2012.03.16 14:19 "Re: [Tiff] RFC3949 TIFF-FX support", by Bob Friesenhahn
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.
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.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/