If you're using the python version, you can install using pip:
$ sudo pip install lib2d
For C users download the source code or use mercurial and build manually:
$ hg clone https://bitbucket.org/jlm/lib2d $ cd lib2d $ mkdir build; cd build $ cmake .. $ make -j && sudo make install
demos folder contains some projects to help get you started.
The core of lib2d is meant to be ludicrously simple in scope, with optional extensions providing additional functionality. Some planned extensions are:
Drawable (Python, C)members.