Research On Passive Digital Image Forensics Based On Image Content

With the development of the computer technology, digital image processing technology, as one branch of computer science, is developing fast. New technology and new software of image processing have come forth with more convenient manipulation. More and more people can modify the pictures only with a computer and image processing software such as Photoshop and 3DMAX. A modified picture can not be recognized by eyes because of lacking of the tampering traces. Passive image forensics has been developed which detects the image by many methods to find out the fact whether the picture is modified or not. Meanwhile, it can also tell us that the picture is natural image or a computer generate.The most difference between passive image forensics and active one is that digital signature and digital watermark should be embedded in images in advanced in active forensics. The passive forensics uses the information which is applied by the indeed images. Then, the passive one will have more applications.This paper reveals the research on passive image forensics based on image content. The main achievements reveal as following:Aiming at the question that there is no acknowledged theoretical framework of passive forensics, it gives a preliminary framework.Aiming at the problems that every method revealed is detecting one certain tamper, there is no one certain classification method. Then it classified all methods into three classifications which are passive forensics based on image content, passive forensics based on the capturing process and passive forensics based on physical principles.Aiming at edge flurring, the general manipulation in image tampering, a new algorithm has been applied which uses fuzzy enhancement and rough sets to find out the edges which is flurred manually. The result shows the algorithm works well.Applying projection data to passive image forensics, a new algorithm is more rapid than Posucue’s algorithm. Furthermore, it improves the algorithm by replacing horizontal/vertical projection to Ring projection which makes the algorithm rotation invariant and robust to illumination.ASIFT algorithm has been applied in detection the copy-paste forgery at the first time. The result shows that the algorithm can work well when the image rotates and large scale changes. LLE algorithm has been applied in detection the copy-paste forgery at the first time. LLE is some robust to edge flurred. An improved LLE shows that the improved one is more rapid than original LLE.Finally, the paper summarized the research works and gave the prospect of passive image forensics in future.