installing pdftohtml from sources – successfully using 0.40a

• pdftohtml-0.40a.tar.gz (an experimental version from 2006-11-06 on SourceForge.net)
• as opposed to 0.39 I got this recompiled out of the box on Linux and Mac OS X Lion

True, this is not brand-new information, but I think still worth mentioning.

table_pdf2csv.pl : extracting tables from PDF, saving them as CSV

• I leave the PDF extraction bit to "pdftohtml -xml".
• My perl scripts tells you, at what "physical columns" text gets found within the PDF file.
• You choose, which "physical columns" really makes sense to you as logical column starters.
• Now you run my perl script with those few serious physical columns specified,
  and it creates a CSV file for you.
• Per logical row a few physical rows got created.
• If you want, you can merge cells from neighboring rows into logical cells,
  you can use LibreOffice Calc, or OpenOffice Calc, or Excel for this step.

Does this sound interesting to you?

PDF harvesting – automatic extraction of information from PDF files

Why and what for ...

There may be a lot of structured information available in a PDF file (I assume), just as in web pages, and I was thinking about also making use of that information.
Of course I owe you here a discussion of what structured information, we might wish to get hold on, and maybe I am going to add this here one day, but for the time being I will just focus on tables.

For web pages i.e. HTML pages there are a couple of harvesting techniques out there.
I am focusing here on table extraction, and for HTML table extraction I want to refer you to another blog article of mine.
HTML table extraction looks like solved to me, PDF table extraction doesn't.
I think, there isn't as much meta-information left in PDF files as there is in HTML. I would rather appreciate, if somebody proves me wrong there, but I rather suspect, that's the way it is. I am still a little optimistic, that tables can get recognized in PDF files.

Update 2011-07-03:

• all these approaches cost me far too much effort already
• I don't regard them production ready
• of course it's possible to extract tabular information from PDF files
• if you do want to get at it yourself (with specific software, i.e. your own code), make use of "pdftohtml -xml"

Update 2012-01-09:

• read my latest (2012-01) article(s) tagged pdftohtml!
• I created some software, that extracts tables from PDF and saves them as CSV
• the heuristics for recognizing the tables are not in the software, rather does the user have to specify the physical x-positions – but that's not too hard, and the software supplies the user with all necessary and valuable details

pdf2table
2010-10-10 :

• in contact with the author
• created Apache Ant build files, managed to build the software on Linux
• managed to run the software
• the software actually runs "pdftohtml -xml"
• the software attempts to recognise table using some heuristics and creates an XML file with the tables recognised, but it fails far too often for my taste
• created RNC for that XML file
• corrected that XML file, optimized it slightly for further processing
• created a simple shell script to wrap the Java class
• …

This looked rather promising to me. But actually I encountered too many obstacle.
The only benefit from my attempts here: I got quite familiar with "pdftohtml -xml", which I have been using a lot lately.

tableseer

2010-10-10 :

• in contact with the maintainer on sourceforge and also with the authors
• the software comes with Apache Ant build files
• but I don't manage to run the software
• …

Links and ressources

• http://ieg.ifs.tuwien.ac.at/projects/pdf2table/
  (GNU license, apparently "sleeping" since 2006)
  seems to apply heuristics to recognize tables and delivers XML for that;
  I am going to try this out rather soon
• http://tableseer.sourceforge.net/
  …
• http://www.convertzone.com/comparepdf2txt.htm
  (commercial, apparently "sleeping" since 2003)
  I will only spend my time and no money on these experiments, so I doubt I will be able to try this software out.
• …

"pdftohtml" vs. DRM

A project of mine involves extracting strings and other details from PDF files using "pdftohtml -xml".

A plain "pdftohtml -xml" refuses to read PDF files with set copy-protection bits set. But if you add "-nodrm" on the command line, it reads them anyway, but it mentions the problem on STDERR.