  See, for example,
         the code in fmorphgen.1.c and fmorphgenlow.1.c.
         These files were generated by running the program
         prog/fmorphautogen.c. Results can be checked by comparing dwa
         and full image rasterops; e.g., prog/fmorphauto_reg.c.

   Method (b) is considerably faster than (a), which is the
   reason we've gone to the effort of supporting the use
   of this method for all Sels.  We also support two different
   boundary conditions for erosion.

   Similarly, dwa code 