Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!munnari.oz.au!kaukau.comp.vuw.ac.nz!comp.vuw.ac.nz!dsiramd!actrix!jbickers
From: jbickers@actrix.co.nz (John Bickers)
Newsgroups: comp.sys.amiga.tech
Subject: Re: GIF viewer
Summary: Miscellaneous GIF converters
Keywords: GIF
Message-ID: <1990Feb9.231810.19036@actrix.co.nz>
Date: 9 Feb 90 23:18:10 GMT
References: <2758@umbc3.UMBC.EDU>
Reply-To: jbickers@actrix.co.nz (John Bickers)
Distribution: comp.sys.amiga.tech
Organization: Actrix Public Access UNIX, Wellington, New Zealand
Lines: 68

In article <2758@umbc3.UMBC.EDU> jhon@menkar.gsfc.nasa.gov (Jhon Honce) writes:
> So questions:
> 
> 1) What is the limit to the number of colors displayed by the amiga
>    for given modes? (I think HAM and SHAM should do the trick but if
>    I know for sure I wouldn't be asking.)

    Can get up to 64 colors in lo-res, 16 in hi-res, 4096 in HAM. It is also
    possible to get 4096 colors in any mode using one of these dynamic
    palette changing schemes, but this is limited.

    Dynamic schemes are restricted to the mode's normal color limit for each
    scanline.

    Lo-res 64 colors (HALFBRITE) is limited, in that the top 32 colors are
    directly related to the first 32 (half brightness).

    HAM has a problem (see monthly posting for description of HAM) in that
    the translation from 256 "normal" colors can leave color fringing.

> 2) Has anyone had any luck with the GIFtoTMP/TMPtoIFF programs?

    Doesn't SHam (Sliced HAM, from CAR) use this? SHam is the first dynamic
    scheme I've heard of. It works OK for 320x200 pictures.

> 3) Is there a better GIF viewer for the Amiga, and if so, do you know
>    where I could ftp it from?

    There seem to be a lot. The best for 256 color GIFs I have seen so far is
    a program called HamSharp. Anyhow...

        1. HamSharp: resizes very large pictures automatically. Uses decent
            algorithm for mapping 256 colors to HAM, to give very nice
            results. Maybe even better than SHam, which uses a dynamic scheme.

            Only problem noticed so far is it breaks on corrupt pictures.

        2. VirtGIF: never actually seen this one, but the following is quoted
            from Brett Kessler (to someone else):
   "There's a program out there somewhere called VirtGIF that will take
    any GIF picture and put it on the screen.  If it has to, it uses HAM
    mode, and if it's too big for the screen, it lets you scroll around in
    the picture.  If you want, I can send it to you."
            His email addresses are:
           "E-Mail to: consp11@bingvaxu.cc.binghamton.edu
             or try: consp11@bingsuns.pod.binghamton.edu
                   and to: consp11@bingvaxa.BITNET 
                     or on PeopleLink: B.KESSLER"

        3. Giffy, etc: from Compuserve, along with official "docs" for GIF87a.
            Can't handle 256 color pics, but it does work.

        4. Fig, etc: from me, and the 1st NZAmigaUG. Handles any size picture,
            but doesn't automatically resize... that has to be done with
            supplied utilities, which only do basic resizing. Simple color
            algorithm, so output quality is inferior to HamSharp's.

            Handles corrupt files ok. There is also an associated displayer,
            TDis, that will allow you to scroll around very large pics, and
            optionally to do the 3-pixel thing with the left border to keep
            the HAM OK.

    No doubt there are others. The best I've seen though is HamSharp.

> 4) Where can I read about the different display modes for the Amiga?
>    (Then I will be quiet and just read.)

    Hardware reference manual.