Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!mailrus!iuvax!rutgers!columbia!cunixc!cunixb.cc.columbia.edu!kasdan
From: kasdan@cunixb.cc.columbia.edu (John Kasdan)
Newsgroups: comp.windows.x
Subject: Querying pixels
Message-ID: <2576@cunixc.cc.columbia.edu>
Date: 28 Dec 89 15:46:53 GMT
Sender: news@cunixc.cc.columbia.edu
Reply-To: kasdan@cunixb.cc.columbia.edu (John Kasdan)
Organization: Columbia University
Lines: 28

I have been trying to implement the fast Mandelbrot algorithm on
a VAX 3100 running DECwindows, which I believe to be a version of
X-windows. What I need to do is draw various filled-in circles and
keep track of what points have been filled in. Since the XFillArc
command draws and fills these circles much faster than any algorithm I
have been able to write, I thought I would use the pixels to keep
track of what I have already filled in. The problem is, I can't figure
out how to query a pixel. The only relevant function I've found in
the DEC CD-rom documentation is XGetPixel, which works on images.
Apparently I'm not doing the right thing to get an image from my
display using XGetImage, or something. Can anyone help me with this? I
would appreciate code fragments which I could copy, but suggestions or 
references would also be appreciated.

If this is the wrong forum on which to ask such a question, I
apologize but there are no local gurus known to me and I have no one
else to ask.

_________________
/KAS            
                
John Kasdan             internet: kasdan@cunixd.cc.columbia.edu
Columbia University,    bitnet: kasdan@cunixC.cc.columbia.edu
  School of Law         uucp: 
435 West 116th St.        {rutgers,seismo,topaz}!columbia!cunixd!kasdan
New York, NY 10027
_________________
"Life is like an analogy",  anonymous project leader.