AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

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

2002.03.22 21:13 "Re: Changing Orientation Tag", by Peter Smith

** Reply to message from "Erika Nesse" <enesse@umich.edu> on Wed, 20 Mar 2002 11:37:49 -0500

I was wondering if anyone knows of any software that changes the orientation of tiffs by toggling the orientation tag, instead of actually changing the order of the data?

That's what I do in my cheque-processing software. If a document is imaged upside-down and the operator clicks the "invert" button, I just change the orientation tag and leave the image unchanged. Any viewer worth using should interpret the orientation tag if it is present. If it doesn't, you have a crappy viewer.

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."

I have been tempted to use this tag myself, but this wording has scared me away. In the case that you describe, Jon, I think the spec makes it pretty clear that you should "invert" the image in your software and not leave it up to the viewer.

It makes me wonder why this tag was even included in the spec.

Peter