Re: [pdf-devel] GNUpdf and other PDF projects

[jemarch]

Hi Sylvain.

   I'd like to start a wiki page to reference other PDF projects,
   explain which one we could reuse and which ones we won't/can't (and
   why).

   It also explains part of the "goals and motivation" of the project:
   a person on IRC was wondering why we were reimplementing from
   scratch rather than improving existing software.

I think it is a good idea. You did a quite useful research! :)

   1. Currently, the most(?) advanced free code for reading PDFs is
      libpoppler, itself based on xpdf, which is GPLv2 only (not GPL2+ /
      "or later"). This causes issues in chain, e.g. GNOME software such
      as Evince can't upgrde to GPLv3, and thus this is an incentive not
      to upgrade Gtk to LGPLv3. GNUpdf is GPLv3+.

Yes, the xpdf license is the non-technical issue with libpoppler. The
poppler developers are doing their best licensing their extensions as
GPLv2+, but it is difficult to overcome the GPLv2 only codebase that
xpdf is.  

     - mupdf (PDF library) + fitz (vector graphics engine)
       http://ccxvii.net/fitz/ - Fitz and MuPDF
       http://ccxvii.net/darcsweb.cgi?r=fitz - fitz change log
       http://ghostpdf.com/new.html - GhostPDF

       Only for implementing readers?
       What's the project activity?

       License: KO - GPLv2

From http://ccxvii.net/darcsweb.cgi?r=fitz;a=headblob;f=/README :

   "This program is free software: you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation, either version 2 of the
    License, or (at your option) any later version."

so I think they already upgraded to GPLv2+. That means that we can
reuse code from mupdf and Fitz.

Fitz is a new graphics library from the ghostscript people, and seems
very promising. I find the possibility of linking fitz with the
document layer of libgnupdf quite interesting.

     - SumatraPDF - PDF reader, Windows-only but Free Software,
       http://blog.kowalczyk.info/software/sumatrapdf/

       Uses modified mupdf: http://krzysztofkowalczyk.pbwiki.com/mupdf

       License: KO - "Sumatra PDF is distributed under GPLv2 license."
       (no proper license notices)

       PDF Compatibility: mentions 1.6

         "Sumatra has a minimalistic design. Simplicity has a higher
         priority than a lot of features."
         -> incomplete PDF support?

SumatraPDF only works on windows.

     - GNU GhostScript: -> "In December 2005, Marchesi tried to update
       the Ghostscript PDF interpreter that gv uses, only to find it was
       technically impractical."  -- http://www.linux.com/feature/122195

       Details? Limitations?

The PDF interpreter included in ghostscript is written in
postscript. That leads to a lot of non-technical difficulties, such as
to find postscript-capable hackers to maintain it.

Besides, since the PDF interpreter is embedded in ghostscript, to
extend it to support PDF generation (other than the ghostcript pdf
writer backend) and manipulation (at both document and object levels)
would be quite difficult.

The ghostscript people went ahead to write a new lightweight PDF
interpreter called GhostPDF, independent from ghostscript. It seems
(it is somewhat obscure) that Mupdf+Fitz is a proof of concept of that
effort. I don't know if mupdf+fitz is still considered as a prototype
nor the plans artifex may have for it.

       License: KO - GPLv2 (huh?)

Ralph mentioned in this list the possibility of upgrading the license
of ghostscript from GPLv2 to GPLv2+. 

Such an upgrade would really make my day/year: we want a GPLv3
postscript interpreter! :)

     - iText - Java library, PDF generation, used by pdftk,
       http://www.lowagie.com/iText/

       License: OK - dual-licensed MPL/LGPLv2+, 

iText is a quite complete library, and what is more important: it is a
general purpose one. Like gnupdf it is following the general
layer-based design of the Acrobat SDK.

Unfortunately it is written in Java.

-- 
Jose E. Marchesi  <address@hidden>
                  http://www.jemarch.net
GNU Project       http://www.gnu.org