xpdf
====
and pdftops

version 0.6 (beta)
96-nov-12

The xpdf and pdftops software and documentation are
copyright 1996 Derek B. Noonburg.

Email: derekn@ece.cmu.edu
WWW: http://www.contrib.andrew.cmu.edu/usr/dn0o/xpdf/xpdf.html

The PDF data structures, operators, and specification
are copyright 1995 Adobe Systems Inc.


What is xpdf?
-------------

Xpdf is a viewer for Portable Document Format (PDF) files.  (These are
also sometimes also called 'Acrobat' files, from the name of Adobe's
PDF software.)  Xpdf runs under UNIX or VMS and the X Window System.

Xpdf is designed to be small and efficient.  It does not use the Motif
or Xt libraries.  It uses standard X fonts.  Xpdf is quite usable on a
486-66 PC running Linux.


Compatibility
-------------

Xpdf is known to work on the following systems:

* x86, Linux 2.0 ELF, gcc 2.7.2
* PowerPC, AIX 4.1, gcc 2.7.0
* SPARC, Solaris 2.5, gcc 2.7.2
* Alpha, OSF/1 3.2, gcc 2.7.2
* HP-PA, HP-UX 9.05, gcc 2.7.2

It should work on pretty much any UNIX or VMS system which runs X11.
You'll need ANSI C++ and C compilers to compile it.  If you compile it
for a system not listed on the xpdf web page, please let me know.  If
you're willing to make your binary available by ftp or on the web,
I'll add a pointer to the web page.  If you can't get it to compile on
your system, I'll try to help.


Getting xpdf
------------

The latest version is available from:

  http://www.contrib.andrew.cmu.edu/usr/dn0o/xpdf/xpdf.html

or:

  ftp://ftp.andrew.cmu.edu/pub/xpdf/

Source code and several precompiled executables are available.

Announcements of new versions are posted to several newsgroups
(comp.text.pdf, comp.os.linux.announce, and others) and emailed to a
list of people.  If you'd like to receive email notification of new
versions, just let me know.


Running xpdf
------------

To run xpdf, simply type:

  xpdf file.pdf

To generate a PostScript file, hit the "print" button in xpdf, or run
pdftops:

  pdftops file.pdf

Command line options and many other details are described in the man
pages (xpdf.1 and pdftops.1) and the VMS help files (xpdf.hlp and
pdftops.hlp).


Fonts
-----

Xpdf uses X server fonts.  It requires the following fonts:

* Courier: medium-r, bold-r, medium-o, and bold-o
* Helvetica: medium-r, bold-r, medium-o, and bold-o
* Times: medium-r, bold-r, medium-i, and bold-i
* Symbol: medium-r
* Zapf Dingbats: medium-r

Most X installations should already have all of these fonts, except
Zapf Dingbats.  You can install a Type 1 Zapf Dingbats font -- see the
mkfontdir(1) man page for details.  Use this font descriptor in your
fonts.scale file:

    -itc-zapfdingbats-medium-r-normal--0-0-0-0-p-0-adobe-fontspecific

You can get a Type 1 font file from the ghostscript 4.x distribution
(look for d050000l.pfb).

X servers, starting at R5, support font scaling.  Xpdf will
automatically take advantage of this.  There are two types of scaling.
The first type uses standard bitmap fonts: if a font doesn't exist in
the requested size, the server will scale the bitmapped characters.
This is reasonably fast, and the results are readable but not very
pretty.  X servers can also handle true scalable, e.g., Type-1, fonts.
(See the mkfontdir(1) man page for details on setting these up.)
Scalable fonts are slower, especially since PDF documents tend to use
lots of fonts, but they look much nicer.

Some X servers also support font rotation.  Xpdf will use this feature
if available.


