Ubuntu running `pip install` gives error 'The following required packages can not be built: * freetype'

When performing `pip install -r requirements.txt`, I get the following error during the stage where it is installing `matplotlib`: REQUIRED DEPENDENCIES AND EXTENSIONS numpy: yes [not found. pip may install it below.] dateutil: yes [dateutil was not found. It is required for date axis support. pip/easy_install may attempt to install it after matplotlib.] tornado: yes [tornado was not found. It is required for the WebAgg backend. pip/easy_install may attempt to install it after matplotlib.] pyparsing: yes [pyparsing was not found. It is required for mathtext support. pip/easy_install may attempt to install it after matplotlib.] pycxx: yes [Couldn't import. Using local copy.] libagg: yes [pkg-config information for 'libagg' could not be found. Using local copy.] freetype: no [pkg-config information for 'freetype2' could not be found.] ... The following required packages can not be built: * freetype Shouldn't `pip install -r requirements.txt` also install freetype? How should freetype be installed in Ubuntu 12.04 so it works with `matplotlib`?