Re: [PATCH] Disable PDF docinfo output for EPS

[<lud...@la...>]

Hi,

Ethan Merritt <merritt@u.washington.edu> writes:

> On Friday 05 October 2007 02:36, Ludovic Courtès wrote:
>> Hi,
>> 
>> Just in case you missed it, I recently posted a tiny patch to disable
>> PDF docinfo output for EPS:
>> 
>>   http://article.gmane.org/gmane.comp.graphics.gnuplot.bugs/1316
>
> I consider the current gnuplot behaviour to be correct.
> The pdfmark constuct allows passing metadata through to PDF, and
> Adobe's PDF Reference, Third Edition states (Section 9):

The problem is not with PDF, but rather with the interpretation of the
`pdfmark' operator by "distiller" applications such as ps2pdf: the
"pdfmark Reference Manual" [0] does not specify how multiple instances
of an "Info dictionary pdfmark" should be handled.

Consider the following PostScript file:

  %!PS-Adobe-3.0
  %%DocumentMedia: A4 595 842 0 white ()
  %%PageOrder: Ascend
  %%LanguageLevel: 2
  %%BoundingBox: 0 0 595 842

  [ /Title (First Title)
     /Author (First Author)
     /Subject (First Subject)
     /DOCINFO
  pdfmark

  [ /Title (Second Title)
     /Author (Second Author)
     /Subject (Second Subject)
     /DOCINFO
  pdfmark

With GhostScript's ps2pdf and `pdfinfo' from Xpdf, I get this:

  $ ps2pdf ,,t.ps
  $ pdfinfo ,,t.pdf
  Title:          Second Title
  Subject:        Second Subject
  Author:         Second Author
  Producer:       GPL Ghostscript 8.56
  CreationDate:   Tue Oct  9 07:54:12 2007
  ModDate:        Tue Oct  9 07:54:12 2007
  Tagged:         no
  Pages:          1
  Encrypted:      no
  Page size:      595 x 842 pts (A4)
  File size:      2275 bytes
  Optimized:      no
  PDF version:    1.4

Which means that the second Info dictionary overrode the first.  Same
result with Acrobat Distiller:

  $ pdfinfo ,,t.acrobat-distiller-7.pdf 
  Title:          Second Title
  Subject:        Second Subject
  Author:         Second Author
  Producer:       Acrobat Distiller 7.0.5 pour Macintosh
  CreationDate:   Tue Oct  9 09:56:34 2007
  ModDate:        Tue Oct  9 09:56:34 2007
  Tagged:         no
  Pages:          1
  Encrypted:      no
  Page size:      612 x 792 pts (letter)
  File size:      5057 bytes
  Optimized:      yes
  PDF version:    1.4

Indeed, both PDF files only contain the second Info dictionary.

Including a GNUplot-generated EPS file in a PS file that already
contains its own Info dictionary marker is likely to lead to the same
situation, unless the PS file is arranged such that its Info dictionary
marker appears  after  the embedded EPS file.

It turns out that both LaTeX+hyperref and Lout (which is what I use) put
their Info dictionary marker at the beginning of the PS document; thus,
that Info dictionary gets overridden by the one present in the
included GNUplot-generated EPS files.  QED.


Furthermore, I question the usefulness of `pdfmark' in EPS files.  EPS
files are meant to be embedded, as the name implies, and probably not
converted to PDF.  Thus, `pdfmark' instances within EPS appear to be of
little use; `pdfmark' in *PS* files, OTOH, are admittedly useful, and my
patch preserves them.

Thanks,
Ludovic.

[0] http://partners.adobe.com/public/developer/en/acrobat/sdk/pdf/pdf_creation_apis_and_specs/pdfmarkReference.pdf