2004.09.02 01:27 "Re: [Tiff] Stacked tiffs with colourmaps", by Joris
Is there any easier/ more efficient way to do this? - it would seem to make sense if only one colourmap was added that all the planes could refer to.
See also http://www.asmail.be/msg0054796490.html, because subject returned in other thread.
Once or twice every couple of years, the TIFF 7.0 subject comes up. That is a tradition of almost a decade old, and I'm quite sure it'll continue for at least as long still. On such occasions, I always add that I'd like to see memory management in TIFF 7.0, and reference counting. That would solve your problem too, you could have one color map, counted-referenced in all IFD's.
Unfortunately, TIFF 6.0 doesn't include that. There is no legal solution to your problem, I think.
*But* if you are very sure that your files will not escape into the wild, and will not get edited by TIFF page-joggling or other tools, you could nevertheless write the color map only once, and state the same color map offset in all IFD's. That is *not legal* in TIFF 6.0, but it takes some analysis to detect even, so normal readers would not have any problems with the file. Neither would transcoders. Only apps that, for instance, delete pages and try to reuse lost memory writing other data into it and such, would cause problems.
I repeat that this is *not legally TIFF 6.0*. I also have no clue how to do it with LibTiff, should you nevertheless want to.
Joris Van Damme
Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html