>># 
>># 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: sbimg.m,v 1.5 92/06/11 17:42:37 rws Exp $
>># 
>>#
>>TITLE XSubImage CH10
>>ASSERTION A XSubImage-1
When the rectangle specified by the x, y, subimage_width
and subimage_height arguments is contained in the image
ximage, then a call to XSubImage creates a copy of the
subimage and returns a pointer to the newly created
subimage.
>>STRATEGY
For all supported drawables types:
   Create a drawable.
   Initialise the drawable.
   For XYPixmap and ZPixmap:
      Create an image using XGetImage.
      Obtain a subimage using XSubImage.
      Verify that the pixels in the subimage are correctly set using XGetPixel.
