Workbench Command is a set of command-line tools that can be used to perform simple and complex operations within Connectome Workbench.
ESTIMATE FWHM SMOOTHNESS OF A VOLUME
   wb_command -volume-estimate-fwhm
      <volume> - the input volume
      [-roi] - use only data within an ROI
         <roivol> - the volume to use as an ROI
      [-subvolume] - select a single subvolume to estimate smoothness of
         <subvol> - the subvolume number or name
      [-whole-file] - estimate for the whole file at once, not each subvolume
         separately
         [-demean] - subtract the mean image before estimating smoothness
      Estimates the smoothness of the input volume in X, Y, and Z directions
      separately, printing the estimates to standard output, in mm as FWHM.  If
      -subvolume or -whole-file are not specified, each subvolume is estimated
      and displayed separately.