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From: Frank Warmerdam <warmerdam@pobox.com>
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To: Vladimir Pastukhov <vpastukhov@naumen.ru>
Cc: tiff@remotesensing.org
Subject: Re: [Tiff] Request for new functions
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Date: Mon, 23 Feb 2004 09:50:17 -0500
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Vladimir Pastukhov wrote:
> Hello,
> 
> I'm adding Group3 and Group4 TIFF compression support to Python
> Imaging Library, using Libtiff codecs.

Vladimir,

I will leave this issue primarily to Andrey.  However, I have a
few general questions:

  1) Why not just implement all image access (on a block by block basis)
     for PIL with libtiff?   It seems to me there has been a longstanding
     desire for a libtiff based PIL TIFF driver in addition to the existing
     custom one.

  2) If not building a fully libtiff based plugin, why not just adapt
     the codec code you need from libtiff into the pil plugin instead of
     using a full libtiff just for the codecs.

I guess my general concern is that libtiff wasn't really intended to be
a "codec engine" for applications that want to use the codecs in
isolation.  In my own library (GDAL), I needed one of the codecs for
use with a non-TIFF format, but I found it easier to just copy and modify
the codec code I required.

> Because PIL can read image in chunks, calling appropriate decoder,
> it is necessary to save and restore TIFF codec's state.  

Perhaps it is this chunking I don't understand.  Lots of applications
want to read TIFF files in chunks, but libtiff generally requires them
to read a whole strip or block at a time, with a special case for line
by line reading I think.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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