Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!att!cbnewsc!vgopal
From: vgopal@cbnewsc.ATT.COM (venu.p.gopal)
Newsgroups: comp.graphics
Subject: Re: GIF viewers are inconsistent
Message-ID: <1394@cbnewsc.ATT.COM>
Date: 23 Jun 89 20:06:40 GMT
References: <5300015@ux1.cso.uiuc.edu> <5300017@ux1.cso.uiuc.edu>
Reply-To: vgopal@cbnewsc.ATT.COM (venu.p.gopal)
Organization: AT&T Bell Laboratories
Lines: 42

In article <5300017@ux1.cso.uiuc.edu> phil@ux1.cso.uiuc.edu writes:
..
..So, I'd expect the colors to be truncated this way, and therefore still have
..the same colors displayed on my 256-of-262144 display from a file having
..256-of-16777216 colors.  The colors are instead DRAMATICALLY different.
..One viewer shows one area as several over saturated hues of the rainbow
..and another viewer shows the same thing as a SINGLE ugly green hue.

..> Different display programs also have different default modes. FASTGIF
..> displays GIF files in EGA modes but does a good approximation of better modes
..> using a dithering technique, VGIF uses the VGA modes and I'm unsure
..> about the others. Check the documentation that comes with these programs to
..> see what modes they support and then use the one best suited for YOUR 
..> particular hardware configuration (ie FASTGIF for EGA, VGIF for VGA, ...)
..
..This indeed seems like what must be happening.  Although ALL viewers are
..squishing the images (360x480) into the left side, some were truncating it
..on the bottom, indicating the likelyhood of being in the EGA (640x350) mode.
..
..The FRACTINT program has a tweaked VGA mode of 360x480x256 with non-square
..pixels.  It works by loading the registers directly instead of calling BIOS
..to set a graphics mode (limited choices apparently).  Documentation says this
..works only on IBM VGA *REGISTER COMPATIBLES*.  I'd like to see a viewer that
..can use this mode.  FRACTINT source is available, so why not.  So far, I have
..NO SOURCE to any viewers, so I can't get in and FIX THEM.
..
..--Phil howard--  <phil@ux1.cso.uiuc.edu>

You may want to try VUGIF, posted to c.b.i.p. a short while ago, and
probably available from clarkson, simtel etc. by ftp.

You can select the video mode yourself from the umpteen choices on
the menu and see for yourself what is happening.

It will also scale the picture (if you want) to fit the screen so that
your image size and color quantization effects can be independently seen.

Venu P. Gopal
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