After some brief research, trial and error, and review of the source code, tiffset did the track. Interesting that the help and man page for tiffset indicate that a tag name is required, while in actual fact it seems that a decimal tag number is used.
----- Original Message -----
From: Kevin Myers
To: tiff@... ; graphicsmagick-help@...
Sent: Wednesday, March 04, 2009 13:17
Subject: Alter TIFF Orientation
I received a number of extremely large TIFF images where the orientation value in the TIFF header has been incorrectly set to BOTTOM in the header rather than TOP, and that is causing the images to be displayed upside-down. In theory I might be able to rotate these images 180 degrees using something like GraphicsMagick without changing the orientation value, but that would be extremely slow. All that I really need to do is change the orientation value in the header from BOTTOM to TOP. Are there any utilities that allow this simple change to be performed?