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Date: Fri, 16 Mar 2012 09:19:38 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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Subject: Re: [Tiff] RFC3949 TIFF-FX support
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On Fri, 16 Mar 2012, Steve Underwood wrote:

>> 
>> It seems that we could easily support TIFF-FX tags but my recollection is 
>> that TIFF-FX data needs to be output in a specific order and libtiff does 
>> not provide any such assurance so libtiff is not assured to write TIFF-FX 
>> complaint TIFF.
>> 
>> Bob
> By specific order I assume you are referring to the weird part of TIFF-FX, 
> where a block of tags can be created on a page, using
>
> TIFFTAG_GLOBALPARAMETERSIFD,which apply to all pages.That part can't really

Nothing that exotic.  TIFF-FX (paragraphs 2.1.1 - 2.1.3) says that 
TIFF-FX elements SHOULD be written in a particular ascending linear 
order.  It also recommends that readers SHOULD strive to support 
reading ordinary TIFF, which does not require such ordering.

At one time (and perhaps even now) there were likely FAX devices which 
could transmit from TIFF-FX as long as all the elements were in linear 
order, to avoid the need for additional buffering and seeking. 
Indeed, perfectly written TIFF-FX does not require that the reader 
seek at all, and thus it could be read from something sequential like 
a pipe.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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