How to install GIMP 2.7?

If you cannot wait, according to this: http://www.gimp.org/downloads/ you should download and install from source: ftp://ftp.gimp.org/pub/gimp/v2.7/

The simple answer is - install the stable 2.8 instead! Fortunatelly it also made gimp plugin registry (with the famous save for web plugin) easy to install.

Via http://www.webupd8.org/ :

GIMP 2.8 stable installation

If you're upgrading from an older GIMP version please visit the link and pay attention to the 'dist-upgrade' command http://www.webupd8.org/2012/05/gimp-28-stable-finally-available-for.html (also if you want to revert to GIMP 2.6.x)

If you're just installing GIMP for the first time on your current system install:

sudo add-apt-repository ppa:otto-kesselgulasch/gimp
sudo apt-get update
sudo apt-get install gimp

GIMP Plugin Registry for GIMP 2.8 installation

http://www.webupd8.org/2012/05/install-gimp-plugin-registry-for-gimp.html

sudo add-apt-repository ppa:otto-kesselgulasch/gimp
sudo apt-get update
sudo apt-get install gimp-plugin-registry