I am a fairly new Xournal user and found it useful for drawing quick sketches
of diagrams and the like for the LaTeX document I was working on. To do that,
I wrote a small tool, which reads Xournals .xoj files and generates TikZ 
code from them.
It does not support all features of the xoj file format (yet), but it serves
its purpose very well. It supports removing redundant parts of strokes, can
detect circles and rectangles to write them in the tikz file as such and it
even features pressure sensivity.
The tool is built around a collection of python modules (named xojtools),
which are very modular and are designed to be useful for other xournal-file-
parsing python projects.
Possible other tools I could imagine are for example
* xoj2tex to convert an entire multi-page xournal file with a pdf as the
background to a LaTeX file. The pdfpages package might come in handy 
* xoj2pst to convert a sketch to pstricks ... if anyone still uses that ;-)
* xoj2pdf as an extension to xoj2tex to create pdf file right away. That
might create smaller output files than Xournals PDF export?
* xoj2ascii ... just kidding
Patches and Feedback are always welcome, just clone it on
or download the latest release in the download section 
I hope someone else will find this as useful as I do.
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