Creating extended depth of field image through focus stacking

This function merges a stack of images taken at multiple focal planes into an all-in-focus image.

This script is a polished version of the codes posted at this link : http://www.magiclantern.fm/forum/index.php?topic=11886.0 It works on the sample dataset found at the link as well. For each dataset, parameter has to be tuned carefully.
Input must be a cell array of images taken at different focal planes, with each cell containing a single color or grayscale image.