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From: jwz@lucid.com (Jamie Zawinski)
Newsgroups: comp.windows.x
Subject: XImage help
Message-ID: <JWZ.91Apr7030728@thalidomide.lucid.com>
Date: 7 Apr 91 10:07:28 GMT
Sender: usenet@lucid.com
Organization: Lucid, Inc., Menlo Park, CA
Lines: 28

Say I've got an XImage structure that I've read from a file.
What's the best way to display that in a window, when the 
current display doesn't necessarily have the same depth as
the XImage does?  Let's assume the display is at least as
deep as the image.

I am under the (hopefully mistaken!) impression that I have to
do a pixel-by-pixel iteration, copying one image into another,
in order to do do this.  But I can't get that to work either;
this code corrupts the image (slants it, lines too long...)

    new_image = XCreateImage(dpy,
			     DefaultVisual(dpy, scr),
			     DefaultDepth(dpy, scr),
			     ZPixmap, old_image->xoffset,
			     XtMalloc(old_image->bytes_per_line *
				      old_image->height *
				      old_image->depth),
			     old_image->width, old_image->height,
			     old_image->bitmap_pad,
			     old_image->bytes_per_line);
    for (r = 0; r < old_image->height; ++r)
      for (s = 0; s < old_image->width; ++s)
	 XPutPixel (new_image, s, r, XGetPixel(old_image, s, r));

I tried XYPixmap as well, same effect.  What am I doing wrong?

		-- Jamie