基于支持向量回归的Contourlet域盲水印算法

为进一步提高基于支持向量机(SVM,support vector machine)水印算法的性能,提出了基于支持向量回归(SVR,support vector regression)的Contourlet域盲水印算法。首先对宿主图像进行Contourlet分解,然后利用SVM建立图像尺度内的局部相关性模型,根据模型的预测结果自适应地嵌入水印。实验结果表明,所提出的算法不仅具有较好的不可感知性,而且对叠加噪声、JPEG压缩、锐化、平滑滤波和对比度增强等常规图像信号处理以及旋转、剪切等几何攻击均具有较好的鲁棒性,其性能明显优于基于SVM的空间域和小波域的水印算法。     

基于复Contourlet域的支持向量机和Krawtchouk矩的双水印算法

为了进一步提高基于支持向量机(SVM)水印算法的 鲁棒性,提出了一种 基于复Contourlet域的SVM和Krawtchouk矩的双水印算法。首先从RGB宿主 图像中提取B 分量和G分量,并且充分利用Krawtchouk矩不变量的平移、旋转、缩放不变性 和Krawtchouk矩良好 的局部重构特性,计算B分量图像的Krawtchouk低阶矩不变量 ,由此构造鲁棒水印;然后对G分量图 像进行两级复Contourlet分解,在其低频分量中,利用SVM建立图像尺度内的 局部相关性训练模型, 并根据预测结果自适应地实现数字水印图像的嵌入和提取。大量实验结果表明,本文算法不 仅具有较好的 不可感知性,而且对中值滤波、加性噪声和JPEG压缩之类的常规图像处理,以及缩放、旋转 和剪切等几 何攻击,均具有较好的鲁棒性能,其性能优于基于小波域的SVM和基于Contourlet域的SVM水 印算法。     

基于能量估计和视觉模型的数字水印算法

本文将数字水印能量估计方法拓展到分块离散余弦变换 (DCT)域,并且提出了一种基于分块DCT的数字水印算法,将能量估计方法应用于该算法中。该算法利用了人眼视觉系统 (HVS)模型,将水印信息嵌入到DCT系数的低、中频域,试图达到不可感知性和鲁棒性的最佳折衷,进而提出了一种灵活的重复嵌入策略及相应的检测算法。实验结果表明,该算法在较大的信息嵌入量情况下仍然具有较好的不可感知性和对多种攻击的鲁棒性。     

一种基于特征的自适应水印算法

基于图像多尺度空间理论和扩频机制以及视觉感知模型的特性,给出一种基于特征的数字图像水印算法。算法采用尺度不变特征变换算子提取图像的局部不变特征区域,根据信噪比特点自适应选取水印嵌入强度因子,将一幅二值水印图像嵌入到原始图像中,实现了数字水印的不可感知性和鲁棒性。仿真结果表明,该算法对添加噪声、压缩、旋转等常见的图像处理攻击具有较强的鲁棒性。     

DCT域下采样视频水印技术

根据DCT域Watson模型提出了一种抵抗下采样攻击的不可感知水印模型.用DCT域准卷积下采样方法得到图像的下采样版本,利用亮度特征和图像感知失真限制自适应确定被嵌入水印序列的区域、长度和强度,以使上采样水印图像具有良好的视觉效果和鲁棒性.实验结果表明该算法对噪声干扰及视频下采样具有较好的鲁棒性,而且不使用原始图像,就可进行水印的相关检测.     

基于子采样方法的DCT域盲水印技术

提出了一种增强水印鲁棒性的盲水印算法.算法在DCT(离散余弦变换)变换域,采用子采样的方法,选择嵌入水印的位置;以视觉感知模型调节嵌入水印的强度.算法的提取不需要原始图像,实现了盲提取.实验结果表明,算法不仅具有较好的不可见性,水印信息在噪声干扰、滤波、图像压缩等攻击下具有较好的鲁棒性.     

DCT域音频水印:水印算法和不可感知性测度

针对音频信号,提出了一种水印算法,该算法利用DCT频谱中的DC直流系数数据正负性不易改变的特性来嵌入水印信息,通过实验结果说明该水印算法可以在鲁棒性与不可感知性之间达到平衡.另外,提出了一种结合心理声学模型的客观评价含水印信号失真度的方法,通过实验结果和理论上的分析都说明这种不可感知性的测度可以体现人类听觉的主观特性,是一种比较合适的客观评价方法.     

