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From "Dennis E. Hamilton" <>
Subject RE: [DISCUSS] ODF file formats vs Zip
Date Mon, 10 Jun 2013 16:22:47 GMT
Looking into a document having images with WinZip, it appears that GIF and PNG files are not
compressed and SVM files are (with great improvement).  The content.xml files, which can be
megabytes long, benefit greatly from compression (9:1 easily).

Apache OpenOffice 3.4.1 and older versions of will compress the Thumbnail PNG.
 Not sure why, but it is a small file so it shouldn't matter in terms of Save performance.

 - Dennis

PS: I don't know whether uncompressed results are also obtained by attempting compression
and reverting to STORED when the compression is unsuccessful.  Some software does that sort
of thing.  (I have a recollection that DEFLATE can also produce uncompressed sections on discovery
of their uncompressability, but the result won't be the same size as the original.  I don't
know if the DEFLATE compression used will produce those.)

-----Original Message-----
From: Rob Weir [] 
Sent: Monday, June 10, 2013 05:45 AM
To:; Dennis Hamilton
Subject: Re: [DISCUSS] ODF file formats vs Zip

On Sun, Jun 9, 2013 at 4:01 PM, Dennis E. Hamilton
<> wrote:
> Regina is correct about the only two compressions.  As far as I know, there is no way
to control which compression is used.  (If you save with Password, all files are always compressed.)
 Most of the time DEFLATE is used (although there are two files that are not usually compressed,
apparently to make metadata mining simpler for non-encrypted packages).
> There is currently no way to control the compression in AOO.  (The ODF specification
simply stipulates the compression that must be used when compression is done, not whether
compression is done for parts of unencrypted packages.)

Does anyone know whether AOO is smart enough to not waste time trying
to compress already compressed files, like PNG images?  This could
make a big difference in presentations.


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