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Date: Sun, 11 Jan 2009 20:19:15 -0500
From: myopicwatchmaker <myopicwatchmaker@gmail.com>
To: tiff@lists.maptools.org
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Subject: [Tiff] Libtiff compression ratios
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Hi All,
As part of my doctoral thesis work, I produce two and a half terapixels of
grayscale images a month.  As you might imagine, I am eager to minimize the
storage requirements for this data.  Libtiff's support for deflate
compression has served me quite well up until this point.

Recently I noticed that with identical compression settings, Adobe Photoshop
CS2 achieves significantly higher compression ratios than my libtiff
code--producing files that are almost 40% smaller in many cases.

A typical example: I have a 30,000x6500pixel 8-bit grayscale image which,
uncompressed occupies 174Mb on disk.  Libtiff's deflate algorithm compresses
this down to a 66Mb file, where Photoshop produces a 48Mb file.  I save my
images in ~8Mb strips, which appears to be the optimum for zip compression.

Does anyone know why libtiff might fail to match Photoshop's compression
rates?  Are there any paramters in libtiff or libzip that might allow
optimization for humungous images?

Thanks for any input.
Nick

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Hi All,<br>
As part of my doctoral thesis work, I produce two and a half terapixels
of grayscale images a month.&nbsp; As you might imagine, I am eager to
minimize the storage requirements for this data.&nbsp; Libtiff&#39;s support for deflate compression has served me quite well up until
this point.<br>
<br>
Recently I noticed that with identical compression settings, Adobe Photoshop CS2 achieves significantly higher compression ratios than my
libtiff code--producing files that are almost 40% smaller in many cases.<br>
<br>
A typical example: I have a 30,000x6500pixel 8-bit grayscale image
which, uncompressed occupies 174Mb on disk.&nbsp; Libtiff&#39;s deflate
algorithm compresses this down to a 66Mb file, where Photoshop produces a 48Mb file.&nbsp;
I save my images in ~8Mb strips, which appears to be the optimum for
zip compression.<br><br>Does anyone know why libtiff might fail to match Photoshop&#39;s compression rates?&nbsp; Are there any paramters in libtiff or libzip that might allow optimization for humungous images?<br>
<br>
Thanks for any input.<br>
Nick

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