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From: jensen@wrl.dec.com (Paul Jensen)
Newsgroups: comp.sys.dec
Subject: Re: How to get 24-bit pictures on DECstation 5000/200PXG?
Keywords: DECstation 5000 24-bit color images
Message-ID: <1991Feb4.220101.3296@pa.dec.com>
Date: 4 Feb 91 22:01:01 GMT
References: <1991Jan31.172945.1@max.u.washington.edu>
Sender: news@pa.dec.com (News)
Organization: DEC Advanced Technology Development, Palo Alto, CA
Lines: 46

>
>	Please reply via Email; in desparation I am posting to groups which
>I don't normally read!
>
You raise a few points of sufficiently global interest to be worth
posting here.

> [how to  display truecolor images]
The short answer is that what you want to do is fairly simple
with core X (no PEX needed), but may not be necessary unless you enjoy
programming.  Image display software is everybody's favorite first
X program, and as a consequence there are "billions and billions" of
them floating around.  The chances are what you want already exists:
you should check comp.sys.sgi and comp.sources.x.  If you have to
roll your own, write your code to put the image into a matrix of ints
(i.e. 32-bit pixels, 8 each of RGB), then read up on how to use the
XPutImage call.  You can't avoid colormaps, but unless you need
Gamma correction the default on the 24-plane systems will serve you fine.

>- Maybe this has to be done outside of X altogether?
X (+ extensions) is the only way to gain access to the PX[G[-turbo]]
graphics hardware.  The X server uses undocumented driver ioctls() to
gain access to undocumented hardware interfaces.

>- The DEC postscript viewer dxpsview fails on every postscript file I have 
>tried with the X error: "BadAlloc (insufficient resources for operation) 
>			 opcode 53 (X_CreatePixmap)"
>I get the same error on other DECstations (5000/200PX) as well.
>Is this a bug in the Ultrix 4.1 release?  Is there a work-around (maybe
>another more generic X-based postscript viewer)?  
>
This is a "feature", documented in the release notes.  DPS is trying to
create an 8-1/2x11 pixmap; offscreen memory is not tall enough to
accomodate this.  The release notes document a workaround involving the
"watch progress" option (which causes dxpsview to render directly to
the window).  You can also adjust the scale factor (<.9 ought to work)
or orientation (i.e. landscape) menu options.  My favorite is to start
the server with the "-dpi 92" command line option: unlike the other
workarounds, this one lets you say "dxpsview file" without having to
mess around with the menues (92 dpi is closer to the resolution of
most Sony monitors than 100 anyway).

--
					/Paul Jensen
					 Digital Equipment Corp.
					 Palo Alto, CA