Digital camera which estimates and corrects small camera rotations

1. A method of detecting and correcting a small camera rotation in a digital image captured by a portable hand held digital camera, comprising using a processor to perform the steps of:

a) capturing a digital image of a scene using the portable hand held digital camera to provide a captured digital image, wherein the portable hand held digital camera is not held level during the capture of the digital image, being unintentionally positioned at a small rotation relative to the scene;

b) analyzing the captured digital image to detect a set of lines corresponding to horizontal or vertical structures in the scene;

c) computing at least two parameters representing each individual line in the set of lines;

d) determining a rotation angle of the captured digital image responsive to intersection points determined between two or more lines from the set of lines, wherein the intersection points are determined responsive to the parameters representions of the two or more lines from the set of lines, and wherein the magnitude of the rotation angle is less than or equal to 45 degrees and corresponds to the unintentional small rotation relative to the scene;

e) warping the captured digital image based on the rotation angle; and

f) storing the warped digital image.

2. The method claimed in claim 1 , wherein analyzing the captured digital image includes computing gradient information at a number of locations in the captured digital image.

3. The method claimed in claim 1 , further comprising the step of using a gravitational orientation sensor for determining vertical axis of the captured digital image.

4. The method claimed in claim 3 , wherein step d) above uses the vertical axis to determine the rotation angle.

5. The method claimed in claim 1 , wherein the rotation angle and the warped digital image are stored in a memory of the portable hand held digital camera.

6. The method claimed in claim 5 , wherein the rotation angle and the warped digital image are both stored in an image file.

7. The method claimed in claim 1 , further comprising the step of displaying the warped digital image.

8. The method claimed in claim 7 , further comprising the step of employing a user interface to enable a user to select the captured digital image or the warped digital image for storage.

9. The method claimed in claim 7 , further comprising displaying the captured digital image.

10. The method claimed in claim 1 , further comprising the step of determining a vanishing point location from the set of lines.

11. The method claimed in claim 10 , wherein the rotation angle is computed from the vanishing point location.

12. A method of detecting and correcting a small camera rotation in a digital image captured by a portable hand held digital camera, comprising using a processor to perform the steps of:

a) capturing a digital image of a scene using the portable hand held digital camera to provide a captured digital image, wherein the portable hand held digital camera is not held level during the capture of the digital image, being unintentionally positioned at a small rotation relative to the scene;

b) using a gravitational orientation sensor for determining a vertical axis of the captured digital image

c) analyzing the captured digital image to detect a set of lines corresponding to horizontal or vertical structures in the scene;

d) computing at least two parameters representing each individual line in the set of lines;

e) determining a rotation angle of the captured digital image responsive to intersection points determined between two or more lines from the set of lines, wherein the intersection points are determined responsive to the parameters representions of the two or more lines from the set of lines, and wherein the magnitude of the rotation angle is less than or equal to 45 degrees and corresponds to the unintentional small rotation relative to the scene;

f) warping the captured digital image based on the rotation angle and the vertical axis; and

g) storing the modified digital image.

13. The method claimed in claim 12 wherein step e) above uses the vertical axis to determine the small rotation angle.

14. The method claimed in claim 12 , wherein analyzing the captured digital image includes computing gradient information at a number of locations in the captured digital image.

15. The method claimed in claim 12 , wherein analyzing the captured digital image includes detecting a set of lines in the captured digital image.

16. The method claimed in claim 12 , wherein analyzing the captured digital image includes detecting a vanishing point location.

17. A method of detecting and correcting a small camera rotation in a digital image captured by a portable hand held digital camera, comprising using a processor to perform the steps of:

a) capturing a digital image of a scene using the portable hand held digital camera to provide a captured digital image, wherein the portable hand held digital camera is not held level during the capture of the digital image, being unintentionally positioned at a small rotation relative to the scene;

b) analyzing the captured digital image to detect a set of lines corresponding to horizontal or vertical structures in the scene;

c) computing at least two parameters representing each individual line in the set of lines;

d) determining a rotation angle of the captured digital image responsive to intersection points determined between two or more lines from the set of lines, wherein the intersection points are determined responsive to the parameters representions of the two or more lines from the set of lines, and wherein the magnitude of the rotation angle is less than or equal to 45 degrees and corresponds to the unintentional small rotation relative to the scene;

e) warping the captured digital image based on the rotation angle;

f) displaying the warped digital image;

g) employing a user interface to enable a user to select either the captured digital image or the warped digital image for storage; and

h) storing the selected digital image.

18. The method claimed in claim 17 , wherein the user interface enables the user to selectively display either the captured digital image or the modified digital image.

19. The method claimed in claim 17 , wherein analyzing the captured digital image includes detecting a vanishing point location.

20. A portable hand held digital camera comprising:

a) an image sensor for capturing an image of a scene;

b) a first memory for storing the captured image;

c) a processor for analyzing the captured image to:

i) detect a set of lines corresponding to horizontal or vertical structures in the scene;

ii) compute at least two parameters representing each individual line in the set of lines;

iii) determine a rotation angle of the captured image using the set of line responsive to intersection points determined between two or more lines from the detected set of lines, wherein the intersection points are determined responsive to the parameters representions of the two or more lines from the set of lines, and wherein the magnitude of the rotation angle is less than or equal to 45 degrees and corresponds to unintentional small rotations introduced into the digital image when the portable hand held digital camera is not held level during the capture of a digital image, the portable hand held digital camera being unintentionally positioned at a small rotation relative to the scene; and;

iv) provide a warped image based on the rotation angle;

d) a display for displaying the warped image;

e) a user interface for selecting the warped image or the captured image; and

f) a second memory for storing the selected image.