Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!mit-eddie!snorkelwacker!usc!ucsd!ucbvax!pasteur!graft!scott
From: scott@graft.Berkeley.EDU (Scott Silvey)
Newsgroups: comp.windows.x
Subject: XCopyPlane() bug (sort of).
Message-ID: <26023@pasteur.Berkeley.EDU>
Date: 9 Jul 90 22:13:49 GMT
Sender: news@pasteur.Berkeley.EDU
Reply-To: scott@xcf.berkeley.edu
Organization: UC Berkeley Experimental Computing Facility
Lines: 54

I am trying to turn a window's image into an X11 bitmap.  I want to write this
  bitmap out to a file using XWriteBitmapFile().

However, I can't find any way to do this using XCopyPlanes or XGet/PutImage if
  the window is on a color display (multiple planes).  There is apparently 
  no way for me to copy the information from the window to a single plane 
  bitmap short of checking each and every pixel one at a time.  

Here are the two methods I've tried:

1) [XCopyPlane()]  The Xlib manual says that XCopyPlane() doesn't care if the
  depth of it's two drawables is different, however, when I try the following 
  line, XCopyPlane() generates a BadMatch error (Invalid parameter attribues):

  	XCopyPlane(display, 
	     	   window, 			/* 8 bits deep */
             	   bitmap, 			/* 1 bit deep */
		   gc,				/* GC with function GXor */
	    	   0, 0, width, height, 0, 0,	/* width, height == 300 */
  	     	   plane_mask);			/* only 1 bit set */

2) [XGetImage() / XPutImage()]  For XGetImage() on the type XYPixmap, the Xlib
  manual says that the depth of the returned image is equal to the number of
  planes requested in the plane mask.  So, I tried to use XGetImage() and
  XPutImage() with type XYPixmap, but this also generates a BadMatch error:

	image = XGetImage(display, 
			  window, 	       /* 8 bits deep */
			  0, 0, width, height, /* width, height == 300 */
			  plane_mask, 	       /* 1 bit set */
			  XYPixmap);

	XPutImage(display, 
		  bitmap, 		       /* 1 bit deep */
		  gc,  			       /* GC with function GXor */
		  image,  		       /* image from XGetImage */
		  0, 0, 0, 0,  
		  width, height);	       /* width, height == 300 */

The one thing I CAN get to work is to do an XGetImage() and then query each and
  every pixel using XGetPixel.  For each pixel that is not the
background color,
  I do and XDrawPoint() on the bitmap.  This is dog-slow though, doing two
  X operations per pixel (what if I have a megapixel image?!).

It really suprised me to find that there is no supported way to copy data 
  between pixmaps of different depth (or actually from a multiplane pixmap to a
  bitmap).  Am I right this deficiency here?  Or am I missing something
obvious?
  Will there be more support for these sort of operations in future X releases?

Thanks a lot for your help if you answer these questions ...

Scott