who@portia.Stanford.EDU (Doiknow Liu) (08/31/89)
Newsgroups: comp.graphics
Subject: Fwd:How to get RGB values from XImage data?
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Organization: Stanford University
Keywords: XImage, RGB values, color map
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Hello, netters,
I'm a X-novice and I'm also new to graphics. I need to know how
to get RGB values from the XImage data created by "xwd". This
might be an old question having been discussed before. Sorry if
this is a repetition.
To let you understand better where the problem lies, I'll briefly
describe what I'm doing.
Recently we got a Titan from Ardent Computer Co. Titan is a
supermini graphics computer running under AT&T System V. It
supports X11(R2) window system and a 24-plane DirectColor visual
display , and has a graphics library Dore' built on the top
of X. We have built , using Dore', a dynamic renderer to
simulate a simple battlefield scene consisting of a tank, a
tree, a house and flat "terrain". What we need to do next is to
pass the image to an image processor to extract the
information about the target and track the target.
Ideally I'd like to have the image processor to directly access
the image data stored in the frame buffer(or some other device?
-- I don't quite understand the tigr( Titan graphics hardware )
yet) in order to avoid the overhead incurred in sending
requests(XGetImage)to X server or writing/reading data to/from a
disk file. But accessing frame buffer directly requires quite
lot of understanding of the graphics hardware and I'm hoping
that someday in the near future Ardent will come up with some
solutions.( Can someone on the net shed some light on this
problem ?)
As a first step to pass the pixel data to the image processor, I
used the command level utility -- xclient "xwd" -- to dump an
image to a disk file. Now the problem is how to get pixel RGB
values from the XImage data in the file. Could someone please
tell me how the "((XImage)image)-> data " is REPRESENTED ? Are
there any routines in the public domain that enable me to do the
conversion from the XImage data to RGB values ?
Any suggestions and help would be appreciated.
Stanley J. Lu
School of Aeronautics and Astronautics
Purdue University
West Lafayette, IN 47907
Phone:(317)494-7864
ARPAnet: luj@ecn.purdue.edu
UUCP: pur-ee!luj
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