2014.05.02 02:19 "Re: [Tiff] Inconsistencies in tiff library tool operation", by Bob Friesenhahn

I am a long-time contributer to Netpbm. I am currently working on Netpbm programs tifftopnm and pamtotiff. With tifftopnm, certain images procured from the following site keep giving me problems:

ftp://ftp.remotesensing.org/pub/libtiff/pics-3.8.0.tar.gz

To determine whether the problems were caused by Netpbm code or the Tiff library which it links to, I tried some tests. I ran tiff2rgba, tiff2ps, tiffcp and tiffcmp feeding images from the above test suite and recorded the exit codes. I also ran everything under valgrind.

I notice that the exit codes are not consistent. (See below.) For example, an input file which tiff2rgba successfully converts fails when compared against itself with tiffcmp.

Some of the libtiff utilities are not up to snuff and need the caliber of someone who has been a long-time contributor to Netpbm to bring them up to Netpbm quality.

Using GraphicsMagick and recent development libtiff I am seeing only a problem with 'text.tif' which I see produced a valgrind problem in your tests. I recall that all of these files used to work so this failure is likely due to a change in libtiff.

These might be caused by errors in the Tiff library. Another possibility is that the images are half-accurate, not truly compliant to standards, and different programs handle them in different ways. Ideally, tools should be consistent; any differences should be documented.

Most of these images are best described as technology demos. They are well beyond "baseline" TIFF.

You can find other interesting TIFF samples at "ftp://ftp.graphicsmagick.org/pub/tiff-samples/". Many of these are best described as technology demos but some are "baseline" TIFF.

Security-related patches to libtiff 4 and utilities have caused issues with reading some files.

Also, I'd like to know if there is a way to determine out whether a Tiff image file is faithful to specifications.

There is no validation test like that. We do our best and then use our eyeballs to see if the results look correct, and try other well respected software to see if it looks the same.

Bob
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Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/