fatal error: png.h: no such file or directory

source : http://stackoverflow.com/questions/9829175/pip-install-matplotlib-error-with-virtualenv
Building Matplotlib requires

libpng

(and

freetype

, as well) which isn't a python library, so

pip

doesn't handle installing it (or

freetype

).

You'll need to install something along the lines of

libpng-devel

and

freetype-devel

(or whatever the equivalent is for your OS).

See the building requirements/instructions for matplotlib.

To generate graph in png format you need to Install following dependent packages

sudo apt-get install libpng-dev

sudo apt-get install libfreetype6-dev