Corrupt pdf files, any advice.
Julian Field
mailscanner at ecs.soton.ac.uk
Tue Jul 29 12:22:55 IST 2003
Dean has kindly sent me the qf+df files from a message containing a PDF
file that is corrupted. He has also sent me the original untouched PDF file
to compare with the df file.
Well, whatever generated the original quoted-printable message
X-Mailer: Internet Mail Service (5.5.2653.19)
did it wrong.
If you do an "od -c" on the test1.pdf file you get this:
0000000 % P D F - 1 . 2 \r % â ã Ï Ó \r \n
0000020 6 3 2 6 0 o b j \r < < \r /
Note the \r\n at the end of the first line, just before the 6326.
but if you do an "od -c" of the quoted-printable message contents (so you
can see any embedded newline characters and so on), you get this:
0000000 % P D F - 1 . 2 = 0 D % = E 2 =
0000020 E 3 = C F = D 3 \n 6 3 2 6 0
0000040 o b j = 0 D < < = 0 D /
Now look what has happened to the data just before the 6326. It has been
squashed into 1 \n character, thereby destroying the \r in the original.
I can only imagine that Outlook/Exchange saw the \r\n sequence near the
start of the file, and concluded that it was a text-based file. It
therefore saw nothing wrong in squashing \r\n into just \n, which would
work fine on a text file. Unfortunately its original decision about the
file was wrong in this case :-(
This makes it
a) Microsoft's fault
and
b) Not a problem I can work around, as their software has destroyed data
that I cannot reconstruct.
Outlook XP always appears to use Base64, so I suspect the problem may just
exist in Exchange 5.5 and/or Outlook 97. Don't know about Outlook 2000.
Whether Acrobat Reader (on some platforms) will continue to be able to use
the damaged file is another matter entirely, something over which I have no
control.
All I can suggest is you request people using the particular troublesome
versions always zip their PDF files to stop Outlook destroying them.
If anyone has any ideas about a software workaround I could implement,
please let me know as I can't think of any way of doing it right now.
--
Julian Field
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