Here's an article that describes how to perform basic photo manipulations using Apple's iPhoto app on iOS devices like iPhone and iPad. Tasks include rotate, straighten and crop images, exposure adjustment, and color correction. iPhoto has more advanced features, too. iPhoto for iOS costs $5 through the iTunes Store.
http://www.macworld.com/article/1166001/how_to_make_basic_edits_in_iphoto_for_ios.html
http://www.macworld.com/article/1166001/how_to_make_basic_edits_in_iphoto_for_ios.html