Abstract
Digital image forgery detection becomes an important research topic in digital image forensics. JPEG is a popular file format for digital image now. DCT transformation and quantization are two main parts of JPEG encoding process. Quantization table is used for quantizing the DCT coefficients and has been proved as an effective feature for image forgery detection. In this thesis, we propose a method to detect image forgery by detecting inconsistency of JPEG encoded blocks. First, we estimate the quantization table of a JPEG compressed image. Then, we measure the block quantization error using estimated quantization table. Finally, we detect the forged region with large block quantization error by thresholding. In the experimental results, we show that our proposed quantization table estimation method outperforms the existing methods and our proposed image forgery detection algorithm performs well in different forgery type, including copy-move, splicing, image inpainting, image resizing, cropping, and recompression.