Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ukma!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: <1305@cbnewsc.ATT.COM>
Date: 19 Jun 89 20:27:53 GMT
References: <5300015@ux1.cso.uiuc.edu>
Reply-To: vgopal@cbnewsc.ATT.COM (venu.p.gopal)
Organization: AT&T Bell Laboratories
Lines: 30

In article <5300015@ux1.cso.uiuc.edu> phil@ux1.cso.uiuc.edu writes:

>I created a GIF output file using the program FRACTINT.  I then displayed
>that file using different GIF viewers, VGIF, VUGIF, SHWGIF, and FASTGIF.
>All showed DIFFERENT colors.  I thought the color pallette was a part of
>the GIF format.  Can someone explain why different programs show the same
>GIF file in different colors?  Is something defective in the file?

True color representation depends on the graphics display card you are
using.  GIF allows 256 colors, each one of which can be one of 16.7 million
possible colors.  If you are using a CGA, you are limited to 4 colors that
are pre-fixed.  How can you possibly do even a reasonable job on a CGA ?

If you are using an EGA, you have 16 colors that can be selected from
a possible set of 64 colors.  Better, but far from what is needed for
reasonable color representation.

VGA and SuperVGA 256 colors modes are much better.  Though you do not
get the full color resolution that GIF is capable of, you can still
select 256 colors out of 262 thousand colors.  You will find that when
you use these modes, the differences between the display programs
disappear.  The differences mainly exist because the GIF colors
specifications have to be approximated by what the display card can
show and different programs have different methods.

Venu P. Gopal
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