Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!bloom-beacon!dont-send-mail-to-path-lines
From: mouse@lightning.mcrcim.mcgill.EDU (der Mouse)
Newsgroups: comp.windows.x
Subject: Re:  Remembering Graphics
Message-ID: <9103230541.AA03161@lightning.McRCIM.McGill.EDU>
Date: 23 Mar 91 05:41:06 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 41

> We have 16 bit grayscale images that we sample down to 8 bit images
> based on a particular (and changable) window/level setting into a
> Pixmap that is then CopyArea'd onto a Window.  All graphics
> (text,lines etc..) are drawn into the Pixmap and then re-CopyArea'd
> onto the window.  This enables taking care of Expose events for those
> windows that have images and graphics.

> Our problem is when we re-sample the 16 bit image into the Pixmap
> (which is often and can occur almost anywhere in our program) all of
> the text/lines are then gone [...].

[8-bit PseudoColor hardware]

> - We do not want to limit the number of bits in the colormap by, say,
>   1 bit and use plane masks [...].
> - We have thought about have text/lines in one Pixmap and the image
>   in another Pixmap and then combining them together when a window is
>   Exposed.

You could keep a bitmap that is, say, 0 where the image is to appear
and 1 where the annotations are to appear, then keep two pixmaps, one
for the picture and one for the annotations, using the bitmap as a
clip-mask when copying things to make sure you don't destroy more than
you want to.

If you are willing to require the server to support SHAPE (not
unreasonable IMO) and the annotations don't change often, you could
keep them in a separate window, shaped to fit them precisely, thus
sidestepping the problem entirely.

You could put the image in the window's background pixmap, then draw
the annotations as graphics; then the server deals with refreshing the
image for you, and you just need to redraw the annotations on expose.

There are probably other ways, but those are all that come to mind
right now.

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu