Patent ID: 8849064

Claim:
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.