Why not extract the page content and hash that?
From: Yuvi Masory [mailto:[email protected]]
Sent: Wednesday, September 29, 2010 12:05 PM
To: iText Questions
Subject: Re: [iText-questions] how to get zero diff on two consecutively
created pdf files
Well I hope you like tea because they're already out:
http://yuvimasory.com/flashcards.html
I want iText to behave this way because I have a script that rebuilds all my
pdfs every night to benefit from the latest changes in my program. However, I
*don't* want meaningless revisions to complicate my source tree in Git. So
ideally, if the program has not changed, the pdfs that result will be
identicai, and Git will not commit them.
Anyway, does anyone have suggestions as to how to construct a reproducible
unique ID for a file? Perhaps traversing the Document in some way as to make a
string from its contents?
Thanks again for the help.
Best,
Yuvi
--
Yuvi Masory
University of Pennsylvania
On Wed, Sep 29, 2010 at 7:45 AM, Leonard Rosenthol
<[email protected]<mailto:[email protected]>> wrote:
Can you tell us what you are doing that you need iText to work this way?
Because if you're files show up in the real world with the matching IDs, I will
get on the R3 downtown to the U of P for a "personal visit"....
Leonard
From: Yuvi Masory [mailto:[email protected]<mailto:[email protected]>]
Sent: Wednesday, September 29, 2010 7:38 AM
To: iText Questions
Subject: Re: [iText-questions] how to get zero diff on two consecutively
created pdf files
Thanks for the feedback everyone! Right now the patch meets my needs, but I may
modify it to construct unique (reproducible) IDs when I have the chance.
Best,
Yuvi
--
Yuvi Masory
University of Pennsylvania
On Wed, Sep 29, 2010 at 7:01 AM, Leonard Rosenthol
<[email protected]<mailto:[email protected]>> wrote:
As Michael said, the ID is indeed that - a UNIQUE identifier for the document
and is indeed used in that way by various CMS/DMS systems to track the document.
So if your code is being used in DEBUG mode for some sort of regression test -
that's fine. But you can NOT put it into a production system.
Leonard
-----Original Message-----
From: mkl [mailto:[email protected]<mailto:[email protected]>]
Sent: Wednesday, September 29, 2010 6:36 AM
To:
[email protected]<mailto:[email protected]>
Subject: Re: [iText-questions] how to get zero diff on two consecutively
created pdf files
Yuvi,
Yuvi Masory wrote:
> 3) The PDF's trailer includes a randomly generated String as its file ID -
> solved by changing the appropriate method in PdfEncryption to always hash
> the empty string.
That could turn out against you eventually: As the trailer IDs are meant to
be identifiers for documents and your patched code calculates the identical
one for ANY document, other applications may consider all the documents you
generate with that patched iText to be identical. This might result in them
rejecting or silently discarding your documents as duplicates.
Therefore, I would advice you to reconsider this part of your patch: Either
generate an ID which is unique for the generated document but reproducible,
or change the patch to not include a trailer ID at all.
Regards, Michael.
--
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