Mirroring a map

Isn't there a program that u make 1/2 or part of the map, and then u can mirror it over to the other side? Because quite frankly, I dont want to spend double the time making the map. And it would make it exactly perfect, anyone have any apps for it?|||Look in the useful information sticky. There are links to some tutorials, and some of the height map instructions tell you how to do it in photoshop or similar programs.|||http://forums.gaspowered.com/viewtopic.php?t=19498