一种基于听觉掩蔽效应的音频数字水印算法

基于听觉掩蔽效应,提出了一种在WAV格式音频信号中嵌入WAV格式音频水印的离散小波变换域高效水印算法,用Matlab7．0编程进行了水印的嵌入、提取及防盗版性能研究。仿真实验表明,该算法嵌入的音频水印具有较好的不可感知性和较强的抗版权篡夺能力,并且对诸如重新采样、低通滤波和叠加噪声等攻击具有较好的鲁棒性。     

基于范数的DWT域鲁棒音频水印算法

在音频信号中添加水印后能保持不可感知性,满足一定的水印容量且同时具有较好的鲁棒性,是数字音频水印研究领域中的一项重要课题.针对这一问题,提出一种基于范数的离散小波变换(Discrete Wavelet Transformation,DWT)域鲁棒音频水印算法.首先对音频信号分帧,然后对每帧信号进行6级DWT分解,并选取低频系数构造成两个向量,分别计算向量范数,通过量化向量范数实现嵌入水印的目的,保证水印的鲁棒性.此外,利用Arnold变换和Logistic混沌序列对水印进行置乱和加密,提高水印的安全性.仿真实验结果表明,所提算法的水印安全性高,能在平均信噪比为30.01 dB,水印容量为43.07 b·s-1的情况下,对添加噪声、低通滤波、重采样、重量化以及MP3压缩等各种常见的音频信号处理攻击具有良好的鲁棒性.     

用于版权管理的数字音频水印算法

该文提出了一种用于多媒体资料版权管理的自同步音频盲水印算法。由于版权应用需要通过解码结果得到素材的使用情况,对解码结果时间精度有一定要求,同时对鲁棒性和不可感知性要求也较高。针对之前算法存在鲁棒性不够,时间精度低的问题。该文提出的算法利用扩频的方法和音频信号的短时相关的特性提高嵌入水印的鲁棒性的同时,通过心理声学模型的应用改善算法的不可感知性。算法通过合理设计了水印信息帧结构和同步策略提高了解码结果的时间精度。实验结果表明,该文的方法在具有很高不可感知性的情况下,能够有效地抵抗各种常见的音频编辑操作。     

Watermarking scheme based on support vector machine for colour images

A novel watermarking scheme based on the support vector machine is proposed. The watermark is embedded in the blue channel of a colour image. By applying the embedded extra reference watermark, the support vector machine is trained, and then the watermark can be extracted by the trained support vector machine. Owing to the good generalisation ability of the support vector machine, even when the watermarked image is heavily distorted the watermark can be successfully extracted. Experimental results show good robustness of the proposed scheme.     

A novel image watermarking scheme against desynchronization attacks by SVR revision

In digital image watermarking, the watermark’s vulnerability to desynchronization attacks has long been a difficult problem. On the basis of support vector regression (SVR) theory and local image characteristics, a novel image watermarking scheme against desynchronization attacks by SVR revision is proposed in this paper. First, some pixels are randomly selected and the sum and variance of their neighboring pixels are calculated; second, the sum and variance are regarded as the training features and the pixel values as the training objective; third, the appropriate kernel function is chosen and trained, a SVR training model will be obtained. Finally, the sum and variance of all pixels’ neighboring pixels are selected as input vectors, the actual output can be obtained by using the well-trained SVR, and the digital watermark can be recovered by judging the output vector. Experimental results show that the proposed scheme is invisible and robust against common signals processing such as median filtering, sharpening, noise adding, and JPEG compression, etc., and robust against desynchronization attacks such as rotation, translation, scaling, row or column removal, shearing, local random bend, etc.     

Zero-bit Watermarking resisting geometric attacks based on composite-chaos optimized SVR model

The problem to improve the performance of resisting geometric attacks in digital watermarking is addressed in this paper.Based on the optimized support vector regression(SVR),a zero-bit watermarking algorithm is presented.The proposed algorithm encrypts the watermarking image by using composite chaos with large key space and capacity against prediction,which can strengthen the safety of the proposed algorithm.By using the relationship between Tchebichef moment invariants of detected image and watermarking characteristics,the SVR training model optimized by composite chaos enhances the ability of resisting geometric attacks.Performance analysis and simulations demonstrate that the proposed algorithm herein possesses better security and stronger robustness than some similar methods.     

