stack_greedy: Paul's histology stack to MRI registration implementation
Usage:
  stack_greedy volmatch [cmd_options] <project_dir>
Required Command Options:
  -i <image>             : 3D image to use as target of registration
Additional Command Options:
  -gm <image>            : A mask image for the 3D image. Metric and gradient will
                           only be computed over the mask
Options Shared with Greedy (see Greedy docs for more info):
  -m metric              : Metric to use for slice matching
  -n NxNxN               : Number of iterations per level of multi-res
  -threads N             : Number of allowed concurrent threads
  -gm-trim <radius>      : Generate mask for gradient computation 
  -search N s_ang s_xyz  : Random search over rigid transforms 
