2004.05.18 17:47 "[Tiff] Recovering tiff faxes corrupted with 3.6.0", by Andrew McGill

2004.05.19 13:54 "[Tiff] Re: Recovering tiff faxes corrupted with 3.6.0", by Frank Warmerdam

Thanks for the reply - I stayed up late in this time zone, and yes, I did find that hacking tiffset was not the joy I had intended. I did download a copy of the TIFF spec (6.0) from Adobe, and I found that the following fixes this corruption very neatly (and corrupts perfectly good tiff files as well):

#! /usr/bin/perl
# Public domain
# 266       03=short                      01=std, 02=rev
# Tag       Type      Count               Value
# 0    1    2    3    4    5    6    7    8
use English;
undef $IFS;
while(<>) {

The code searches for the "FillOrder" block tag = 0A01 type=0300 count=01000000 value=0200 and sets the value to 0100, which reverses the bit order. (I couldn't convince perl to search for \x0A which should be at the head of the block, so I left it off).

The reason this works, as I understand it is that libtiff (unpatched) reversed the fillorder in the data, but the header was marked as read-only. Reversing the fillorder in the header makes the files readable again.


I have taken the liberty of cc:ing this to the mailing list in case it is helpful to anyone else, or if anyone recognises this as some sort of bug in libtiff. The list archive is my (and the communities) memory. :-)

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@pobox.com
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