The Unisys LZW Patent
---------------------

Nearly all PDF files include data which has been compressed with the
LZW compression algorithm.  Unfortunately, LZW is covered by a
software patent which is owned by Unisys Corporation.  Unisys refuses
to license this patent for PDF-related use in software such as xpdf
which is released for free and which may be freely redistributed.
(This is same algorithm which is used by GIF.  However, Unisys is not
doing licensing for free PDF viwers in the same way as for free GIF
viewers.)

As a workaround, xpdf converts PDF-format LZW data to compress-format
LZW data.  (The standard UNIX compress utility also uses LZW, but with
a slightly different file format.)  This conversion does *not*
decompress the data; it simply converts it to a different file format.
Xpdf then calls uncompress to actually decompress the data.

I have been told by several notable people that the LZW patent covers
compression only, and does not cover decompression.  This seems pretty
fuzzy to me, so I'm going to stick with my workaround, at least for
now.

Software patents in general are a bad idea.  Consider supporting the
League for Programming Freedom <http://www.lpf.org/>.

For Unisys's slant on things (mostly regarding GIF), see
<http://www.unisys.com/LeadStory/lzwterms.html> and
<http://www.unisys.com/LeadStory/lzwfaq.html>.  These pages mention
an email address for feedback.


Compiling xpdf
--------------

Xpdf is written in C++ (with a little bit of C).  It should work with
any ANSI-compliant C++ and C compilers.  The systems and compilers
it's been tested with are listed on the xpdf web page.

To compile xpdf for UNIX:

* Edit Makefile.config in the top-level directory.  Set the compilers
  you want to use (e.g., gcc and g++) and add any necessary switches
  and options (e.g., include and library directories).  You can also
  set the installation directory here (the PREFIX variable).

* If neither 'uncompress -c file.Z' nor 'gzip -d -c file.Z' decompress
  a standard UNIX .Z file to stdout on your system, you'll need to
  change uncompressCmd in xpdf/config.h.  This should not be necessary
  on most systems.

* Type 'make' in the top-level directory to compile both xpdf and
  pdftops.  If you only want to make one of the executables, type
  'make xpdf' or 'make pdftops'.

* If nothing goes wrong, the executables will be left in xpdf/xpdf and
  xpdf/pdftops.  There are no runtime configuration or support files;
  the binary can be moved to any directory.

* If desired, type 'make install' to install the binaries and man
  pages.

To compile xpdf for VMS:

* There are two sets of scripts: vmscomp.com (for gcc on VAX) and
  vmsdecccomp.com (for DEC C on Alpha).  There are four of each: in
  the top-level directory, [.goo], [.ltk], and [.xpdf].  You may need
  to edit these scripts as appropriate for your system.

* The 'stddef.h' include file which comes with older versions of gcc
  may be missing a definition for wchar_t.  In this case, add the
  following lines:
  -----
  File GNU_CC:[INCLUDE]STDDEF.H;2
   44   /* Wide characters, not yet supported by VAXCRTL [match VAXC's <stddef.
   45   #if !defined(_WCHAR_T) && !defined(_WCHAR_T_)
   46   typedef unsigned int wchar_t;
   47   #endif
   48   #define _WCHAR_T
   49   #define _WCHAR_T_
   50
  -----

* Type '@vmscomp' or '@vmsdecccomp' in the top-level directory.

* The executables will be left in '[.xpdf]xpdf' and '[.xpdf]pdftops'.


Distribution
------------

Xpdf may be distributed under the following conditions:

1. This file ('README') is included, unmodified, in the distribution.

2. The distribution includes:
   a. all of the xpdf source code and documentation, unmodified; OR
   b. one or more xpdf executables, compiled from the unmodified
      source code, plus the associated documentation (UNIX man pages
      or VMS help files); OR
   c. both of the above.

If you distribute xpdf, I would appreciate receiving a pointer (ftp
site, BBS phone number, etc.) or a copy (disk, CD-ROM, etc.).

