>># 
>># Copyright 1990, 1991 by the Massachusetts Institute of Technology and
>># UniSoft Group Limited.
>># 
>># Permission to use, copy, modify, distribute, and sell this software and
>># its documentation for any purpose is hereby granted without fee,
>># provided that the above copyright notice appear in all copies and that
>># both that copyright notice and this permission notice appear in
>># supporting documentation, and that the names of MIT and UniSoft not be
>># used in advertising or publicity pertaining to distribution of the
>># software without specific, written prior permission.  MIT and UniSoft
>># make no representations about the suitability of this software for any
>># purpose.  It is provided "as is" without express or implied warranty.
>># 
>># $XConsortium: addpxl.m,v 1.5 92/06/11 17:33:00 rws Exp $
>># 
>>#
>>TITLE XAddPixel CH10
>>ASSERTION A XAddPixel-1
A call to XAddPixel adds the value argument to every pixel
in the ximage argument.
>>STRATEGY
For all supported drawables:
   Create a drawable.
   Initialise the drawable's pixels.
   For ZPixmap and XYPixmap:
	   Obtain an ximage from the drawable using XGetImage.
	   Add the drawables depth - 1 to every image pixel using XAddPixel.
	   Verify that the ximage pixels all set correctly using XGetPixel.