抵抗几何攻击的数字图像水印

该文实现了一种抵抗几何攻击的数字图像水印方案。水印信号为根据密钥产生的服从正态分布的实数序列,对水印信号作预处理并进行周期化之后在空域将其嵌入数字图像中。检测端不需要原始图像,根据预测水印的自相关函数(ACF)判断水印图像遭受的几何变换攻击并进行逆变换,然后进行水印检测。实验表明该方案对压缩、滤波、剪切等常见的图像处理攻击同样具有很高的鲁棒性。     

新颖的基于小波变换的数字水印方案

随着计算机网络技术与多媒体技术的快速发展，数字产品的版权保护已经成为信息技术领域中最重要的问题之一，提出了一种新颖的基于离散小波变换的数字水印方案，该方案利用改进的Pacthwork算法，将水印嵌入到LL子带中，水印信号在解码过程中无需使用原始图像可快速地重嵌入，该算法利用BCH码来降低误码率，应用所提出的算法，把一个32个字符的水印嵌入到图像中，实现结果表明水印是不可察觉的，经过JPEG有损压缩，低通与中值滤波等图像处理操作后仍是鲁棒的。     

APPLICATION OF NONLINEAR WATERMARK TECHNIQUES IN DIGITAL LIBRARIES

A digital watermark is an invisible mark embedded in a digital image that may be used for a number of different purposes including copyright protection. Due to the urgent need for protecting the copyright of digital products in digital library, digital watermarking has been proposed as a solution to this problem. This letter describes potential situations that nonlinear theory can be used to enhance robustness and security of the watermark in digital library. Some nonlinear watermark techniques have been enumerated. Experimental results show that the proposed scheme is superior to the general watermark scheme both in security and robustness in digital library.     

Grouping strategies for promoting image quality of watermarking on the basis of vector quantization

In this paper, a novel vector quantization (VQ)-based digital image watermarking scheme is proposed which retains high image quality even after embedding. The general scheme of watermarking is to embed a representative digital watermark in the protected image to claim the ownership. The robustness of watermark is important; however, the imperceptibility of embedded images also cannot be ignored. In previous papers, existing greedy technique to group codewords often results in low quality of stego-images. As an improvement to the existing techniques, two new grouping strategies, codebook-sort grouping and bipartite-match grouping are proposed in this paper to improve the quality of stego-images. Moreover, a new VQ encoder, called as shortest-group encoding method is proposed to replace the traditional VQ encoder in the purpose of embedding. Finally, in order to improve the grouping flexibility, two kinds of weights are considered in our approach. Experimental results show that all of the above approaches can improve the quality of stego-images on VQ-based watermarking.     

Self Embedding Watermarking Using Halftoning Technique

This paper proposes a self-embedding watermarking scheme for digital images. It exploits a digital halftoning technique to transform the host image to a halftone image, in which the content features of the host image are well preserved. This halftone image is utilized as an approximate or compressed version of the host image and further adopted as a watermark. Unlike most available self-embedding watermarking techniques, in which watermark embedding, tamper detection and image recovery are block-wise-based, our scheme is a pixel-wise and block-wise composite scheme. That is, the watermark is pixel-wise permuted and embedded in the least-significant-bit plane of the host image, while in tamper detection and image recovery, a block-wise strategy is employed. This pixel-wise and block-wise complementary mechanism can overcome a common disadvantage of previous block-wise-based self-embedding watermarking techniques. Our scheme can be used for tamper detection and alteration location. Moreover, the tampered area can be approximately recovered using the extracted watermark. Experimental results demonstrate the effectiveness of the proposed scheme.     

基于几何矩的抵抗RST攻击的数字图像水印

目前大多数的数字图像水印方案不能有效抵抗几何形变的攻击,这一弱点已成为数字水印技术走上商用的瓶颈。在各种几何形变中,RST(旋转、缩放、平移)是最为常见的攻击方式。该文提出了一种具有普适性的能够抵抗RST攻击的多比特数字图像水印方案,采用的主要措施有:(1)提出一种基于几何矩的图像标准化方案以抵抗几何攻击;(2)采用扩谱方法构造二维CDMA水印信号,实现多比特水印嵌入;(3)根据HVS特性自适应调整水印的嵌入强度,在鲁棒性和不可见性之间达到平衡;(4)利用MAP和相关方法估计和检测水印信号。实验表明该方案对RST具有很高的鲁棒性,对压缩、滤波等常见的图像处理攻击同样具有良好的鲁棒性。