Exposing Digital Forgeries From JPEG Ghosts

When creating a digital forgery, it is often necessary to combine several images, for example, when compositing one person´s head onto another person´s body. If these images were originally of different JPEG compression quality, then the digital composite may contain a trace of the original compression qualities. To this end, we describe a technique to detect whether the part of an image was initially compressed at a lower quality than the rest of the image. This approach is applicable to images of high and low quality as well as resolution.