Here is a guide to install Gimp 2.8 on using the otto06217 PPA on Ubuntu 12.10.
GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching, image composition, and image construction. Read more about Gimp.
Before you can install Gimp you first need to add the otto06217 PPA. To add the PPA and install Gimp 2.8 open a terminal window (press Ctrl+Alt+T) and copy+paste the following lines:
sudo add-apt-repository ppa:otto-kesselgulasch/gimp
sudo apt-get update
sudo apt-get install gimp gimp-plugin-registry
When Gimp is installed you can close the terminal window.
To start Gimp press the SuperKey and type: gimp