendicular to said detected edge;

determining a result of whether (a) said current sample in said original region is a number of pixels away from said detected edge and (b) said detected edge has a contrast;

applying a limit on sharpening said current sample in said original region to generate a final sharpened current sample if said result is true; and

using said sharpened result of said current sample as said final sharpened current sample if said result is not true,

wherein said contrast is determined based on said line segment, said line segment is determined based on said edge information and said limit applied is selected in response to parameters in a lookup table based on an amount of said overshoot or said undershoot.

13. The method according to claim 12 , wherein said original region is adjusted based on a direction of said detected edge.

14. The method according to claim 12 , wherein an evaluation of said current sample in said original region is based on a plurality of neighboring samples in said sharpened region along a line segment perpendicular to said detected edge.

15. The method according to claim 14 , wherein (i) each of said neighboring samples along said line segment is evaluated as one of a potentially bright sample, a potentially dark sample and a do-not-care sample, and (ii) a change to said current sample is made based on one or more distribution groups of said evaluations of said neighboring samples.

16. The method according to claim 12 , wherein an adjustment of said current sample in said original region is within a change value from a co-located current sample in said original region.

17. The method according to claim 12 , wherein said number of pixels is at least two.

18. The method according to claim 12 , further comprising the step of:

generating said final sharpened current sample to match said current sample when the determination of said result is false.

19. The method according to claim 12 , wherein the steps are performed in a digital camera.