基于变换域的数字水印技术

数字水印技术是将信息隐藏从而实现多媒体数据的版权保护,数字水印的研究主要是所提出的算法具有更好的不可见性和鲁棒性。提出了2种不同的变换域方法:一种是基于DCT域的水印算法,水印信息取自二值签名图像;另一种是基于小波分解的数字水印算法,采用服从高斯分布的随机数作为水印信息。实验结果表明,这2种水印算法具有良好的性能,实现的水印具有不可见性,而且对于常见的图像处理具有很好的鲁棒性。     

基于NSCT-DWT-Schur分解的盲检测数字水印算法

<正>数字水印技术是版权认证和保护的重要手段。为了提高盲检测数字水印算法的透明性和鲁棒性,实现二者较好的平衡,本文提出一种基于非下采样Contourlet变换（NSCT）,离散小波变换（DWT）和Schur分解算法的盲检测数字水印算法。该算法首先对载体图像进行二级NSCT变换,提取其低频子带,接着对得到的低频子带进行一级DWT变换,然后将DWT变换后得到的低频部分分块进行Schur分解并构建嵌入域,最后将扰乱加密的水印信息嵌入所得到的嵌入域中,实现水印的嵌入。实验结果显示,该方案可以实现水印的盲提取,能够较好地实现水印的透明性,并且对于常见的滤波、剪切等攻击具有较好的鲁棒性。     

基于DCT的自适应数字图像水印算法实现

数字水印技术已经成为信号处理领域的一个新的研究热点.首先介绍了数字图像水印技术,以及DCT算法的相关知识,并提出了一种新的数字水印加密算法,该算法可以根据图像大小产生相应的水印信息.利用Matlab对两幅图像进行了水印嵌入和提取的仿真实验,验证了该水印算法的有效性.     

基于角点特征的几何同步数字水印算法

对图像的角点检测与水印同步进行分析和讨论,在此基础上提出了一种基于角点特征的几何同步数字水印算法.为抵抗几何攻击,在归一化的图像中提取出较好的角点信息,重点分析了Harris与MIC角点检测的优缺点,将2种方法合并应用到角点检测,摒弃了单纯的像素信息修改,利用圆环的几何形状来统计表示水印信息.实验结果表明,所提出的水印算法较其他算法不仅能抵抗一般的图像攻击,而且在抵抗旋转、放缩等几何攻击方面的稳健性也有较好的提高.     

基于DWT和BEMD的图像水印嵌入算法

信息隐藏是信息安全的一个新的重要内容,数字水印技术是信息隐藏技术研究领域的重要分支.鲁棒性和隐藏性是数字水印技术的关键.本文提出了一种基于离散小波变换和二维经验模式分解的图像数字水印算法,在嵌入水印前把水印进行Arnold变换,把水印信息置乱,消除像素的空间相关性,从而提高了水印信息的安全性和鲁棒性.实验结果表明,该水...     

基于Krawtchouk不变矩的仿射攻击不变性局部水印算法

本文提出了一种基于原始图像Krawtchouk不变矩实现的仿射攻击不变性局部水印算法.具体介绍了Krawtchouk不变矩的构造方法,水印是事先产生的且与原始图像无关,通过将水印嵌入到图像的Krawtchouk不变矩中实现仿射攻击不变性.这种基于Krawtchouk矩的水印算法是局部水印技术,即水印的嵌入只是影响到部分原始图像,因此该算法对剪切攻击具有很好的鲁棒性.检测过程中采用独立分量分析技术实现真正意义上的盲检测.文中具体分析了所提出算法的计算复杂度,实验数据说明这种水印算法对通用水印测试软件Stirmark具有很好的鲁棒性.     

文本数字水印技术在电力物资供应链信息安全中的用研究

针对文本文档在电力物资供应各个环节传递中的信息安全问题,本文提出将文本数字水印技术用于文档信息安全保护中,结合文本数字水印技术在电力物资供应链中应用的需求,提出一种基于改变字符颜色完成水印信息嵌入的算法.该算法基于人类视觉系统（HVS）,通过微调字符颜色嵌入水印信息.对算法进行了仿真与攻击实验,实验结果表明,该算法具备较好的鲁棒性、透明性,且容量较大,同时可以实现针对对应属性的攻击进行篡改定位的能力,该算法具备一定的工程应用价值.     

