【作者】 郭一平；

【导师】 孔祥维；

【作者基本信息】 大连理工大学 ， 信号与信息处理， 2009， 硕士

【摘要】 随着数字图像的广泛应用,其真实性的鉴别成为了一个研究的热点问题,图像处理软件越来越多,技术也越来越复杂精细,使得更多的人能够轻易地对图像进行篡改。篡改手段的多样化使得数字图像取证工作更加艰难,目前已有很多学者针对图像篡改过程如复制-粘贴、模糊、尺度变换等操作提出了多种方法对其进行检测,从而对数字图像的真实性做出鉴别。数字图像压缩历史检测是数字图像取证的一个重要的组成部分,通过判断图像之前是否经过压缩,可对数字图像的真实性作出一个初步的判断,可作为数字图像取证的辅助决策。本文在这一研究背景下对数字图像压缩历史的分析与检测进行了深入的研究,主要的研究成果如下:(1)对数字图像压缩历史检测进行了全面系统的介绍,包括研究背景和研究现状等,并对现有的几种检测技术包括无损图像的压缩历史检测和有损压缩图像的重压缩检测进行详细的介绍和分析,更重要的是将数字图像压缩历史的分析与检测融入到数字图像取证研究中,分析了其在数字图像取证领域的应用包括检测合成篡改、隐密分析和图像来源等。(2)在深入研究分析JPEG压缩原理及其对数字图像JPEG系数的影响的基础上,提出了基于图像信息损失量的无损图像压缩历史检测算法。本文通过将待测图像剪切四行四列来估计原始图像,并提出使用图像信息损失量来度量图像的信息损失及与原始图像的相似程度,通过提取统计特征,利用Fisher线性分类器和阈值分割方法对图像进行压缩历史检测。实验结果表明,该算法受图像内容影响很小,而且能够不经训练测试就能够对单幅图像进行准确判断。(3)针对JPEG压缩图像重压缩检测方面,在以往重压缩检测算法的基础上,提取了能够反映重压缩特性的直方图特征、DFT特征、Benford特征和Markov特征,在实际应用中,图像的原始压缩质量因数未知,因此不同于以往的文献中采用的一对一的测试方法,本文分别对这几种特征进行原始压缩质量因数不同的混合训练和测试,对其实验结果进行分析和比较。更多还原

【Abstract】 The authentication of digital images is attracting more and more attention from researchers. Along with the wide use of image processing softwares, it becomes more easily for people to tamper the image content which makes image forensics much harder. A lot of methods have been proposed to detect tampering process such as copy-paste, blurring, scale transformation and so on.As an important part of digital image forensics, digital image compression history detection can be used to make a first judgment of the authenticity of images. Under this circumstance, this paper focuses on the research of compression history analysis and detection of digital images. The main contribution of this thesis includes:(1) The paper gives a comprehensive introduction to the compression history detection of digital images including the researching background and existing technical literatures on the compression history detection of lossless images(BMP) and loss compressed images(JPEG). Furthermore, the paper applies the analysis and detection of image compression history to image forensics such as copy-paste detection, steganalysis and image source determination.(2) The approach of deting compression history of BMP images based on image information loss is proposed in this paper. Through analyzing the effect of JPEG compression to JPEG coefficients, statistical features reflecting image information loss difference of the detected image and the estimated image can be extracted. Thus using Fisher linear classifier and threshold division the compression history of BMP images are detected in this paper. Experiments show that the detection accuracy of the proposed approach is high, and not affected by image contents compared to Benford methods. It can also make an accurate judge of the compression history of a single BMP image without training.(3) The paper exacted features which can reflect the double compression effect including histogram features, DFT features, Benford features and Markov features of JPEG coefficients based on previous double compression detection algorithms. The original compression quality of images is usually unkown in practical use, therefore, different from exisiting literatures which use one-to-one test methods, this paper did some experiments on mixed image database with different original compress quality and comparade the results using different features.更多还原