基于二元纯位相滤波器水印的图像篡改定位

二元纯位相滤波器（BPOF）数字图像水印算法将图像离散Fourier变换的BPOF作为水印嵌入到其相应幅值的某个位平面中,较好地实现了图像自认证。研究了利用BPOF水印实现图像篡改定位。其基本原理是将图像划分为互不重叠的分块,通过在各分块中独立嵌入和检测水印,实现图像篡改检测和定位。着重讨论了以不同大小对于图像分块和以不同幅值位平面嵌入水印时,所嵌入水印的不可感知性、检测性能、图像篡改定位能力以及抗JPEG压缩性能。得出了图像分块大小、嵌入水印的幅值位平面及水印检测阈值等参数的选取策略。实验结果证明了BPOF水印可以很好地应用于图像篡改定位。     

基于多位平面嵌入的二元纯位相滤波器水印

二元纯位相滤波器（BPOF）数字水印是一种用于图像真实性认证的半脆弱水印技术。它由图像离散Fourier变换（DFT）的幅值和相位分别得到幅值位平面和BPOF,并将BPOF作为水印嵌入到幅值位平面中。本文〖BP）〗在简要分析基于单一幅值位平面嵌入BPOF水印的基础上,讨论了使用多个幅值位平面嵌入水印并进行了性能分析。通过仿真实验得到了优化方案：以多个幅值位平面嵌入水印,而从其中的最高位平面中提取水印可以明显提高水印性能。     

采用量化嵌入的二元纯位相滤波器图像水印

二元纯位相滤波器数字图像水印算法将图像离散Fourier变换的相位信息作为水印嵌入到其相应的幅值中,较好地实现了图像自认证。研究了通过量化幅值实现水印嵌入,讨论了根据嵌入水印的各幅值系数所处的频率位置调整量化步长,以及在低频域量化嵌入水印。理论分析和实验结果表明,通过量化幅值嵌入水印,可有效改进算法的灵活性、安全性、水印不可感知性和检测有效性,并且在一定程度上提高了抗JPEG压缩性能。     

一种新的自适应音频水印算法

提出了一种基于小波变换的自适应音频水印算法,把一幅二值图像作为水印信息自适应地嵌入音频信号中.仿真实验表明嵌入的水印具有良好的鲁棒性和透明性.     

基于人类视觉系统的小波域数字水印算法

分析了一种小波域数字水印算法，利用人类视觉模型对算法进行了改进。选取一幅有实际意义的二值图像作为水印，在对原始图像进行多级小波分解后，通过修改中频系数来进行水印嵌入。实验证明嵌入水印后的图像具有更好的隐蔽性，并且对JPEG压缩、图像添加高斯噪声、中值滤波等图像处理操作具有很强的鲁棒性。     

基于平衡多小波的改进的盲水印算法

利用图像经过CARDBAL平衡多小波变换(BMWT)后,能量汇聚且平均分摊在最低分辨率子图像4个分量上的特点,提出了一种基于BMWT和DCT的改进的盲水印算法.在彩色图像的饱和度分量上嵌入一幅二值水印图像,水印嵌入前进行Arnold置乱和混沌加密预处理,保证了算法的安全性.实验结果表明,改进后的算法具有良好的鲁棒性,而且在抵抗JPEG压缩性能方面有明显的提高.     

一种基于DWT和HVS的图像版权保护研究

提出一种基于离散小波变换(DWT)的数字水印进行图像版权保护的新方法.将一幅有意义的二值图像作为水印来隐藏,先将水印图像使用推广Arnold的变换进行置乱后和图像同时进行多尺度分解,然后将分解后的水印系数根据人类视觉系统(HVS)特性自适应地嵌入到具有相同尺寸的低中频系数中,重构得到水印图像.实验结果表明,该算法具有较好的不可见性、鲁棒性和安全性.     

