MASK REMOVE

        [ADVANCED\]MASK REMOVE Shape [Arguments ...]

      Remove the specified Shape from the current Mask.  Shape can be
      CIRCLE      Ox Oy Diameter
      ELLIPSE     Ox Oy Major Minor Angle
      RECTANGLE   Ox Oy Major Minor Angle
      POLYGON     File
    where  Ox  Oy are the center of the shapes,  Major and Minor the axes length
    (= side lengths for the Rectangle...) and Angle the Position  Angle  of  the
    Major axis.

    For  the  POLYGON, the  GreG polygon read from the specified File (note that
    this overrides any previous definition of this polygon).