Modified versions of xpdf or applications using some or all of the
xpdf code (i.e., 'derivative works' under copyright law) may not be
distributed without explicit permission.


Bugs
----

This is an beta release of xpdf, and there are still a bunch of PDF
features which I have yet to implement.

At this point, the biggest problem is that embedded fonts are not
handled correctly.

If you find a bug in xpdf, i.e., if it prints an error message,
crashes, or incorrectly displays a document, and you don't see that
bug listed here, please send me email, with a pointer (URL, ftp site,
etc.) to the PDF file.


Acknowledgments
---------------

Thanks to:

* Patrick Voigt for help with the remote server code.
* Patrick Moreau for the VMS port.
* David Boldt and Rick Rodgers for sample man pages.


References
----------

Adobe Systems Inc., _Portable Document Format Reference Manual_.
Addison-Wesley, 1993, ISBN 0-201-62628-4.
[The manual for PDF version 1.0.  The updated version (for PDF 1.1) is
available on the net from http://www.adobe.com/Support/TechNotes.html
or ftp://ftp.adobe.com/pub/adobe/Acrobat/SDK/TECHDOC/PDFSPEC.PDF.]

Adobe Systems Inc., _Updates to the Portable Document Format Reference
Manual_, Adobe Developer Support Technical Note #5156.  1995.
[Updates for PDF version 1.1.  Available on the WWW as
http://www.adobe.com/PDFs/TN/5156.PDF_UPD.PDF.]

Adobe Systems Inc., _Updates to the Portable Document Format Reference
Manual_.
[Update for Sections 5.7 and 6.12 (encryption), emailed to developers
July 24, 1996.]

Adobe Systems Inc., _PostScript Language Reference Manual_, 2nd ed.
Addison-Wesley, 1990, ISBN 0-201-18127-4.
[The official PostScript manual.]

Adobe Systems Inc., _Supporting the DCT Filters in PostScript Level
2_, Adobe Developer Support Technical Note #5116.  1992.
[Description of the DCTDecode filter parameters.]

Anonymous, RC4 source code.
[This is the algorithm used to encrypt PDF files.  Available on
various ftp sites, e.g., ftp://ftp.ox.ac.uk/pub/crypto/misc/rc4.tar.gz
or ftp://idea.sec.dsi.unimi.it/pub/crypt/code/rc4.tar.gz.]

CCITT, _Blue Book_, Volume VII Fascicle 3: "Terminal Equipment and
Protocols for Telematic Services", Recommendations T.4 and T.6.
[The official Group 3 and 4 fax standards.  These are available on the
net (but misformatted) as
ftp://ftp.uu.net/doc/standards/ccitt/1988/7_3_01.ps and 7_3_02.ps.]

Foley, van Dam, Feiner, and Hughes, _Computer Graphics: Principles and
Practice_, 2nd ed.  Addison-Wesley, 1990, ISBN 0-201-12110-7.
[Colorspace conversion functions, Bezier spline math.]

Robert L. Hummel, _Programmer's Technical Reference: Data and Fax
Communications_.  Ziff-Davis Press, 1993, ISBN 1-56276-077-7.
[CCITT Group 3 and 4 fax decoding.]

Christoph Loeffler, Adriaan Ligtenberg, George S. Moschytz, "Practical
Fast 1-D DCT Algorithms with 11 Multiplications".  IEEE Intl. Conf. on
Acoustics, Speech & Signal Processing, 1989, 988-991.
[The fast IDCT algorithm used in the DCTDecode filter.]

R. Rivest, "The MD5 Message-Digest Algorithm".  RFC 1321.
[MD5 is used in PDF document encryption.]

Gregory K. Wallace, "The JPEG Still Picture Compression Standard".
[Good description of the JPEG standard.  Available on the net as
ftp://ftp.uu.net/graphics/jpeg/wallace.ps.gz.  Also published in CACM,
April 1991, and submitted to IEEE Transactions on Consumer
Electronics.]