一种感兴趣区域二维水印算法的实现

针对图像中用户选定的感兴趣区域ROI(Regions of interest)的保护,提出形状自适应离散小波变换SA-DWT(Shape Adaptive DWT)是实现感兴趣区域二维水印算法的有效工具.水印图像(一幅灰度图像)经压缩后生成可以嵌入的水印序列,同时SA-DWT变换作用于ROI区域,通过选择变换系数的嵌入位置和嵌入准则实现水印信息的嵌入;最后提取水印信号,通过重构恢复水印图像.攻击实验表明该算法可以抵抗常见的图像攻击手段,ROI区域得到了有效保护.     

一种基于视觉模型的小波域图像盲水印算法

本文提出了一种基于混沌置乱和JND阈值的小波域图像盲水印算法.依据人眼的视觉特性,对宿主图像进行离散小波变换,在小波域子带LH2、HL2幅值较大的系数以及LL2幅值较小的系数中嵌入水印,水印的嵌入采用量化调制的方式,并取JND阈值作为量化间隔,使水印实现盲提取.实验结果表明,在一定不可见性的情况下,此算法对一些常见的水印攻击有较好的鲁棒性.     

基于小波变换和纹理特征的水印算法的研究

目前基于小波变换的数字水印算法主要根据频域小波系数的幅值大小确定是否嵌入水印,这种算法的缺点是嵌入水印后的图像的视觉透明度不够好。对目前已有的基于小波变换的数字水印算法进行了研究,在保证嵌入水印的鲁棒性的前提下,也保证嵌入水印后的图像的理想的视觉效果的基础上,提出了一种基于小波变换和图像纹理特征的自适应数字水印算法,该算法利用了图像本身固有的纹理特征来寻找水印的嵌入位置,实验结果表明该方法能较好地降低原始图像视觉失真和经压缩变换后水印图像的失真。     

Visual quality of watermarking for mobile devices

Abstract— In this study, the visual quality of watermarked images, displayed on mobile devices, are evaluated. A watermarking technique in the spatial domain where a watermark is embedded into an image is considered. Three different types of images are considered and for each image five values of watermarking magnitude were tested. The difference in human evaluation of visual quality of a watermarked image, depending upon image properties and the properties of a display was evaluated. In visual assessment tests, images from a mobile phone, PDA, and CRT were used. The visual quality of watermarked image was evaluated by 20 human observers. The results were quantified using statistical testing. The results show that for high‐end displays the magnitude used for watermarking is a critical factor in image quality. In mobile devices the magnitude used for watermarking has little visual effect, especially for technical drawings. Recommendations for proper parameters are given.     

A New Technique for Digital Image Watermarking

In this paper, a new technique is proposed for rotation, scaling and translation （RST） invariant image watermarking based on log-polar mappings （LPM） and phase-only filtering （POF）. The watermark is embedded in the LPM of Fourier magnitude spectrum of the original image, and a small portion of resulting LPM spectrum is used to calculate the watermark positions. This technique avoids computing inverse log-polar mapping （ILPM） to preserve the quality of the watermarked image, and avoids exhaustive search to save computation time and reduce false detection. Experimental results demonstrate that the digital watermarking technique is invariant and robust to rotation, scaling, and translation transformation.     

Adaptive removable visible watermarking technique using dual watermarking for digital color images

This paper proposes a removable visible watermarking system based on a dual watermark technique and blind removal. A visible watermark pattern is embedded in the cosine discrete transform (DCT) domain, taking into consideration the texture and luminance features of the watermark and host images to create a visible watermarked image. To prevent illegal visible watermark removal, the original watermark is embedded in an invisible manner in the visible watermarked image by employing the Quantization Index Modulation-Dither Modulation (QIM-DM) technique, thus ensuring that the original watermark cannot be obtained by malicious attacks. The visible watermark removal process is carried out using only the correct user’s keys, without the need for additional information, such as the original watermark or the original host image, which allows a high-quality image to be obtained; however, if the user’s keys used in the removal process are wrong, the visible watermarked image suffers higher distortion in its content, even in non-visible watermarked regions. The experimental results show that the proposed system outperforms previous related works in terms of blind removal, preservation of the quality of the unmarked recovered image, and higher visual degradation of the content in the recovered image if an illegal removal attempt is performed.     

