Method and apparatus for viewing images

1. A computer-implemented method for viewing images on an interactive computing device comprising:

a) displaying a display image from a stack comprising the display image and at least one compressed sub-image of nominally the same scene, each of said at least one compressed sub-image of said stack having been acquired at respective focal distances;

b) responsive to a user selecting a portion of the display image, mapping said selected portion to a corresponding mapped portion of a sub-image within the stack according to a difference in focal distances between said display image and said sub-image;

c) determining at least one row of compressed image blocks, of the sub-image, extending across the corresponding mapped portion;

d) determining a reference value for a point in a compressed image stream of the sub-image, preceding the at least one row of compressed image blocks;

e) using said reference value, at least partially decoding the at least one row of compressed image blocks of the sub-image; and

f) computing a measure of focus for an area of the corresponding mapped portion coinciding with the decoded image blocks to determine if at least said area of the corresponding mapped portion of the sub-image should be displayed within the display image.

2. A method according to claim 1 comprising repeating steps d) and e) for each of a plurality of rows of image blocks of the sub-image.

3. A method according to claim 1 comprising repeating steps b) to f) for each sub-image of a stack of images.

4. A method according to claim 1 further comprising the steps of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is more in-focus for said area than said display image, displaying said sub-image in place of said display image.

5. A method according to claim 1 further comprising the steps of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is more in-focus for said area than said display image, mapping said area of said sub-image back to a corresponding area of said displayed area and superimposing said mapped area of said sub-image on said displayed area of said display image.

6. A method according to claim 5 further comprising the steps of repeating steps b) to h) for subsequently selected portions of said display image.

7. A method according to claim 5 comprising storing a stack of images in an image file.

8. A method according to claim 7 further comprising replacing said stored display image in said image file with a display image including said superimposed mapped area.

9. A method according to claim 1 further comprising the steps of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is less in-focus for said area than said display image, mapping said area of said sub-image back to a corresponding area of said displayed area and superimposing said mapped area of said sub-image on said displayed area of said display image.

10. A method according to claim 9 further comprising the steps of repeating steps b) to h) for subsequently selected portions of said display image.

11. A method according to claim 1 wherein said computing device is a touch screen device and wherein said selecting is indicated by a user making one of a number of touch gestures on said touch screen.

12. A method according to claim 11 comprising: responsive to a user touching a first portion of the touch screen for an increasing amount of time, increasing the size of said first portion.

13. A method according to claim 1 comprising initially displaying said display image from said stacked images.

14. A method according to claim 1 wherein said image comprises an image within a video stream of images.

15. A method according to claim 1 wherein said images are JPEG images and wherein said image blocks comprise DCT coefficient values, said reference value comprising a DC coefficient.

16. A method according to claim 15 wherein step e) comprises decoding the at least one row of JPEG blocks to provide a set of DCT coefficient values for said at least one row of blocks; and wherein step f) comprises computing said measure of focus as a function of the DCT coefficient values.

17. A method according to claim 1 wherein said images are stored in YUV format and step e) comprises at least initially only decoding Y data for said at least one row of image blocks.

18. A method according to claim 1 further comprising the step of dividing said selected portion of the display image into a plurality of sub-portions and performing steps c) to f) for each sub-portion.

19. A method according to claim 1 wherein said mapping is based on a difference in magnification factor determined according to a difference in focal distance between said display image and said sub-image.

20. A method according to claim 19 further comprising obtaining a respective global alignment indicator for each pair of images in the stack and wherein said mapping includes correcting for said alignment before determining said corresponding mapped portion.

21. A method according to claim 1 operating in a digital image acquisition device.

22. A method according to claim 1 operating in a computing device arranged to receive said image from a digital image acquisition device, said computing device being arranged to either acquire or determine said mapping based on the focal distances used to acquire the images of said stack.

23. An interactive computing device comprising a processor and a display, the processor arranged to perform the steps of:

a) displaying a display image from a stack comprising the display image and at least one compressed sub-image of nominally the same scene, each of said at least one compressed sub-image of said stack having been acquired at respective focal distances;

b) responsive to a user selecting a portion of the display image, mapping said selected portion to a corresponding mapped portion of a sub-image within the stack according to a difference in focal distances between said display image and said sub-image;

c) determining at least one row of compressed image blocks, of the sub-image, extending across the corresponding mapped portion;

d) determining a reference value for a point in a compressed image stream of the sub-image, preceding the at least one row of compressed image blocks;

e) using said reference value, at least partially decoding the at least one row of compressed image blocks of the sub-image; and

f) computing a measure of focus for an area of the corresponding mapped portion coinciding with the decoded image blocks to determine if at least said area of the corresponding mapped portion of the sub-image should be displayed within the display image.

24. An interactive computing device of claim 23 , wherein the processor is further arranged to repeat the steps d) and e) for each of a plurality of rows of image blocks of the sub-image.

25. An interactive computing device of claim 23 , wherein the processor is further arranged to repeat the steps b) to f) for each sub-image of a stack of images.

26. An interactive computing device of claim 23 , wherein the processor is further arranged to perform the step of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is more in-focus for said area than said display image, displaying said sub-image in place of said display image.

27. An interactive computing device of claim 23 , wherein the processor is further arranged to perform the step of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is more in-focus for said area than said display image, mapping said area of said sub-image back to a corresponding area of said displayed area and superimposing said mapped area of said sub-image on said displayed area of said display image.

28. A non-transitory, tangible computer readable storage medium comprising executable instructions which when executed in an interactive computing device are arranged to perform the steps of:

a) displaying a display image from a stack comprising the display image and at least one compressed sub-image of nominally the same scene, each of said at least one compressed sub-image of said stack having been acquired at respective focal distances;

b) responsive to a user selecting a portion of the display image, mapping said selected portion to a corresponding mapped portion of a sub-image within the stack according to a difference in focal distances between said display image and said sub-image;

c) determining at least one row of compressed image blocks, of the sub-image, extending across the corresponding mapped portion;

d) determining a reference value for a point in a compressed image stream of the sub-image, preceding the at least one row of compressed image blocks;

e) using said reference value, at least partially decoding the at least one row of compressed image blocks of the sub-image, and

f) computing a measure of focus for an area of the corresponding mapped portion coinciding with the decoded image blocks to determine if at least said area of the corresponding mapped portion of the sub-image should be displayed within the display image.

29. A non-transitory, tangible computer readable storage medium of claim 28 , comprising additional executable instructions which, when executed in the interactive computing device, are arranged to repeat the steps d) and e) for each of a plurality of rows of image blocks of the sub-image.

30. A non-transitory, tangible computer readable storage medium of claim 28 , comprising additional executable instructions which, when executed in the interactive computing device, are arranged to repeat the steps b) to f) for each sub-image of a stack of images.

31. A non-transitory, tangible computer readable storage medium of claim 28 , comprising additional executable instructions which, when executed in the interactive computing device, are arranged to perform the step of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is more in-focus for said area than said display image, displaying said sub-image in place of said display image.

32. A non-transitory, tangible computer readable storage medium of claim 28 , comprising additional executable instructions which, when executed in the interactive computing device, are arranged to perform the step of:

h) responsive to said focus measure for said area of the corresponding mapped portion indicating said sub-image is more in-focus for said area than said display image, mapping said area of said sub-image back to a corresponding area of said displayed area and superimposing said mapped area of said sub-image on said displayed area of said display image.