Research Of Digital Image Forensics Based On The Lighting Conditions

As the development of modern digital technology, various powerful tools for digitalimage processing come out and they give people a lot of convenience. Meanwhile, theseadvanced tools are also ultilized by some unruly elements. The malicious tampering of theimage often happens. It hinders people from knowing the truth and causes many socialproblems. Therefore, the research of digital image forensics technology is important andvaluable.The process of synthesizing a new image from different images is a common mannerof image tampering. Because the light environment in which different photos are shot isnot identical, the lighting effects of the characters in the synthetic images are reached theconsistent difficultly. The illumination inconsistencies which exist in the synthetic imagecan be used as an evidence of identifying whether the image is tampered or not.In this thesis, the study focuses on the light inconsistencies for image forensics andthe main contributions are as follows:(1) Analyzed the light direction and illuminant color which is related to lightinconsistencies and stated the reason of being the evidence of identifying whether theimage is tampered or not. Then, discussed several typical methods of estimating lightdirection and illuminant color, analyzed the advantages and disadvantages of thesemethods in algorithm performance and applicability.(2) Proposed an improved method for estimating light direction and improved thelight model which made more accurate estimates of the light direction.(3) Proposed an improved method for estimating illuminant color. Without theprocess of image segmentation, the method reduces the error brought by the imagesegmentation and improves the estimation accuracy of the illuminant color.