FotoForensics uses an advanced algorithm to decode any possible photoshopped pictures and manipulation; it uses the Error Level Analysis (ELA) to identify areas within an image that are at different compression levels. With JPEG images, the entire picture should be at roughly the same error level. If a section of the image is at a significantly different error level, then it likely indicates a digital modification.
An original digital photograph
Some books are duplicated to the right and left of the original book and a toy dinosaur was inserted into the photo.
The resaved image was digitally modified: books were copied and a toy dinosaur was added. ELA clearly shows the modified areas as having higher ELA values.
Alternatively, JPEGsnoop yet another great freeware. Since it runs on your computer, it doesn’t come with the 5MB file size limit of FotoForensics. It is more of a data analyzer than a image manipulator analyzer. JPEGsnoop is a detailed JPEG image decoder and analysis tool. It reports all image metadata and can even help identify if an image has been edited.
Another good example is a movie poster for some “end of the world” movie. As seen in the image below, the Statue of Liberty was photoshopped into the foreground and the storm was digitally enhanced in Adobe Photoshop.