okular/README.xpdf

Xpdf
====

version 1.01
2002-may-20

The Xpdf software and documentation are
copyright 1996-2002 Glyph & Cog, LLC.

Email: derekn@foolabs.com
WWW: http://www.foolabs.com/xpdf/

The PDF data structures, operators, and specification are
copyright 1985-2001 Adobe Systems Inc.


What is Xpdf?
-------------

Xpdf is an open source viewer for Portable Document Format (PDF)
files.  (These are also sometimes also called 'Acrobat' files, from
the name of Adobe's PDF software.)  The Xpdf project also includes a
PDF text extractor, PDF-to-PostScript converter, and various other
utilities.

Xpdf runs under the X Window System on UNIX, VMS, and OS/2.  The non-X
components (pdftops, pdftotext, etc.) also run on Win32 systems and
should run on pretty much any system with a decent C++ compiler.

Xpdf is designed to be small and efficient.  It can use Type 1,
TrueType, or standard X fonts.


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

Xpdf is licensed under the GNU General Public License (GPL), version
2.  In my opinion, the GPL is a convoluted, confusing, ambiguous mess.
But it's also pervasive, and I'm sick of arguing.  And even if it is
confusing, the basic idea is good.

In order to cut down on the confusion a little bit, here are some
informal clarifications:

- I don't mind if you redistribute Xpdf in source and/or binary form,
  as long as you include all of the documentation: README, man pages
  (or help files), and COPYING.  (Note that the README file contains a
  pointer to a web page with the source code.)

- Selling a CD-ROM that contains Xpdf is fine with me, as long as it
  includes the documentation.  I wouldn't mind receiving a sample
  copy, but it's not necessary.

- If you make useful changes to Xpdf, please make the source code
  available -- post it on a web site, email it to me, whatever.

If you're interested in commercial licensing, please see the Glyph &
Cog web site:

    http://www.glyphandcog.com/


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

Xpdf is developed and tested on a Linux 2.2 x86 system.

In addition, it has been compiled by others on Solaris, AIX, HP-UX,
SCO UnixWare, Digital Unix, Irix, and numerous other Unix
implementations, as well as VMS and OS/2.  It should work on pretty
much any system which runs X11 and has Unix-like libraries.  You'll
need ANSI C++ and C compilers to compile it.

The non-X components of Xpdf (pdftops, pdftotext, pdfinfo, pdffonts,
pdfimages) can also be compiled on Win32 systems.  See the Xpdf web
page for details.

If you compile Xpdf for a system not listed on the web page, please
let me know.  If you're willing to make your binary available by ftp
or on the web, I'll be happy to add a link from the Xpdf web page.  I
have decided not to host any binaries I didn't compile myself (for
disk space and support reasons).

If you can't get Xpdf to compile on your system, send me email and
I'll try to help.

Xpdf has been ported to the Acorn, Amiga, BeOS, and EPOC.  See the
Xpdf web page for links.


Getting Xpdf
------------

The latest version is available from:

  http://www.foolabs.com/xpdf/

or:

  ftp://ftp.foolabs.com/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

To generate a plain text file, run pdftotext:

  pdftotext file.pdf

There are four additional utilities (which are fully described in
their man pages):

  pdfinfo -- dumps a PDF file's Info dictionary (plus some other
             useful information)
  pdffonts -- lists the fonts used in a PDF file along with various
              information for each font
  pdftopbm -- converts a PDF file to a series of PBM-format bitmaps
  pdfimages -- extracts the images from a PDF file

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


Upgrading from Xpdf 0.9x
------------------------

WARNING: Xpdf 1.x uses a completely different config file setup than
Xpdf 0.9x.

Many of the configuration options that used to be X resources have
been moved into the Xpdf config file.  There are also lots of new and
improved options.  If you're upgrading from Xpdf 0.9x, please read
through the sample config file (doc/sample-xpdfrc) and the xpdfrc(5)
man page.

The Asian language support has been pulled out into separate packages,
loaded at run time.  This is much cleaner than the 0.9x approach -- it
makes the base distribution smaller, allows the language support
packages to be upgraded separately, and lets users customize Xpdf for
other text encodings without modifying the source.  See the web site
(http://www.foolabs.com/xpdf) for info on downloading the language
support packages.

All of the Xpdf tools, including the X viewer and the command line
programs, read the same config file.  They first attempt to read the
user's personal config file:

    $HOME/.xpdfrc

If it is not found, the Xpdf tools read a system-wide config file,
typically something like:

    /usr/local/etc/xpdfrc

(this location can be customized when building Xpdf).

The Win32 command line tools look in the directory containing the
executable, e.g.:

    C:/Program Files/Xpdf/xpdfrc

Xpdf 1.x comes with a "sample-xpdfrc" file in the doc directory.  This
is a good starting point for constructing your own config file.

For full details, please see the xpdfrc(5) man page.