数字水印擦除技术的研究

数字水印的嵌入和识别技术已有大量研究,然而数字水印的擦除算法却鲜有研究.数字水印的擦除技术是利用一定的算法和技术,对含有或未含水印的文件进行水印发现、水印清除和水印破坏的操作.从上述角度提出了逆向工程法、协议规范编码法、异构协议互斥法、转码互换法、二次水印法等五种方法和数据模型,并对每种方法的鲁棒性进行了分析.     

MPEG-2压缩域的视频数字水印新算法

视频数字水印技术是当前水印研究中的一个热点.本文提出一种视频数字水印新算法,直接对压缩后的视频数据流进行操作,根据运动矢量的特征值,将水印信息嵌入到运动矢量上,不需要完全解码和再编码过程.所提出的水印算法简单、有效,实现了水印盲检.与嵌入水印前的原视频图像相比,嵌入水印后的视频图像信噪比损失很小.     

基于矢量共享方案的数字水印分存算法

提出一种基于矢量共享方案的数字水印算法,将矢量共享的思想用于数字水印.算法在对水印信息隐藏前,对原始水印和分块水印都进行扰乱处理,同时分存也具有加密作用,算法具有很高的安全性.实验表明,算法还具有很好的隐藏效果和抗剪切功能.     

Geometry-based distributed scene representation with omnidirectional vision sensors

This paper addresses the problem of efficient representation of scenes captured by distributed omnidirectional vision sensors. We propose a novel geometric model to describe the correlation between different views of a 3-D scene. We first approximate the camera images by sparse expansions over a dictionary of geometric atoms. Since the most important visual features are likely to be equivalently dominant in images from multiple cameras, we model the correlation between corresponding features in different views by local geometric transforms. For the particular case of omnidirectional images, we define the multiview transforms between corresponding features based on shape and epipolar geometry constraints. We apply this geometric framework in the design of a distributed coding scheme with side information, which builds an efficient representation of the scene without communication between cameras. The Wyner-Ziv encoder partitions the dictionary into cosets of dissimilar atoms with respect to shape and position in the image. The joint decoder then determines pairwise correspondences between atoms in the reference image and atoms in the cosets of the Wyner-Ziv image in order to identify the most likely atoms to decode under epipolar geometry constraints. Experiments demonstrate that the proposed method leads to reliable estimation of the geometric transforms between views. In particular, the distributed coding scheme offers similar rate-distortion performance as joint encoding at low bit rate and outperforms methods based on independent decoding of the different images.     

Combining polar harmonic transforms and 2D compound chaotic map for distinguishable and robust color image zero-watermarking algorithm

Although zero-watermarking can provide an effective and distortion-free scheme for image copyright protection, its robustness and discriminability do not meet expectations in existing methods. Some cannot resist effectively geometric attacks, others do not consider the discriminability and equalization. For that reason, this paper proposes a robust and distinguishable color image zero-watermarking algorithm based on polar harmonic transforms (PHTs) and compound chaotic map. In the proposed algorithm, firstly three PHTs moments of an image are computed simultaneously and accurate moments are selected for the robustness. Then, content-based binary feature sequence is acquired by judging the relation between magnitudes of adjacent moments for the discriminability. Finally, compound chaotic map is employed to encrypt copyright logo for ensuring security and scramble binary feature sequence for improving the equalization. Experimental results show that the proposed zero-watermarking algorithm has good equalization and discriminability, and an advantage in robustness compared with other zero-watermarking and traditional watermarking.     

基于级联变换的光学和SAR图像配准算法

针对光学和SAR(Synthetic Aperture Radar)图像配准中存在明显辐射和几何差异的问题,提出了一种基于级联变换的多源遥感图像配准方法.首先,利用灰度变换提取光学和SAR图像间的稳定结构特征,去除辐射差异性;然后,提出一种新的加权对数极坐标变换算法,解决图像间全局几何差异性,保证算法的尺度和旋转不变性,并初步得到整体的平移量;最后,通过局部几何变换,得到一系列的匹配点对,构建薄板样条模型,实现图像的精确配准.实验验证了算法去除辐射差异性和获得全局几何变换参数的能力,与传统的多源图像配准算法相比,基于级联变换的配准算法鲁棒性好,配准精度高.     

