Install necessary tools and dependencies:

Code:
sudo apt-get install git build-essential libgtk2.0-dev libpango1.0-dev libgdk-pixbuf2.0-dev libglib2.0-dev libcairo2-dev libfreetype6-dev fontconfig libdbus-glib-1-dev liblcms2-dev libpng12-dev libjpeg-dev libpoppler-dev libpoppler-glib-dev libtiff4-dev libwebkit-dev libmng-dev librsvg2-dev libwmf-dev zlib1g-dev libbz2-dev libgs-dev libaa1-dev libjasper-dev python-dev python-gtk2-dev libtool autoconf automake libexiv2-dev openexr libopenexr-dev exrtools dcraw libopenraw-dev libsdl1.2-dev graphviz libgraphviz-dev libavformat-dev libspiro-dev libumfpack5.4.0 enscript ruby-dev liblua5.2-dev gtk-doc-tools libgudev-1.0-dev libexif-dev libxpm-dev
Then fetch the dependencies you need to build:
Code:
git clone git://git.gnome.org/babl
git clone git://git.gnome.org/gegl
and build them:
Code:
cd babl
./autogen.sh --prefix=$HOME/build
make
make install
cd ..

cd gegl
PKG_CONFIG_PATH=$HOME/build/lib/pkgconfig ./autogen.sh --prefix=$HOME/build
make
make install
cd ..
Get the gimp source. CHOOSE ONE:

EITHER, download and unpack the tarball (recommended):
Code:
wget ftp://ftp.gimp.org/pub/gimp/v2.8/gimp-2.8.0.tar.bz2
tar xvfj gimp-2.8.0.tar.bz2
cd gimp-2.8.0
OR clone the git repo and check out 2.8.0:
Code:
git clone http://git.gnome.org/cgit/gimp
cd gimp
git checkout GIMP_2_8_0
Now, build it gimp:
Code:
PKG_CONFIG_PATH=$HOME/build/lib/pkgconfig ./autogen.sh --prefix=$HOME/build
make
make install
That's it. Now you can run gimp-2.8 like this:
Code:
LD_LIBRARY_PATH=$HOME/build/lib $HOME/build/bin/gimp-2.8
Let me know if anything needs fixing. The install list can definitely be trimmed.