脊波变换域的一种自适应盲水印算法

为了克服水印鲁棒性和图像视觉质量之间的矛盾,提出了一种脊波变换域自适应盲水印算法.利用脊波变换对图像特征的稀疏表示特性,找出各区域块中视觉重要信息的位置,并将水印嵌入其中.算法中水印嵌入强度依据图像块的内容属性变化,采用了系数可容忍的最大误差作为水印嵌入强度因子,较好地解决了水印鲁棒性和图像视觉质量之间的矛盾.实验结果表明,该算法能够抵抗JPEG压缩、加噪和任意裁剪等攻击,具有很强的鲁棒性,是一种自适应盲水印算法.     

A robust blind watermarking algorithm for depth-image-based rendering 3D images

The protection of 3D contents from illegal distribution has attracted considerable attention and depth-image-based rendering (DIBR) is proved to be a promising technology for 3D image and video displaying. In this paper, we propose a new digital watermarking scheme for DIBR 3D images based on feature regions and ridgelet transform (RT). In this scheme, the center view and the depth map are made available at the content provider side. After selecting the reference points of the center view, we construct the feature regions for watermark embedding. Considering the sparse image representation and directional sensitivity of the RT, the watermark bits are embedded into the amplitudes of the ridgelet coefficients of the most energetic direction. The virtual left and virtual right views are generated from the watermarked center view and the associated depth map at the content consumer side. The watermarked view has good perceptual quality under both the objective and subjective image quality evaluations. The embedded watermark can be detected blindly with low bit error rate (BER) from the watermarked center view, the synthesized left and right views even when the views are distorted and distributed separately. The experimental results demonstrate that the proposed scheme exhibits good performance in terms of robustness against various image processing attacks. Meanwhile, our method can be robust to common DIBR processing, such as depth image variation, baseline distance adjustment and different rendering conditions. Furthermore, compared with other related and state-of-the-art methods, the proposed algorithm shows higher accuracy in watermark extraction.     

基于图像内容的脊波变换域数字水印模型和算法研究

在研究人类视觉(HVS)特性的基础上提出了一种在脊波变换域基于图像内容的数字水印模型。在此模型中,嵌入数字水印的强度归结于数字图像脊波系数的视觉掩盖效应,文中建立了脊波变换域人眼临界可见误差模型。图像的水印检测被归结为Neymann-PeaLrson准则下的统计模型,该模型被用来估算水印检测的最优阈值。作为算例,将临界可见误差模型结合扩展谱技术,提出了一种新颖的图像自适应水印算法,并给出了相应的实验结果。实验表明算法性能大幅度提高。     

基于脊波变换的图像压缩算法

自然图像包括大量的具有明显“直线边缘”的图像,而且边缘表示了图像的主要信息。利用脊波对“直线奇异”的良好刻画,针对具有直线特征的图像,设计基于脊波变换的有损压缩算法。首先对图像进行脊波变换,然后对变换系数进行标量量化、扫描、游程编码和熵编码。仿真实验表明,与基于小波变换的JPEG 2000压缩算法相比,该算法能获得更高的压缩率,同时保持较高的信噪比。     

基于小波和脊波变换的探地雷达信号杂波抑制

针对如何有效去除探地雷达信号的干扰噪声问题,提出了一种基于小波和脊波变换的杂波抑制方法。小波能有效地描述图像的点奇异性,而脊波能有效地描述图像的线奇异性。首先结合小波和脊波的特点,对探地雷达回波信号进行自适应阈值去噪,然后利用脊波的方向敏感性在脊波域去除直达波信号,最终通过处理实际探底雷达数据,验证算法的有效性。     

Hiding digital watermarks using multiresolution wavelet transform

In this paper, an image accreditation technique by embedding digital watermarks in images is proposed. The proposed method for the digital watermarking is based on the wavelet transform. This is unlike most previous work, which used a random number of a sequence of bits as a watermark and where the watermark can only be detected by comparing an experimental threshold value to determine whether a sequence of random signals is the watermark. The proposed approach embeds a watermark with visual recognizable patterns, such as binary, gray, or color image in images by modifying the frequency part of the images. In the proposed approach, an original image is decomposed into wavelet coefficients. Then, multi-energy watermarking scheme based on the qualified significant wavelet tree (QSWT) is used to achieve the robustness of the watermarking. Unlike other watermarking techniques that use a single casting energy, QSWT adopts adaptive casting energy in different resolutions. The performance of the proposed watermarking is robust to a variety of signal distortions, such as JPEG, image cropping, sharpening, median filtering, and incorporating attacks     