Fonts
-----

By default, Xpdf will use 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
maybe Zapf Dingbats).

If Xpdf is built with support for t1lib (or FreeType 2), you can get
much higher quality text by using Type 1 fonts instead of X server
fonts.  For example, you can use the Type 1 fonts that come with
ghostscript.  To do this, add the following lines to the xpdfrc file
(e.g., /usr/local/etc/xpdfrc or $HOME/.xpdfrc):

displayFontT1 Times-Roman		/usr/local/share/ghostscript/fonts/n021003l.pfb
displayFontT1 Times-Italic		/usr/local/share/ghostscript/fonts/n021023l.pfb
displayFontT1 Times-Bold		/usr/local/share/ghostscript/fonts/n021004l.pfb
displayFontT1 Times-BoldItalic		/usr/local/share/ghostscript/fonts/n021024l.pfb
displayFontT1 Helvetica			/usr/local/share/ghostscript/fonts/n019003l.pfb
displayFontT1 Helvetica-Oblique		/usr/local/share/ghostscript/fonts/n019023l.pfb
displayFontT1 Helvetica-Bold		/usr/local/share/ghostscript/fonts/n019004l.pfb
displayFontT1 Helvetica-BoldOblique	/usr/local/share/ghostscript/fonts/n019024l.pfb
displayFontT1 Courier			/usr/local/share/ghostscript/fonts/n022003l.pfb
displayFontT1 Courier-Oblique		/usr/local/share/ghostscript/fonts/n022023l.pfb
displayFontT1 Courier-Bold		/usr/local/share/ghostscript/fonts/n022004l.pfb
displayFontT1 Courier-BoldOblique	/usr/local/share/ghostscript/fonts/n022024l.pfb
displayFontT1 Symbol			/usr/local/share/ghostscript/fonts/s050000l.pfb
displayFontT1 ZapfDingbats		/usr/local/share/ghostscript/fonts/d050000l.pfb

You will need to replace '/usr/local/share/ghostscript/fonts' with the
appropriate path on your system.


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 viewers 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.

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
--------------

See the separate file, INSTALL.


Bugs
----

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, Martin P.J. Zinser, and David Mathog for the VMS
  port.
* David Boldt and Rick Rodgers for sample man pages.
* Brendan Miller for the icon idea.
* Olly Betts for help testing pdftotext.
* Peter Ganten for the OS/2 port.
* Michael Richmond for the Win32 port of pdftops and pdftotext.
* Frank M. Siegert for improvements in the PostScript code.
* Leo Smiers for the decryption patches.
* Rainer Menzner for creating t1lib, and for helping me adapt it to
  xpdf.
* Pine Tree Systems A/S for funding the OPI and EPS support in
  pdftops.
* Easy Software Products for funding the "sh" operator support.
* Tom Kacvinsky for help with FreeType and for being my interface to
  the FreeType team.
* Theppitak Karoonboonyanan for help with Thai support.
* Leonard Rosenthol for help and contributions on a bunch of things.
* Alexandros Diamantidis and Maria Adaloglou for help with Greek
  support.
* Lawrence Lai for help with the CJK Unicode maps.

Various people have contributed modifications made for use by the
pdftex project:

* Han The Thanh
* Martin Schr<68>der of ArtCom GmbH


References
----------

Adobe Systems Inc., _PDF Reference: Adobe Portable Document Format
version 1.4_, 3nd ed.
Addison-Wesley, 2001, ISBN 0-201-75839-3.
http://partners.adobe.com/asn/developer/acrosdk/docs/filefmtspecs/PDFReference.pdf
[The printed manual for PDF version 1.4.]

Adobe Systems Inc., _Portable Document Format: Changes from Version
1.3 to 1.4_, Adobe Developer Support Technical Note #5409.
June 11, 2001.
http://partners.adobe.com/asn/developer/acrosdk/docs/filefmtspecs/PDF14Deltas.pdf
[Updates for PDF 1.4.]

Adobe Systems Inc., _PostScript Language Reference_, 3rd ed.
Addison-Wesley, 1999, ISBN 0-201-37922-8.
[The official PostScript manual.]

Adobe Systems, Inc., _The Type 42 Font Format Specification_,
Adobe Developer Support Technical Specification #5012.  1998.
http://partners.adobe.com/asn/developer/pdfs/tn/5012.Type42_Spec.pdf
[Type 42 is the format used to embed TrueType fonts in PostScript
files.]

Adobe Systems, Inc., _Adobe CMap and CIDFont Files Specification_,
Adobe Developer Support Technical Specification #5014.  1995.
http://www.adobe.com/supportservice/devrelations/PDFS/TN/5014.CIDFont_Spec.pdf
[CMap file format needed for Japanese and Chinese font support.]

Adobe Systems, Inc., _Adobe-Japan1-4 Character Collection for
CID-Keyed Fonts_, Adobe Developer Support Technical Note #5078.
2000.
http://partners.adobe.com/asn/developer/PDFS/TN/5078.CID_Glyph.pdf
[The Adobe Japanese character set.]

