It was a staple of the regimes of the Cold War to doctor photographs. Winston's job at the Ministry in 1984 was rewriting history using such photographs. There is a good, though out of print, work by David King The Commissar Vanishes, which details Stalinist photo techniques.
See the online exhibit at the Newseum
Now the BBC has reported similar manipulations of recent photos of North Korean leader Kim Jong-il in their story: 'Fake photo' revives Kim rumours