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From: kall@mayo.EDU (Bruce Kall)
Newsgroups: comp.windows.x
Subject: Remembering Graphics
Message-ID: <9103211805.AA00981@neuro_dev.mayo.EDU>
Date: 21 Mar 91 18:05:25 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 34


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
because they were never in the 16 bit image but only in the Pixmap/Window.

How could we 'remember' the text/lines that were in the Pixmap and hence on
the window when all we want to do is remap the image (obviously a graphics
overlay plane would alleviate the problem.  This is a 8-bit Sun display).

- We do not want to limit the number of bits in the colormap by, say, 1 bit and
use plane masks to essentially, write protect the text in that bit
since this would leave us with only 128 gray levels instead of 256.
- 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.  None of
the GC functions seem to be correct to do this.  We use colormap locations
0-8 for colors and 9-256 for the grayscale image.

Does anyone have any suggestions??



\------------------------------------------------------------\
 \   Bruce Kall                \  Internet:   Kall@Mayo.edu   \
  \   Mayo Clinic (Foundation)  \  Phone: (507)-255-4768       \
   \   Rochester, MN 55905       \                              \
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