一种基于脊波域的盲检数字水印算法

本文提出了一种脊波域的水印嵌入和盲检测算法.脊波变换(ridgelet transform,RT)具有方向敏感性和各向异性的特点,它可获得具有直线特征的图像的稀疏表示.对这类图像进行多尺度脊波变换后,其中最重要的脊波系数代表了图像能量最集中方向的特征,即沿着图像的边缘方向的特征.对一般含有曲线边缘或纹理的图像,可将图像分成小块,将曲线近似作直线处理.然后,对每个小块进行多尺度脊波变换,选择出脊波系数能量大于某个阈值的方向,并在该方向的中频脊波带嵌入水印.实验证明,水印使用该嵌入方法具有很强的鲁棒性和透明性.     

Robust template matching for affine resistant image watermarks

Digital watermarks have been proposed as a method for discouraging illicit copying and distribution of copyrighted material. This paper describes a method for the secure and robust copyright protection of digital images. We present an approach for embedding a digital watermark into an image using the Fourier transform. To this watermark is added a template in the Fourier transform domain to render the method robust against general linear transformations. We detail a new algorithm based on polar maps for the accurate and efficient recovery of the template in an image which has undergone a general affine transformation. We also present results which demonstrate the robustness of the method against some common image processing operations such as compression, rotation, scaling, and aspect ratio changes.     

Robust image watermarking based on multiband wavelets and empirical mode decomposition.

In this paper, we propose a blind image watermarking algorithm based on the multiband wavelet transformation and the empirical mode decomposition. Unlike the watermark algorithms based on the traditional two-band wavelet transform, where the watermark bits are embedded directly on the wavelet coefficients, in the proposed scheme, we embed the watermark bits in the mean trend of some middle-frequency subimages in the wavelet domain. We further select appropriate dilation factor and filters in the multiband wavelet transform to achieve better performance in terms of perceptually invisibility and the robustness of the watermark. The experimental results show that the proposed blind watermarking scheme is robust against JPEG compression, Gaussian noise, salt and pepper noise, median filtering, and ConvFilter attacks. The comparison analysis demonstrate that our scheme has better performance than the watermarking schemes reported recently.     

适用于尺寸为2的幂次方图像的离散ridgelet变换

Ridgelet变换是继小波变换之后提出的一种新的多尺度变换,它能比小波变换更好地表达高维线性奇异性。Finite ridgelet是ridgelet变换的离散实现算法,具有和连续ridgelet变换一样精确的代数意义,并且算法复杂度低。但是finite ridgelet只适用于图像尺寸为PP(P为素数)的图像,这一点限制了它的应用范围。该文将finite ridgelet的算法进行改进,提出了一种可以适用于图像大小为NN ( N=2k, kZ)的离散ridgelet算法。该算法不仅推广了finite ridgelet的适用范围,而且简化了finite ridgelet的算法过程。     

基于Turbo码的DCT域直流分量图像水印算法

文中提出了一种基于Turbo码的DCT变换域直流分量图像水印算法。首先对原始水印信息进行伪随机置乱,接着对置乱的水印进行Turbo编码并进行BPSK调制,生成待嵌入的水印信息。在充分考虑人眼视觉特性的基础上,分别采用两种方式将水印嵌入到DCT变换系数的De分量中,并进行性能比较。丈中对算法在多种常见的攻击如JPEG压缩、噪声、剪切、滤波下进行了仿真。实验结果表明,利用该算法实现的水印具有良好的不可见性和鲁棒性。特别是非自适应加性嵌入方式对JPEG压缩攻击具有很强的鲁棒性。     

Using Curvelet transform for watermarking based on amplitude modulation

In this paper, we propose a precise and robust watermarking scheme based on the technique called amplitude modulation. A watermark is embedded in a color image by modifying the pixel values in the blue channel. At the receiver, the watermark bits are retrieved using a prediction system, by a linear combination of nearby pixel values around the embedded pixels, and without having the original image. Because amplitude modulation is a spatial-domain watermarking method, it may not be robust enough, i.e., incapable of exact watermark retrieval. In order to enhance the bit retrieval, we apply a Gaussian mask to equalize the luminance intensity; we employ the pixel value replacing technique to enhance the prediction performance, and we use two additional bits as a geometrical reference. In addition, we demonstrate that choosing an improper location (like singularities) for watermarking will lead the prediction system to malfunction. In order to increase the robustness, we propose using the Curvelet transform to detect singularities such as lines and curves and to prevent the system from using these locations in an image for embedding the watermark bits. The experimental results indicate that our proposed method has a better performance in comparison with two other similar approaches, and in addition, it is robust against various geometrical and nongeometrical attacks as well as having a good imperceptibility.     

