Message-Id: <200201291742.g0THgqg22650@sitelicense.arizona.edu> Date: Tue, 29 Jan 2002 18:28:42 +0100 From: Ithier de Lestrange <mailto:ithier.de.lestrange@GESCO.FR> Subject: Re: Zipping image files To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU
<pre>
Hi,
And did you think about the PNG format. Its a loosy compression format
created to replace GIF to avoid the UNISYS patents problems (the same as the
LZW TIFF). It is also more powerful as it does not have the 256 coulour
limit, it supports alpha channels and gamma correction.
It is one of the three file format (with JPEG and GIF) recognized by all the
browsers (IE and NS).
The specifications are not proprietary (open) and are currently entering the
final stages of ISO/ IEC standardization.
You can find more informations at www.libpng.org and if you want quick
informations http://www.libpng.org/pub/png/pngintro.html
Ithier
-----Message d'origine-----
De : Tim Au Yeung [mailto:mailto:ytau@UCALGARY.CA]
Envoyé : mardi 29 janvier 2002 17:58
À : mailto:IMAGELIB@LISTSERV.ARIZONA.EDU
Objet : Re: Zipping image files
As a couple of other people pointed out, both TIFF and the ZIP format use a
non-lossy compression format -- your gains will be minimal at best if you're
using a compressed TIFF. I can, however, see one argument of when using ZIP
on TIFF files might make sense:
If all of your files are uncompressed TIFF (regardless of type; bitonal,
greyscale, colour, etc.), then for archiving purposes, you only need to
emulate two applications: one for decoding an uncompressed TIFF and one for
unzipping instead of having an application that has to handle multple
compression algorithms. This could simplify archiving -- I believe there's
an open-source version of ZIP (gzip) and the general TIFF format is a
published spec. so both could be implemented in new platforms in the future
relatively easily. Using proprietary algorithms (as could be bundled into
TIFF -- the spec. really doesn't care what compression algorithm you use)
might have implications from an archiving perspective.
Tim
---------
Tim Au Yeung
Manager, Digitization Initiatives
Information Resources
University of Calgary
----- Original Message -----
From: "David Adams" <mailto:David.Adams@NATLIB.GOVT.NZ>
To: <mailto:IMAGELIB@LISTSERV.ARIZONA.EDU>
Sent: Monday, January 28, 2002 12:41 PM
Subject: Zipping image files
>
> Does anyone know if there is any form of change to digital image files by
using WinZIP or 'zipping' applications?
>
> I am interested to know if this will have an affect on TIFF files that are
to be used for long term preservation.
</pre>
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