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Date: Wed, 01 Dec 1999 11:39:04 -0600
To: Tom Kacvinsky <tjk@ams.org>, Andy <apex@calpha.com>
From: "Bryan H. Maret" <homefront@acm.org>
Subject: Re: ZIP compression [was: libtiff 3.5.3 release.]
Cc: tiff@olympiakos.com
In-Reply-To: <Pine.GSO.4.10.9912010938560.29279-100000@sun06.ams.org>
References: <384531D3.DE4F8EB6@calpha.com>
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Libtiff uses a Compression value from the private range for ZIP compression - that's all that Sam could do without Adobe's official blessing. The actual TIFF 7 spec uses a Compression value from the "official" range for Deflate compression. Adobe's ImageReady uses the official value, since its developers had the benefit of the real spec.

regards-
-Bryan Maret (formerly Adobe's TIFF person)
 homefront@acm.org

At 09:42 AM 12/1/99 -0500, Tom Kacvinsky wrote:
>Hi,
>
>As you may or may not know, Adobe's Image Ready support ZIP compressed
>TIFFs (reading and writing), but they use a different tag for the
>compression scheme.  ZIP compressed TIFFs as built by tiffcp cannot be
>opened in Image Ready, and vice versa.  So it lloks like Adobe is
>already heading torwards adding ZIP compression to the TIFF
>specification, but is using a different tag scheme.  I belive that
>Leonard Rosenthal (of Adobe) is on this list and could answer this
>question.
>
>Regards,
>
>Tom
>
>> 
>> What is the compression tag TIFFTAG_COMPRESSION assigned to Zip?  The file
>> tiff.h says
>> #define     COMPRESSION_DEFLATE  32946 /* Deflate compression */
>> An associated tag is Zip quality:
>> /* Note: quality level is on the ZLIB 1-9 scale. Default value is -1 */
>> #define TIFFTAG_ZIPQUALITY  65557 /* compression quality level */
>> 
>
