Calculation of statistics of one or more images.
Usage: imstat [-nolabel] [-pixstat prefix] [-quiet] image_file ...
  -nolabel        = don't write labels on each file's summary line
  -quiet          = don't print statistics for each file
  -pixstat prefix = if more than one image file is given, then
                     'prefix.mean' and 'prefix.sdev' will be written
                     as the pixel-wise statistics images of the whole
                     collection.  These images will be in the 'flim'
                     floating point format.  [This option only works