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pdfalto

Build Status SWH License: GPL v2

pdfalto is a command line executable for parsing PDF files and producing structured XML representations of the PDF content in ALTO format, capturing in particular all the layout and style information of the PDF.

pdfalto is initially a fork of pdf2xml, developed at XRCE, with modifications for robustness, addition of features, improved layout element detections, and output enhanced format in ALTO (including in particular space information, useful for instance for further machine learning processing). It is based on the Xpdf library.

The latest stable version is 0.4. Working version (master) is 0.5.

An Archlinux package for pdfalto is available here, thanks to @andreasbaumann. The build process described below will create a portable standalone pdfalto executable that can be packaged with other tools without further installation requirements for the end-user.

Requirements

Usage

General usage is as follow:

Usage: pdfalto [options] <PDF-file> [<xml-file>]
  -f <int>                      : first page to convert
  -l <int>                      : last page to convert
  -verbose                      : display pdf attributes
  -noImage                      : do not extract Images (Bitmap and Vectorial)
  -outline                      : create an outline file xml
  -annotation                   : create an annotations file xml
  -noLineNumbers                : do not output line numbers added in manuscript-style textual documents
  -readingOrder                 : blocks follow the reading order
  -noText                       : do not extract textual objects (might be useful, but non-valid ALTO)
  -charReadingOrderAttr         : include TYPE attribute to String elements to indicate right-to-left reading order (might be useful, but non-valid ALTO)
  -fullFontName                 : fonts names are not normalized
  -nsURI <string>               : add the specified namespace URI
  -opw <string>                 : owner password (for encrypted files)
  -upw <string>                 : user password (for encrypted files)
  -filesLimit <int>             : limit of asset files be extracted
  -q                            : don't print any messages or errors
  -v                            : print version info
  -h                            : print usage information
  -help                         : print usage information
  --help                        : print usage information
  -?                            : print usage information

In addition to the ALTO file describing the PDF content, the following files are generated:

Extra script to get only text content

The goal of pdfalto is to extract all the content of a PDF, not just text, but also layout, style, font, vector graphics, embedded bitmap, annotation, metadata, and outline information. For convenience and debugging, we provide a simple XSLT to extract only the text content from the produced ALTO XML file. For instance, using xsltproc command line, the following outputs the text content only:

xsltproc schema/alto2txt.xsl alto_file.xml

Dependencies

Dependencies can be recompiled by running this script

./install_deps.sh

The script will download and build the dependencies unders libs/ and the additional language support packages for xpdf under languages/.

If necessary, see compiling dependencies procedures for further details.

Known issues

(issue 41) might occur while building, in this case you'll need to compile the dependencies before building pdflato.

Build

git clone https://github.com/kermitt2/pdfalto.git && cd pdfalto

git submodule update --init --recursive

cmake .

make

The executable pdfalto is generated in the root directory. Additionally, this will create a static library for xpdf-4.03 at the following path xpdf-4.03/build/xpdf/lib/libxpdf.a and all the libraries and their respective subdirectory.

To use the additional xpdf language support packages, the executable pdfalto comes with a config file xpdfrc and language resources installed under languages/. Both xpdfrc and languages/ must be alongside the executable pdfalto to be used. To add pdfalto with these additional resources to a third party application (e.g. GROBID), move the executation together with these files:

lopez@work:~$ ls my_pdfalto/
languages  pdfalto  xpdfrc
Known issues

(issue #135) on macOS "fontconfig.h file not found" might occur while building, see described workaround.

Future work

Changes

New in version 0.4 (apart various bug fixes):

New in version 0.3 (apart various bug fixes):

New in version 0.2 (apart various bug fixes):

New in version 0.1 (apart various bug fixes):

Contributors

Contact: Patrice Lopez (patrice.lopez@science-miner.com)

pdfalto is developed by Patrice Lopez (patrice.lopez@science-miner.com) and Achraf Azhar (achraf.azhar@inria.fr).

pdf2xml is orignally written by Hervé Déjean, Sophie Andrieu, Jean-Yves Vion-Dury and Emmanuel Giguet (XRCE) under GPL2 license.

Xpdf is developed by Glyph & Cog, LLC (1996-2017) and distributed under GPL2 or GPL3 license.

The windows version has been built originally by @pboumenot and ported on windows 7 for 64 bit, then for windows (native and cygwin) by @lfoppiano and @flydutch.

License

As the original pdf2xml and main dependency Xpdf, pdfalto is distributed under GPL2 license.

Useful links

Some tools for converting ALTO into other formats: