xpdf
====

version 0.90
99-aug-02

The xpdf software and documentation are
copyright 1996-1999 Derek B. Noonburg.

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

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 the X Window System on UNIX, VMS, and
OS/2.  The non-X components of the package (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 does not use the Motif
or Xt libraries.  It can use 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 contact me by
email: derekn@foolabs.com .


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

Xpdf is developed and tested on a Linux 2.0 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, pdfimages)
can also be compiled on Win32 systems.  See the xpdf web page for
details.

If you compiled 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, and BeOS.  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 three additional utilities (which are fully described in
their man pages):

  pdfinfo -- dumps a PDF file's Info dictionary (plus some other
             useful information)
  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.).


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.

For Japanese support, you will need a Japanese font of the form:

    -*-fixed-medium-r-normal-*-NN-*-*-*-*-*-jisx0208.1983-0

and an X server that can handle 16-bit fonts.

If compiled with t1lib support, xpdf will use t1lib to render embedded
Type 1 and Type 1C fonts.  In addition, xpdf can be configured to use
t1lib for the base 14 fonts and for substituted fonts.  To enable this
feature, you must set an X resource for each Type 1 font file.  For
example:

    xpdf.t1TimesRoman:           /usr/local/fonts/Times-Roman.pfa
    xpdf.t1TimesItalic:          /usr/local/fonts/Times-Italic.pfa
    xpdf.t1TimesBold:            /usr/local/fonts/Times-Bold.pfa
    xpdf.t1TimesBoldItalic:      /usr/local/fonts/Times-BoldItalic.pfa
    xpdf.t1Helvetica:            /usr/local/fonts/Helvetica.pfa
    xpdf.t1HelveticaOblique:     /usr/local/fonts/Helvetica-Oblique.pfa
    xpdf.t1HelveticaBold:        /usr/local/fonts/Helvetica-Bold.pfa
    xpdf.t1HelveticaBoldOblique: /usr/local/fonts/Helvetica-BoldOblique.pfa
    xpdf.t1Courier:              /usr/local/fonts/Courier.pfa
    xpdf.t1CourierOblique:       /usr/local/fonts/Courier-Oblique.pfa
    xpdf.t1CourierBold:          /usr/local/fonts/Courier-Bold.pfa
    xpdf.t1CourierBoldOblique:   /usr/local/fonts/Courier-BoldOblique.pfa
    xpdf.t1Symbol:               /usr/local/fonts/Symbol.pfa
    xpdf.t1ZapfDingbats:         /usr/local/fonts/ZapfDingbats.pfa


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.

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
----

This release of xpdf should improve the situation with embedded
fonts.  However, Type 3 and TrueType fonts are still not handled.

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 and Martin P.J. Zinser 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.


References
----------

Adobe Systems Inc., _Portable Document Format Reference Manual_.
Addison-Wesley, 1993, ISBN 0-201-62628-4.
[The printed manual for PDF version 1.0.]

Adobe Systems Inc., _Portable Document Format Reference Manual_,
Version 1.3.  March 11, 1999.
http://partners.adobe.com/asn/developer/PDFS/TN/PDFSPEC.PDF
[Updated manual for PDF 1.3.]

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

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 font support.]

Adobe Systems, Inc., _Adobe-Japan1-2 Character Collection for
CID-Keyed Fonts_ (Bitmap Character Image Version), Adobe Developer
Support Technical Note #5078-b.  1994. 
http://www.adobe.com/supportservice/devrelations/PDFS/TN/5078b.pdf
[The complete Adobe Japanese 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.]

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.]

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.]

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.]

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".
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.]

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

"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.]
