ftosh: convert float images to shorts, by RW Cox
Usage: ftosh [options] image_files ...

 where the image_files are in the same format to3d accepts
 and where the options are

  -prefix pname:  The output files will be named in the format
  -suffix sname:  'pname.index.sname' where 'pname' and 'sname'
  -start  si:     are strings given by the first 2 options.
  -step   ss:     'index' is a number, given by 'si+(i-1)*ss'
                  for the i-th output file, for i=1,2,...
              *** Default pname = 'sh'
              *** Default sname = nothing at all
              *** Default si    = 1
              *** Default ss    = 1

  -nsize:         Enforce the 'normal size' option, to make
                  the output images 64x64, 128x128, or 256x256.

  -scale sval:    'sval' and 'bval' are numeric values; if
  -base  bval:    sval is given, then the output images are
  -top   tval:    formed by scaling the inputs by the formula
                  'output = sval*(input-bval)'.
              *** Default sval is determined by finding
                  V = largest abs(input-bval) in all the input
                  images and then sval = tval / V.
              *** Default tval is 32000; note that tval is only
                  used if sval is not given on the command line.