Image Splicing Forgery
Hany Farid, Snopes, 29a.ch
In image splicing, a segment within the source image is copied and pasted into the target image. Spliced image possess various artifacts for example, differing noise patterns, multiple color distributions and abnormal dynamic range. This is because of the fact that the image is spliced using segments from the source image having different noise, dynamic range and color distribution than the target image and introduces irregularities within the source image's statistics. Sometimes, after splicing images, different post-processing operations are applied to make the changes imperceptible, for example, blurring around the spliced region, or double JPEG compression while saving the edited image again.
The image shown above is an example of image splicing forgery is shown. Image on the right is forged version of the image on the left (taken from a Hollywood movie, "Black Hawk Down"). This image was shared widely on the internet after the assassination of Osama Bin Laden.