Synfig is a powerful, industrial-strength vector-based 2D animation software package, designed from the ground-up for producing feature-film quality animation with fewer people and resources.
The software is capable of simulating soft-shading using curved gradients within an area so that the animator doesn’t have to draw shading into every single frame. There is also a wide variety of other real-time effects that can be applied to layers or groups of layers like radial blurs, color tweaks that all are resolution-independent. Other features include the ability to control and animate the width of lines at their individual control points, and the ability to link any related data from one object to another. Synfig also works with High Dynamic Range Imaging.
Synfig can be downloaded from the developers website or simply be installed by the following command in a terminal window:
sudo apt-get install synfig