LibTiff Mailing List

Peter Smith <psmith@creo.com> writes:
> I would lay the blame for this inconsistency in viewer behaviour on the 
> Tiff 6.0 spec itself, which states:
>
> "[The Orientation tag] is recommended for private (non-interchange) use 
> only.  Most images are scanned and stored in the Orientation = 1 format, 
> and most TIFF readers can only handle this case."
>
> It makes me wonder why this tag was even included in the spec.

TIFF has always been designed on the principle that the writer can write
anything he damn pleases, and perhaps the reader will be able to make
sense of it.  Look through the spec: surely 75% of it describes features
that a run-of-the-mill reader would be unable to cope with.  (Show me
a reader that will do something sensible with YCbCr, associated-alpha,
32-bit-float-sample images ... to take just one example.  If you say
your code can handle that nicely, I'll start asking about tiles,
padding, downsampling, and planar configuration.)

I think the spec is being quite honest here to tell you what part of
the described feature set is actually likely to be portable.

If this approach to compatibility doesn't thrill you, perhaps you
should consider another file format.  For instance, PNG, which was
designed in large part on the principle that TIFF blew this issue
badly.  The PNG spec expects that every reader should be able to
do something sensible with every PNG file, which is certainly not
the design assumption of TIFF.  On the other hand, you can't stick
a YCbCr, associated-alpha, 32-bit-float-sample image into a PNG.
You pays your money and you takes your choice...

			regards, tom lane
			organizer, Independent JPEG Group
			member, PNG development group
			onetime member, TIFF advisory committee


AWARE [SYSTEMS]		Imaging expertise for the Delphi developer
		TIFF and LibTiff Mailing List Archive
	LibTiff Mailing List TIFF and LibTiff Mailing List Archive March 2002 Previous Thread Next Thread Previous by Thread Next by Thread Previous by Date Next by Date Contact The TIFF Mailing List Homepage This list is run by Frank Warmerdam Archive maintained by AWare Systems	Thread 2002.03.20 16:37 "Changing Orientation Tag", by Erika Nesse 2002.03.22 05:56 "Re: Changing Orientation Tag", by Jon Saxton 2002.03.22 21:13 "Re: Changing Orientation Tag", by Peter Smith 2002.03.23 05:38 "Re: Changing Orientation Tag", by Tom Lane 2002.03.25 14:05 "Re: Changing Orientation Tag", by Erika Nesse 2002.03.23 05:38 "Re: Changing Orientation Tag", by Tom Lane Peter Smith <psmith@creo.com> writes: > I would lay the blame for this inconsistency in viewer behaviour on the > Tiff 6.0 spec itself, which states: > > "[The Orientation tag] is recommended for private (non-interchange) use > only. Most images are scanned and stored in the Orientation = 1 format, > and most TIFF readers can only handle this case." > > It makes me wonder why this tag was even included in the spec. TIFF has always been designed on the principle that the writer can write anything he damn pleases, and perhaps the reader will be able to make sense of it. Look through the spec: surely 75% of it describes features that a run-of-the-mill reader would be unable to cope with. (Show me a reader that will do something sensible with YCbCr, associated-alpha, 32-bit-float-sample images ... to take just one example. If you say your code can handle that nicely, I'll start asking about tiles, padding, downsampling, and planar configuration.) I think the spec is being quite honest here to tell you what part of the described feature set is actually likely to be portable. If this approach to compatibility doesn't thrill you, perhaps you should consider another file format. For instance, PNG, which was designed in large part on the principle that TIFF blew this issue badly. The PNG spec expects that every reader should be able to do something sensible with every PNG file, which is certainly not the design assumption of TIFF. On the other hand, you can't stick a YCbCr, associated-alpha, 32-bit-float-sample image into a PNG. You pays your money and you takes your choice... regards, tom lane organizer, Independent JPEG Group member, PNG development group onetime member, TIFF advisory committee

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2002.03.23 05:38 "Re: Changing Orientation Tag", by Tom Lane