A low-cost method for reliable ownership identification of medical images using SVM and Lagrange duality

Prevention of false positive and false negative errors is a major challenge for ownership identification and proof of ownership applications using digital image watermarking. Such errors are more critical with sensitive data, such as electronic patient records (EPRs) in medical image watermarking. A false positive error is a watermark detection error, which means that a watermark is detected in a media where there is no watermark. In contrast, a false negative error is an inability of the watermark detector to detect an embedded watermark in a watermarked image. These errors make ownership assessments unreliable, and the incorrect ownership identification of a patient’s record could result in failure of the correct diagnostics and treatments. To address this type of problem, a low-cost technique based on a support vector machine (SVM) and Lagrange duality was proposed to achieve reliable approximations for ownership identification in medical image watermarking without requiring the correction of attacked watermarked images. In this technique, the results of the ownership evaluation are categorized into two independent classes, namely watermark-detected and watermark-not-detected, and higher geometric margins between these classes are associated with higher reliability. To address additional situations with false positive and false negative errors, four different situations, including watermarked, unwatermarked, attacked watermarked and attacked unwatermarked images, were investigated. Experiments were conducted on duo-ISB-bit-plane (BiISB) watermarking using the histogram intersection (HI) technique as a testing platform under JPEG2000 and JPEG image compression attacks and using two groups of images: standard image processing images and X-ray medical images. The experimental investigations revealed that the HI technique guarantees that the rightful owner can be reliably identified even after severe attacks and in the face of context similarities between the watermark and the embedding pixels of the host image.     

Dynamic stochastic resonance-based improved logo extraction in discrete cosine transform domain

In this paper, a dynamic stochastic resonance (DSR) technique is used for blind watermark extraction in discrete cosine transform (DCT) domain. The watermark embedding has been done on mid-band DCT coefficients. DSR has been used to improve the robustness of the extraction algorithm by utilizing the degradation introduced during attacks. DSR is an iterative process that tunes the coefficients of the possibly attacked watermarked image so that the effect of noise is suppressed and hidden information is enhanced. Resilience of this technique has been tested in the presence of various attacks. An adaptive optimization procedure has been adopted for the selection of bistable parameters to achieve maximum correlation coefficient under minimum computational complexity. Using the proposed technique, robust extraction of watermark is obtained without trading-off with visual quality of the watermarked image. When compared with the plain DCT-based technique, DSR-based technique has been found to give remarkable performance.     

一种相移键控数字图像水印算法

根据相移键控原理．提出了一种不可逆DWT域二相相位键控数字图像水印算法．水印信号为二值图像，用不同相位的正弦信号将水印调制后嵌入到数字图像DWT变换系数中；用提取的同频率正弦信号的相位进行水印提取；该方法嵌入的水印具有非常好的安全性，且水印提取不需要原始未加水印的图像．实验结果表明该方法具有很好的不可见性；对JPEG压缩、图像加噪声和图像滤波等常见的图像处理具有极强的鲁棒性．     

A robust associative watermarking technique based on vector quantization

In this paper, the concepts of vector quantization (VQ) and association rules in data mining are employed to propose a robust watermarking technique. Unlike ordinary or traditional watermarking techniques, our approach hides association rules of the watermark, instead of the whole watermark; in other words, the embedded information is the association rules of the watermark. First, VQ encoding is performed on the original image and watermark to generate the index tables, and from which association rules are further mined. Subsequently, by embedding the association rules of the watermark into the association rules of the original image, the purpose for watermarking is accomplished. Finally, VQ decoding technique is applied to reconstruct the watermarked image from the watermarked index table. Experimental results show that our proposed method achieves effective resistance against several image processings such as blurring, sharpening, adding in Gaussian noise, cropping, and JPEG lossy compression. Moreover, the embedding capacity is also significantly increased, so any a complex watermark image is still acceptable in this method.