[Image-SIG] Group4 Tiff Decoder?

Glenn Linderman glenn at nevcal.com
Tue May 19 23:05:45 CEST 2009

On approximately 5/19/2009 12:52 PM, came the following characters from 
the keyboard of Greg Taylor:
> Hello all,
> Googling around, I keep seeing mention over the years that PIL has no 
> Group4 tiff decoder. I saw mention of a patch for PIL 1.1.4, but it 
> doesn't look like this ever made it into upstream. Perhaps I haven't 
> dug deep enough, but can anyone enlighten me to what the situation is 
> currently with Group4 Tiff decoding? I'd love to be able to use PIL 
> for some mission critical stuff at work, but this is a show-stopper 
> due to our setup.

I'm currently using command-line ImageMagick and (when on Windows) 
command-line IrfanView (which is way faster than ImageMagick for Group4 
TIFF filse) because PIL doesn't do Group4 decoding or encoding, and 
because the wrapper for direct use of TIFF lib is arcane (which is no 
surprise, because TIFF lib's API is arcane to start with).

What I would dearly like is a simple API that would read a Group4 TIFF 
and convert it to an array of memory bitmaps (one per internal image) in 
a format (a PIL format, or otherwise) that could be manipulated, and 
preferably each array entry converted to/from QtImage format, and 
another API that writes it back out in Group4 TIFF format.

David Boddie provided a source Qt image extension of some sort some time 
back that might do the job, Qt-wise, at least for a single page file, 
but I haven't had time to figure out how to compile my own versions of 
Qt, PyQt, SIP, etc., to figure out how to make that work, nor to figure 
out if it handles multiple page images.

So, this awaits someone providing it, or a large rasher of tuits 
provided, for me to figure out the TIFF lib API and code it myself.

“Everyone is entitled to their own opinion, but not their own facts. In 
turn, everyone is entitled to their own opinions of the facts, but not 
their own facts based on their opinions.” -- Guy Rocha, retiring NV 
state archivist

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