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March 2004
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2004.03.03 12:02 "Re: Hello world", by Rob Tillaart
Gerben Vos wrote: > > xevit wrote: > > > My problem is that when I'm working on a big TIFF file ( tile > > based ) I want to read and write simultaneous to the same file, > > to change small portions of my bigImage. > > I have never tried it, but I guess it should be possible to open the TIFF > as a normal file (using open() on Unix or CreateFile() on Win32; see the > code in tif_unix.c, tif_win32.c, or the appropriate file for your OS), and > then pass the returned file descriptor to TIFFFdOpen(). Then you can use > libtiff to read the strip offsets and sizes, and use the normal file > handle to lseek() (or SetFilePointer() or whatever) to the correct offset > within the file and overwrite the data there. I'm not sure whether it > would be wise to use any of libtiff's write functions. > > Of course, this will all only work when the TIFF is uncompressed! > Otherwise, the (compressed) size of the data could change, and all bets > are off. > I guess it is also possible if you only want to change the metadata/tags too, but only if you cope with them as if they are all fixed size (many of the tags are fixed size, but not all). regards, rob tillaart