一种基于可视密码的轮廓小波图像零水印方案

为了实现数字图像的版权保护,提出了一种基于可视密码的零水印方案.该方案首先实现了一种轮廓小波变换(CWT)的多尺度几何分析方法,然后通过在变换域能量最高的中频子带适当选取系数,结合预定义的可视密码码书,将二值水印图像藏匿于两个分享中,从而构造出零水印信号.实验结果表明,该方案不仅能在不改变原始图像的情况下实现版权保护,而且鲁棒性强,能抵抗JPEG压缩、剪切、加噪、锐化及旋转等图像处理攻击.     

基于提升框架的整数小波变换

提升框架可以从一个新的角度来构造小波滤波器,它的核心是确定预测算子和更新算子。该文 引进了多项式局部拟合方法来求取预测算子和更新算子,对每步提升下取整,就实现了整数小波变换。仿真结果表明,该方法应用于二维数字图像,在一定失真的前提下,具有较高的压缩比,而且小波系数与尺度系数都是整数,不需要量化步骤。因此,它对于整数数据压缩具有重要的意义。     

随机信号Haar小波包变换的性能研究

本文研究了Ｈａａｒ小波包库内各种正交基对应的正交变换用于对随机数字信号进行处理的问题，提出了一种小波包基的编码方案，并且从方差分布、均方误差、率失真函数的角度对各种Ｈａａｒ小波包基对就的正交变换在数据压缩、广义维纳滤波和变换编三中的性能进行比较，总结了其规律。     

Fragile watermarking using finite field trigonometrical transforms

Fragile digital watermarking has been applied for authentication and alteration detection in images. Utilizing the cosine and Hartley transforms over finite fields, a new transform domain fragile watermarking scheme is introduced. A watermark is embedded into a host image via a blockwise application of two-dimensional finite field cosine or Hartley transforms. Additionally, the considered finite field transforms are adjusted to be number theoretic transforms, appropriate for error-free calculation. The employed technique can provide invisible fragile watermarking for authentication systems with tamper location capability. It is shown that the choice of the finite field characteristic is pivotal to obtain perceptually invisible watermarked images. It is also shown that the generated watermarked images can be used as publicly available signature data for authentication purposes.     

一种基于离散余弦变换与奇异值分解的数字图像水印算法

结合奇异值分解（SVD）和离散余弦变换（OCT）的特点,提出了一种基于离散余弦交换与奇异值分解的数字图像水印算法.该算法能够很好地解决透明性和鲁棒性之间的矛盾.算法中采用经过置乱变换的灰度图作为水印,不仅增加了嵌入的信息量,而且提高了水印的安全性.实验结果表明,该算法不仅具有较好的透明性,而且对常见攻击如：叠加噪声、JPEG压缩、滤波以及几何攻击等具有较好的鲁棒性.     

Reconstruction of lost depth data in multiview video-plus-depth communications using geometric transforms

This paper addresses depth data recovery in multiview video-plus-depth communications affected by transmission errors and/or packet loss. The novel aspects of the proposed method rely on the use of geometric transforms and warping vectors, capable of capturing complex motion and view-dependent deformations, which are not efficiently handled by traditional motion and/or disparity compensation methods. By exploiting the geometric nature of depth information, a region matching approach combined with depth contour reconstruction is devised to achieve accurate interpolation of arbitrary shapes within lost regions of depth maps. The simulation results show that, for different packet loss rates, up to 20%, the depth maps recovered by the proposed method produce virtual views with better quality than existing methods based on motion information and spatial interpolation. An average PSNR gain of 1.48 dB is obtained in virtual views synthesised from depth maps using the proposed method.     

Robust image watermarking using non-regular wavelets

An approach to watermarking digital images using non-regular wavelets is advanced. Non-regular transforms spread the energy in the transform domain. The proposed method leads at the same time to increased image quality and increased robustness with respect to lossy compression. The approach provides robust watermarking by suitably creating watermarked messages that have energy compaction and frequency spreading. Our experimental results show that the application of non-regular wavelets, instead of regular ones, can furnish a superior robust watermarking scheme. The generated watermarked data is more immune against non-intentional JPEG and JPEG2000 attacks.