numeric
The alpha transparency of fillstyle. Graphic primitives filled with this fillstyle are made transparent so that underlying graphics are visible. An alpha value is in the range 0 through 1, 1 for fully opaque and 0 for fully transparent (basically making the graphic primitive invisible).
Note: the transparency applies to all components of the fillstyle (color fill, graduation, hatchstyle and/or image tile). If the graphic primitive itself has an alpha transparency defined, then this transparency is applied cumulatively.
The value of this element can be redefined.
The alpha transparency of new fillstyles is 1 by default, unless defined otherwise via the -alph switch on the fillstyle command.