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February 2004

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2004.02.23 12:55 "Request for new functions", by Vladimir Pastukhov
2004.02.23 14:50 "Re: Request for new functions", by Frank Warmerdam
2004.02.24 00:28 "Re: Request for new functions", by Vladimir Pastukhov
2004.02.24 07:28 "Re: Request for new functions", by Andrey Kiselev
2004.02.24 07:30 "Re: Request for new functions", by Andrey Kiselev

2004.02.23 14:50 "Re: Request for new functions", by Frank Warmerdam

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,
-- 
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