Discrimination of Computer Synthesized or Recaptured Images from Real Images

An image that appears to be a photograph may not necessarily a normal photograph as we know it. For example, a photograph-like image can be rendered by computer graphics instead of being taken by a camera or it can be a photograph of an image instead of a direct photograph of a natural scene. What is really different between these photographic appearances is their underlying synthesis processes. Not being able to distinguish these images poses real social risks, as it becomes harder to refute claims of child pornography as non-photograph in the court of law and easier for attackers to mount an image or video replay attack on biometric security systems. This motivates digital image forensics research on distinguishing these photograph-like images from true photographs. In this chapter, we present the challenges, technical approaches, system design and other practical issues in tackling this multimedia forensics problem. We will also share a list of open resources and the potential future research directions in this area of research which we hope readers will find useful.