On 2015-09-17 08:57, Leonard Rosenthol wrote:
While it is unclear in ISO 32000-1 whether such a PDF is invalid, we
made it clear in 32000-2 that you can only have one copy of each page
in the Pages tree. So personally, I wouldn’t waste much time on this
particular file.
Leonard
OK, if it's not allowed by the spec, I have no real objection to the
object count check.
On 9/17/15, 1:04 AM, "poppler on behalf of Jason Crain"
<poppler-boun...@lists.freedesktop.org on behalf of
ja...@aquaticape.us> wrote:
On Wed, Sep 16, 2015 at 09:05:58PM -0400, William Bader wrote:
> > I don't know of a good way to validate the page count. Even
> > going through the page tree might be hard to do right without
> > leading to an infinite loop, in addition to being slow.
>
> Catalog::cachePageTree goes over the tree, but i agree doing that
> to calculate the num of pages can be meh.
If the number of pages is huge, the PDF might be intentionally
corrupted to provoke a bug in a particular PDF viewer, and other
data structures could be subtly corrupted as well. Any scan would
have to proceed very cautiously.
If there is a minimum number of objects required for a page, and if
the total number of objects is easy to find, could poppler
immediately reject files with (total num objects) / (min objects per
page) < page count?
The document at
https://drive.google.com/open?id=0ByTyiZeyQ4p9cTVBUllNRmI3bmM is what
I'm thinking of. It has 5 objects and a single page that is listed in
the /Kids array 10 times. Duplicating the page just means adding it
to the array again and incrementing /Count. If we want this document
to work then there's really no minimum number of objects required for
a page. Otherwise, each page would require at least a /Page object.
FWIW Adobe Reader shows an error on the document after the first
duplicated page. Other viewers show it just fine.
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