Most image forensics have been done in a way called "copy and paste", which means part of the image is copied from another part of it. A site named <a href="http://www.pskiller.com/" rel="nofollow">Photoshopped Image Killer</a> can detect such kind of image forgery very well. It identifies the forgery by detecting repetitions in the digital bits that comprise the image�even if those repetitions are too subtle for the eye to detect or damaged by image compressions like JPEG.