[PDF] Entries in number tree not specified as indirect references

[Vincent Hennebert <vh...@gmail.com>]

Hi,

The StructTreeRoot dictionary must have a ParentTree entry whose type is
a number tree. As explained in Section 3.8.5, “Number Trees” of the PDF
Reference, Third Edition, the Nums entry of a number tree node must be
an array of key-value pairs where value is an indirect reference to the
object associated with the key.

This is not what is done in the current implementation of Logical
Structure in FOP (Temp_Accessibility branch). The value (an array) is
directly stored in the array of key-value pairs instead of being
referenced. So technically the PDF produced is invalid. Acrobat doesn’t
seem to complain, though.

Did I miss anything?
Thanks,
Vincent

Re: [PDF] Entries in number tree not specified as indirect references

[Jeremias Maerki <de...@jeremias-maerki.ch>]

Hi Vincent,

good catch! Your observation is correct. That value must not be a direct
object.

I guess the reason Acrobat doesn't complain is that a PDF parser usually
doesn't really care whether a PDF object is direct or indirect as it is
handled transparently. Still, another implementation might rely on the
value being an indirect object.

On 29.09.2009 16:38:05 Vincent Hennebert wrote:
> Hi,
> 
> The StructTreeRoot dictionary must have a ParentTree entry whose type is
> a number tree. As explained in Section 3.8.5, “Number Trees” of the PDF
> Reference, Third Edition, the Nums entry of a number tree node must be
> an array of key-value pairs where value is an indirect reference to the
> object associated with the key.
> 
> This is not what is done in the current implementation of Logical
> Structure in FOP (Temp_Accessibility branch). The value (an array) is
> directly stored in the array of key-value pairs instead of being
> referenced. So technically the PDF produced is invalid. Acrobat doesn’t
> seem to complain, though.
> 
> Did I miss anything?
> Thanks,
> Vincent




Jeremias Maerki