Adobe Systems, Inc., _Adobe-GB1-3 Character Collection for
CID-Keyed Fonts_, Adobe Developer Support Technical Note #5079.
1998.
http://partners.adobe.com/asn/developer/PDFS/TN/5079.GB_CharColl.pdf
[The Adobe Chinese GB (simplified) character set.]

Adobe Systems, Inc., _Adobe-CNS1-3 Character Collection for
CID-Keyed Fonts_, Adobe Developer Support Technical Note #5080.
2000.
http://partners.adobe.com/asn/developer/PDFS/TN/5080.CNS_CharColl.pdf
[The Adobe Chinese CNS (traditional) character set.]

Adobe Systems Inc., _Supporting the DCT Filters in PostScript Level
2_, Adobe Developer Support Technical Note #5116.  1992.
http://www.adobe.com/supportservice/devrelations/PDFS/TN/5116.PS2_DCT.PDF
[Description of the DCTDecode filter parameters.]

Adobe Systems Inc., _Open Prepress Interface (OPI) Specification -
Version 2.0_, Adobe Developer Support Technical Note #5660.  2000.
http://partners.adobe.com/asn/developer/PDFS/TN/5660.OPI_2.0.pdf

Adobe Systems Inc., CMap files.
ftp://ftp.oreilly.com/pub/examples/nutshell/cjkv/adobe/
[The actual CMap files for the 16-bit CJK encodings.]

Adobe Systems Inc., Unicode glyph lists.
http://partners.adobe.com/asn/developer/type/unicodegn.html
http://partners.adobe.com/asn/developer/type/glyphlist.txt
http://partners.adobe.com/asn/developer/type/corporateuse.txt
http://partners.adobe.com/asn/developer/type/zapfdingbats.txt
[Mappings between character names to Unicode.]

Aldus Corp., _OPI: Open Prepress Interface Specification 1.3_.  1993.
http://partners.adobe.com/asn/developer/PDFS/TN/OPI_13.pdf

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

T. Boutell, et al., "PNG (Portable Network Graphics) Specification,
Version 1.0.  RFC 2083.
[PDF uses the PNG filter algorithms.]

CCITT, _Blue Book_, Volume VII Fascicle 3: "Terminal Equipment and
Protocols for Telematic Services", Recommendations T.4 and T.6.
ftp://ftp.uu.net/doc/standards/ccitt/1988/7_3_01.ps
ftp://ftp.uu.net/doc/standards/ccitt/1988/7_3_02.ps
[The official Group 3 and 4 fax standards.  The online copies are
unfortunately misformatted.]

A. Chernov, "Registration of a Cyrillic Character Set".  RFC 1489.
[Documentation for the KOI8-R Cyrillic encoding.]

Roman Czyborra, "The ISO 8859 Alphabet Soup".
http://czyborra.com/charsets/iso8859.html
[Documentation on the various ISO 859 encodings.]

L. Peter Deutsch, "ZLIB Compressed Data Format Specification version
3.3".  RFC 1950.
[Information on the general format used in FlateDecode streams.]

L. Peter Deutsch, "DEFLATE Compressed Data Format Specification
version 1.3".  RFC 1951.
[The definition of the compression algorithm used in FlateDecode
streams.]

Jim Flowers, "X Logical Font Description Conventions", Version 1.5, X
Consortium Standard, X Version 11, Release 6.1.
ftp://ftp.x.org/pub/R6.1/xc/doc/hardcopy/XLFD/xlfd.PS.Z
[The official specification of X font descriptors, including font
transformation matrices.]

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.]

Microsoft, _TrueType 1.0 Font Files_, rev. 1.66.  1995.
http://www.microsoft.com/typography/tt/tt.htm
[The TrueType font spec (in MS Word format, naturally).]

Thai Industrial Standard, "Standard for Thai Character Codes for
Computers", TIS-620-2533 (1990).
http://www.nectec.or.th/it-standards/std620/std620.htm
[The TIS-620 Thai encoding.]

P. Peterlin, "ISO 8859-2 (Latin 2) Resources".
http://sizif.mf.uni-lj.si/linux/cee/iso8859-2.html
[This is a web page with all sorts of useful Latin-2 character set and
font information.]

Charles Poynton, "Color FAQ".
http://www.inforamp.net/~poynton/ColorFAQ.html
[The mapping from the CIE 1931 (XYZ) color space to RGB.]

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

Unicode Consortium, "Unicode Home Page".
http://www.unicode.org/
[Online copy of the Unicode spec.]

W3C Recommendation, "PNG (Portable Network Graphics) Specification
Version 1.0".
http://www.w3.org/Graphics/PNG/
[Defines the PNG image predictor.]

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

F. Yergeau, "UTF-8, a transformation format of ISO 10646".  RFC 2279.
[A commonly used Unicode encoding.]