G'MIC (Greyc's Magic for Image Computing) is a complete framework for image processing. It is popular for being combined as plugin for GIMP to process awesome images. G'MIC gives GIMP more hundreds of image filters. To install it in Ubuntu, make sure you have GIMP installed then perform this command:

sudo apt-get install gimp-gmic
In Ubuntu 14.04 32 bit, it needs about 2 MB to download packages. After installing, restart running GIMP to see changes. To see G'MIC interface inside GIMP, open menu Filter > G'MIC.