基于有限脊波变换的图像内容认证算法

在有限脊波变换(FRIT,finite ridgelet transform)域,提出了一种用于图像内容认证的半易损数字水印算法。提取图像在FRIT时产生的均值信息作为图像内容特征,并由它生成认证水印。利用Bayesian最小风险函数估计选择FRIT系数,把认证水印嵌入这些系数。实验结果表明,此算法简便高效,能很好地区分图像内容的恶意篡改和偶然修改,并能确切指出篡改的位置。     

Robust image watermarking using a chirp detection-based technique

A new robust image watermarking algorithm that embeds multiple watermark bits in the host image is proposed. Linear chirps are embedded as watermark messages, where the slopes of the chirp on the time-frequency (TF) plane represent watermark messages, such that each slope corresponds to a unique message. The Hough-Radon transform (HRT) is a widely used tool to detect directional elements that satisfy a parametric constraint in images. Since linear chirps are localised as a straight line in the TF plane, the HRT is used to detect the watermark messages at the receiver. The HRT acts as an error correcting scheme and robustly estimates the slope of the chirps in the presence of any attacks. It is found that the HRT based detector is able to detect the watermark message accurately when the bit error rate is less than 20%. The robustness of the proposed scheme has been evaluated using the checkmark benchmark attacks.     

A robust blind watermarking method using quantization of distance between wavelet coefficients

In this paper, we propose a robust blind watermarking algorithm based on quantization of distance among wavelet coefficients for copyright protection. We divide wavelet coefficients into some blocks and obtain the first, second, and third maximum coefficients in each block. Then, we quantize the first and second maximum coefficients according to binary watermark bits. Using the block-based watermarking, we can extract the watermark without using the original image or watermark. The algorithm as a watermarking system has appropriate performance due to imperceptibility. In addition, experimental results also show that the proposed method is quite robust under either non-geometry or geometry attacks.     

一种基于JPEG压缩的半脆弱水印算法

本文分析了JPEG压缩中的DCT变换和量化过程，根据量化的特性提出了一种半脆弱水印方案，并将水印信息调制为纠错码嵌入JPEG压缩过程的量化系数中，实验证明，此水印方案鲁棒性较强，虚警率低，能较好的检测图像是否被篡改并对篡改定位。     

A robust color image watermarking algorithm against rotation attacks

A robust digital watermarking algorithm is proposed based on quaternion wavelet transform (QWT) and discrete cosine transform (DCT) for copyright protection of color images. The luminance component Y of a host color image in YIQ space is decomposed by QWT, and then the coefficients of four low-frequency subbands are transformed by DCT. An original binary watermark scrambled by Arnold map and iterated sine chaotic system is embedded into the mid-frequency DCT coefficients of the subbands. In order to improve the performance of the proposed algorithm against rotation attacks, a rotation detection scheme is implemented before watermark extracting. The experimental results demonstrate that the proposed watermarking scheme shows strong robustness not only against common image processing attacks but also against arbitrary rotation attacks.     

一种基于Ridgelet变换的遥感图像融合方法

Ridgelet变换是继经典的小波变换之后提出来的一种新型图像多尺度几何分析工具.针对不同波段的远程遥感图像提出了一种基于新型正交Ridgelet变换的遥感图像融合方法.该算法基于新型的可逆离散脊波多尺度变换,通过客观评估融合性能说明该方法优于其他三种典型融合方法,尤其是优于各种基于小波变换的图像融合方法,仿真实验证明该方法融合效果良好.     

基于脊波变换的图像篡改检验算法

针对数字图像篡改一种最经常使用的复制-粘 贴篡改手段,提出了一种基于脊波变换的 图像篡改检测取证方法。算法利用了脊波变换是Radon变换切片上应用小波变换这种 特性,实现了 复制-粘贴篡改的鲁棒识别。针对十一大类图像的仿真实验结果表明,算法对于旋转变换、 JPEG压缩和噪 声添加都具有良好的鲁棒性,对于压缩新标准JPEG2000也表现出了较 好的鲁棒性。     

基于自适应半脆弱水印的图像篡改检测方案

为保护数字图像版权和检测恶意篡改,实现高精度篡改定位,在充分挖掘图像特性的基础上,设计一种基于自适应半脆弱水印技术的图像篡改检测算法。算法根据感知特性将水印自适应嵌入到图像LSBs中,利用多数原则恢复水印信号,结合数学形态学滤波进行篡改检测与定位。仿真实验证实了该方案的有效性,在抵抗通常的内容保持攻击操作的同时,能实现精准篡改检测与定位。