
   cut buffer <X vector> <Y vector> <X|Y> sx sy nx ny

   take a cut from an image and place it in a pair of vectors.
   the <X vector> gets the pixel coordinate in the given direction,
   the <Y vector> gets the pixel values.  <X|Y> specifies the 
   direction of the cut.  the region sx, sy, nx, ny specifies the
   region for the cut, with summation in the cross-direction.

