e of two operations at different scales,
   reducing the operation count to a sum of decomposition factors,
   rather than the (un-decomposed) product of factors.
   As always, parsers are provided for a sequence of such operations.

3. Grayscale morphology and rank order filters

   We give an efficient implementation of grayscale morphology for brick
   Sels.  See the Leptonica home page and the source code.

   Brick Sels are separable into linear horizontal and vertical elements.
   We use the van Herk/