【作者】 岳红原；

【导师】 黄继风；

【作者基本信息】 上海师范大学 ， 计算机应用技术， 2006， 硕士

【摘要】 由于功能强大的图像处理软件的广泛使用，数字图像越来越容易被篡改。现在，向图像中加入或从图像中移除某些重要的人或物，同时不留下明显的篡改痕迹已经成为可能。当数字相机和数字摄像机代替了传统的模拟相机和摄像机时，对数字图像的鉴别，图像内容的确认以及篡改的探测的需求就变得越来越迫切了。传统上，在鉴别图像真伪时，采用事先在数字图像中嵌入数字水印或签名的方法。但是，此方法存在着诸多的缺陷和不足。针对没有嵌入数字水印或签名的篡改图像，对其进行真伪的鉴定，成为新的研究方向。 一幅被改动过的数字图像可能用肉眼无法辨别真伪，但常常会因为篡改而留下一些不可见的线索。篡改会干扰图像一些潜在的统计特性。基于这样的设想，针对不同的图像篡改方式，本文提出了二种检测篡改图像的方法： (1)基于双JPEG压缩统计特性的检测方法。这种方法是通过检测双JPEG压缩图像的图像块先前的量化系数来实现的。首先，定义了在两次压缩时，出现在特定位置上的DCT系数直方图的一些特性。然后，使用支持向量机来估计双压图像的初始的量化系数，有不同量化系数的图像块便是值得怀疑的区域。最后，基于大量不同的双压图像集，用一系列的实验来验证本方法的性能及可靠性。 (2)基于图像匹配的检测方法。此检测方法着重针对复制图像本身的一部分来遮盖另一重要部分的篡改类型(复制遮盖篡改)，针对不同尺寸大小的篡改图像提出了两种检测算法，并论证了检测算法的有效性和可靠性。这些方法对于复制区域被增强或修饰使之融入到背景之中，依然非常有效。 对于每一种方法，都论述了它的理论基础，并在实验结果中，展示了它在检测篡改图像时的有效性。更多还原

【Abstract】 As a result of the widespread use of powerful image-processing software, it is increasingly easier to tamper digital images. For the time being, it has been possible to add or remove some important people or things to or from an image, leaving behind no obvious traces at the same time. Since digital cameras and digital vidicons replaced traditional analogue counterparts, it has become more and more urgent to identify digital images, to confirm image contents and detect their tampering. The traditional method to distinguish true or false images is to embed digital watermarks or signatures in digital images in advance. However, it still has a lot of weaknesses. Therefore it forms a new research direction to authenticate digital images that are embedded with no digital watermarks or signatures.Probably, an altered digital image cannot be authenticated. But, more often than not, some invisible clues may be left in the tampering process, because the tampering may disturb some underlying statistical properties of images. On account of this assumption, we propose two methods to detect tampered images in terms of different tampering forms:(1) A detection method based on the statistical properties of double-JPEG compression. This approach is used to detect previous quantification coefficients of double-JPEG compressed image pieces. First, identify some features of DCT histograms of particular coefficients due to double compression. Second, use SVM to estimate the original quantification coefficients from double-compressed images. The image areas with different quantification coefficients are worth our questioning. Finally, basing on many different sets of double-JPEG compressed images, use a series of experiments to verify the performance and reliability of this method.(2) A detection method based on image matching. This detection method focuses on the tampering type which is copying an image area then moving it to cover other important parts (Copy-Move forgery image). According to tampered image’s sizes, two checking algorithms are put forth and their effectiveness and accountability are更多还原