Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!tut.cis.ohio-state.edu!ucsd!ucsdhub!hp-sdd!andrea
From: andrea@hp-sdd.hp.com (Andrea K. Frankel)
Newsgroups: comp.graphics
Subject: Re: (Sun)PHIGS questions
Message-ID: <3464@hp-sdd.hp.com>
Date: 23 Mar 90 00:22:38 GMT
References: <5276@amelia.nas.nasa.gov>
Reply-To: andrea@hp-sdd.UUCP (Andrea K. Frankel)
Distribution: usa
Organization: Hewlett-Packard, San Diego Division
Lines: 37

In article <5276@amelia.nas.nasa.gov> mckie@amelia.nas.nasa.gov (William McKie) writes:
>By examining clear cgm output files from SunPHIGS programs, it
>appears that when the program selects black as the background
>colour (cgm workstation colour index 0), the cgm output file
>contains no explicit declaration of background colour.  Other
>background colour selections within SunPHIGS result in an
>explicit "BACKCOLR r g b" statement in the cgm file.  Is this
>correct behavior?  I.e. is the default background colour in
>cgm black?  Our cgm translators and displayers appear to
>interpret the default cgm background colour as white, which is
>usually not what we intended when we selected black.

The CGM standard (X3.122-1986) specifies that the default is "device
dependent background colour" for both BACKGROUND COLOUR and index 0 of
the colour table; "device dependent foreground colour" is the default
for index 1.  This was deliberately done so that CRTs could use
white-on-black, and printers could use black-on-white, as their default
colours.

It is up to the implementation of the CGM generator what kind of
assumptions are made about the target device.  You might want to put in
an enhancement request to Sun, asking for a way to specify that the
metafile store the BACKGROUND COLOUR explicitly regardless of its
setting.

You might want to order a copy of the CGM standard from ANSI, so that
you'll be able to tell in the future how much is specified in that
standard, and how much is interpretation and implementation lattitude on
the part of the vendor.

Andrea Frankel, Hewlett-Packard (San Diego Division) (619) 592-4664
	"wake now!  Discover that you are the song that the morning brings..."
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