Ouch, a real mis-match of packages. You have been using the Rob Savoury PPA and ...maybe something else
The first thing to do is disable the Rob Savoury PPA (2) in Synaptic The Settings - Repositories section. Untick the Rob Savoury entries. If you ok that Synaptic will remind you to refresh the package list. Click the reload button to refresh the package list. Now go to the libgegl entry and try a re-install. I am not sure where the 4.34 (now) (1) entry comes from but the PandaJim version (3) should now register as the most recent and take precedence.
The first thing to do is disable the Rob Savoury PPA (2) in Synaptic The Settings - Repositories section. Untick the Rob Savoury entries. If you ok that Synaptic will remind you to refresh the package list. Click the reload button to refresh the package list. Now go to the libgegl entry and try a re-install. I am not sure where the 4.34 (now) (1) entry comes from but the PandaJim version (3) should now register as the most recent and take precedence.