s is
 useful since certain OS handle very large directories (of say &gt;20K
 images) rather poorly (I'm talking to you Bill).  Thus, can take 100K
 images, and write into 5 separate dirs, then read them back in.

 USAGE
   I = imwrite2( I, mulFlag, imagei, path, ...
     [name], [ext], [nDigits], [nSplits], [spliti], [varargin] )

 INPUTS
  I           - image or array or cell of images (if [] reads else writes)
  mulFlag     - set to 1 if I represents a stack of images
  imagei      - first image number
  