title: An improved parameter estimation scheme for image modification detection based on DCT coefficient analysis.
abstract: Most of the existing image modification detection methods which are based on DCT coefficient analysis model the distribution of DCT coefficients as a mixture of a modified and an unchanged component. To separate the two components, two parameters, which are the primary quantization step, Q1, and the portion of the modified region, α, have to be estimated, and more accurate estimations of α and Q1 lead to better detection and localization results. Existing methods estimate α and Q1 in a completely blind manner, without considering the characteristics of the mixture model and the constraints to which α should conform. In this paper, we propose a more effective scheme for estimating α and Q1, based on the observations that, the curves on the surface of the likelihood function corresponding to the mixture model is largely smooth, and α can take values only in a discrete set. We conduct extensive experiments to evaluate the proposed method, and the experimental results confirm the efficacy of our method.
authors.affiliation: School of Computer Science and Technology, Harbin Institute of Technology, Harbin 150080, China; School of Software, Harbin University of Science and Technology, Harbin 150080, China.
authors.forename: Liyang
authors.initials: L
authors.lastname: Yu
authors.affiliation: School of Computer Science and Technology, Harbin Institute of Technology, Harbin 150080, China. Electronic address: qi.han@hit.edu.cn.
authors.forename: Qi
authors.initials: Q
authors.lastname: Han
authors.affiliation: School of Computer Science and Technology, Harbin Institute of Technology, Harbin 150080, China. Electronic address: xm.niu@hit.edu.cn.
authors.forename: Xiamu
authors.initials: X
authors.lastname: Niu
authors.affiliation: Department of Computer Science, The University of Hong Kong, Hong Kong.
authors.forename: S M
authors.initials: SM
authors.lastname: Yiu
authors.affiliation: Department of Optoelectronic Engineering, Jinan University, Guangzhou, China.
authors.forename: Junbin
authors.initials: J
authors.lastname: Fang
authors.affiliation: School of Electronics and Information Engineering, Harbin Institute of Technology, Harbin 150080, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhang
keywords: DCT coefficient analysis; Digital image forensics; Image forgery detection; Primary quantization step estimation