Chagall Reference   Load mask             12.5.93
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   A previously saved 8-bit picture will be loaded
   as a mask over the current picture. This makes
   it possible to create a number of standard masks
   that one can use independently from any particular
   picture.

   Very useful, for instance, are masks that simulate
   a particular material-structure (say paper) or a
   given drawing process (pencil).

   Since masks are stored as halftone pictures in  
   ESM-format, you can modify a mask as easily as
   a picture (and the saved mask can again have a 
   mask of its own applied to it).


