Copymove by John Graham-Cunning detects image manipulations which have been created with the clone tool.
NEW: GIMP plugin added. Compile and install with:
$ CC=g++ CFLAGS=-O3 LIBS=-lpthread gimptool-2.0 --install elsamuko-copy-move.c
You will find the plugin then under Image->Copy Move.
NEW2: W32 version added.
Update1: Linux version with multithreading and can be used for bigger images now.
Update2: Massive speed gain thanks to the hint of Luca Del Tongo:
The calculation only uses the lower frequencies of the DCT now.
Update3: Ignoring "boring" regions while comparison, e.g. where second and third DCT rings are zero.
Original (cc from Mark Hogan):
Cloned out sign:
$ ./copymove warning_clone.jpg 2 10
Result: Manipulation detected :D
Y. Huang, et al., Improved DCT-based detection of copy-move forgery in images, Forensic Sci. Int.