Virtual reality camera

1. A method performed by a computing device having a processor and memory for combining a first frame and a second frame, comprising:

determining by the computing device horizontal and vertical offsets for spatially aligning the first and second frames, comprising summing absolute values of color differences between the first frame and the second frame at a multiplicity of pixel locations, based on trial values for horizontal and vertical offsets;

further determining by the computing device brightness and contrast parameters for chromatically aligning the first and second frames; and

generating by the computing device a panoramic image, comprising compositing a portion of the second frame onto a portion of the first frame, based on the horizontal and vertical offsets and based on the brightness and contrast parameters.

2. The method of claim 1 wherein the summing comprises:

computing partial sums of absolute values of color differences between the first frame and the second frame at pixel locations within horizontal lines, based on the trial values for horizontal and vertical offsets; and

accumulating the partial sums to form a complete sum of absolute values of color differences between the first frame and the second frame at a multiplicity of pixel locations.

3. The method of claim 2 further comprising:

repeating the steps of computing and accumulating for a multiplicity of trial values for horizontal and vertical offsets; and

selecting horizontal and vertical offsets from among the multiplicity of trial values for horizontal and vertical offsets, based on the respective complete sums.

4. The method of claim 3 wherein the selecting selects horizontal and vertical offsets corresponding to a smallest local minimum value from among the complete sums.

5. The method of claim 1 further comprising spatially aligning the first and second frames based on the horizontal and vertical offsets.

6. The method of claim 1 wherein the further determining brightness and contrast parameters comprises calculating means and variances of color values at a multiplicity of pixel locations within the first and second frames.

7. The method of claim 6 wherein the further determining brightness and contrast parameters determines the brightness and contrast parameters in such a way that a mean and variance of color values at multiple pixel locations within the first frame are equal to the respective mean and variance of color values at corresponding multiple pixel locations within the second frame.

8. The method of claim 1 further comprising chromatically aligning the first and second frames based on the brightness and contrast parameters.

9. The method of claim 1 wherein the compositing comprises replacing color values at multiple pixel locations within the first frame with values that are weighted averages of color values in the first frame and color values in the second frame.

10. The method of claim 1 wherein at least one additional frame is combined with the first and second frames, the method further comprising repeating the determining, further determining brightness and contrast parameters and generating at least once for subsequent first and second frames from among the first and second and at least one additional frames.

11. The method of claim 10 further comprising spatially aligning the at least one additional frame with another frame from among the first and second and at least one additional frames, based on the horizontal and vertical offsets.

12. The method of claim 10 further comprising chromatically aligning the at least one additional frame with another frame from among the first and second and at least one additional frames, based on the brightness and contrast parameters.

13. A computer-readable storage medium storing instructions that, when executed, perform a method of combining a first frame and a second frame, the method comprising:

determining horizontal and vertical offsets for spatially aligning the first and second frames by at least summing absolute values of color differences between the first frame and the second frame at multiple pixel locations;

determining brightness and contrast parameters for chromatically aligning the first and second frames; and

generating an image, comprising compositing a portion of the second frame onto a portion of the first frame based on the horizontal and vertical offsets and based on the brightness and contrast parameters.

14. The computer-readable medium of claim 13 further comprising:

computing partial sums of absolute values of color differences between the first frame and the second frame at pixel locations within horizontal lines based on the trial values for horizontal and vertical offsets;

accumulating the partial sums to form a complete sum of absolute values of color differences between the first frame and the second frame at a multiplicity of pixel locations;

repeating the computing and accumulating for multiple trial values for horizontal and vertical offsets; and

selecting horizontal and vertical offsets from among the multiple trial values for horizontal and vertical offsets based on the respective complete sums.

15. The computer-readable medium of claim 13 further comprising spatially aligning the first and second frames based on the horizontal and vertical offsets.

16. The computer-readable medium of claim 13 further comprising chromatically aligning the first and second frames based on the brightness and contrast parameters.

17. A system for combining a first frame and a second frame, comprising:

a processor and memory;

a component configured to determine an offset for spatially aligning the first and second frames by at least summing absolute values of color differences between the first frame and the second frame at multiple pixel locations;

a component configured to determine brightness and contrast parameters for chromatically aligning the first and second frames; and

a component configured to generate an image, comprising compositing a portion of the second frame onto a portion of the first frame based on the offset and based on the brightness and contrast parameters.

18. The system of claim 17 further comprising a component configured to spatially align the first and second frames based on the offset.

19. The system of claim 17 further comprising a component configured to chromatically align the first and second frames based on the brightness and contrast parameters.

20. The system of claim 17 further comprising a component configured to spatially align the first and second frames based on the offset and to chromatically align the first and second frames based on the brightness and contrast parameters.

21. A camera, comprising:

a camera lens;

acquisition circuitry configured to receive images via the camera lens to acquire a first field of view if the camera lens is in a first orientation and to acquire a second field of view if the camera lens is in a second orientation; and

a viewfinder configured to display the second field of view if the camera lens is in the second orientation and to display at least a portion of the first field of view at least partially composited with the second field of view, wherein the portion of the first field of view comprises a section of the first field of view.

22. The camera of claim 21 wherein the section is a strip portion.