A feature-based robust digital image watermarking scheme using bandelet transform

Desynchronization attacks are among the most difficult attacks to resist, for it can desynchronize the location of the watermark and hence cause incorrect watermark detection. The design of an image watermarking scheme that is robust against desynchronization attacks is challenging. Based on a multi-scale SIFT (scale invariant feature transform) detector and Bandelet transform theory, we propose a new content based image watermarking algorithm with good visual quality and reasonable resistance toward desynchronization attacks. Firstly, the stable image feature points are extracted from the original host by using the multi-scale SIFT detector, and the local feature regions (LFRs) are constructed adaptively according to the feature scale theory. The Bandelet transform is then performed on the LFRs. Finally, the digital watermark is embedded into the LFRs by modifying the significant Bandelet coefficients. By binding the watermark with the geometrically invariant image features, the watermark detection can be done without synchronization error. Experimental results show that the proposed image watermarking is not only invisible and robust against common signal processing such as sharpening, noise adding, JPEG compression, etc., but also robust against the desynchronization attacks such as rotation, translation, scaling, row or column removal, cropping, etc.     

A robust watermarking algorithm based on salient image features

A feature-based robust watermarking algorithm against geometric attacks is proposed in this paper. It is well-known that geometric attacks such as rotation, scaling, and translation on a watermarked image will destroy the synchronization between the processes of watermark embedding and detection. In other words, the locations for embedding the watermark are lost due to geometric attacks, which results in the failure of watermark detection. Since salient features in an image are relatively stable under geometric attacks, they may serve as reference points to synchronize the embedding and detection processes and the detection rate of the watermark could be increased significantly. Another problem for feature-based watermarking is that the repeatability of feature detection tends to be low; that is, the features detected during the embedding process may not be detected again during the detection process. To overcome such a problem, a novel feature enhancement technique is developed to increase the repeatability rate of feature detection, in which image moments are used to achieve geometric invariance between the embedding and detection processes. Experimental results demonstrate that the proposed watermarking algorithm is able to survive various geometric attacks and common image processing operations. And the visual quality of the watermarked image is well preserved as well.     

尺度不变特征与几何特征融合的人耳识别方法

要提高人耳的识别率,关键是特征的提取与表达.尺度不变特征变换(SIFT)技术是局部点特征提取算法,在尺度空间寻找极值点,提取对图像的尺度和旋转变化具有不变性,对光照变化和图像变形具有较强的适应性的特征向量.尝试用SIFT技术来提取外耳图像的结构特征点以形成稳定的特征描述子,为了克服一幅图像中有多个局部描述子相似的问题,在SIFT特征描述子中融入一个耳廓几何特征.最后采用特征向量的欧氏距离作为两幅图像相似性度量标准进行人耳识别.在耳图像库七进行实验.结果表明,该方法不仅可以有效地提取人耳特征,通过少量特征可获得较高的识别率,而且对耳图像刚体变化具有较强的稳健性.     

基于SIFT图像特征区域的全息水印技术

为了增强水印的不可见性和鲁棒性,提出了一种基于图像特征区域的水印算法。首先利用SIFT(Scale Invariant Feature Transform)算法从载体图像蓝色B通道中提取图像特征点来进行优化和筛选,根据优化后的稳定特征点及其特征尺度确定图像的特征区域,再结合全息技术,对原始水印图像进行双随机相位加密,生成加密全息水印;然后对特征区域进行离散余弦变换(DCT);最后在其中频区域嵌入加密全息水印。在提取水印时无须借助原始图像,是盲水印技术。实验结果表明:该算法重建的水印图像与原始水印图像的NC值高达0.95;水印的嵌入对图像质量影响很小,PSNR值高达55.97,能够抵抗常规信号攻击及缩放、剪切、平移等几何攻击。     

基于SIFT特征区域的抗几何攻击图像水印算法

提出了一种基于局部特征区域的抗几何攻击图像水印算法.首先利用尺度不变特征变换在载体图像的尺度空间上提取特征点并形成特征区域,该区域具有缩放、平移不变性;然后通过主方向归一化,使这些区域具有旋转不变性;最后将水印信息重复嵌入到多个不重叠的局部特征区域的DFT中频系数中.仿真结果表明,该算法在获得较好的不可见性的同时,对几何攻击和常规信号处理均具有良好的鲁棒性.     

自嵌入双功能图像水印算法

利用自嵌入技术提出一种同时实现版权保护和内容认证的双功能图像水印算法.在嵌入端,首先将原始图像划分成互不重叠的子块,将各子块每个像素的最低m位置0,然后将最低m位置0后的子块进行奇异值分解,通过提取奇异值范数的最高位奇偶性产生原始鲁棒特征水印,然后再将原始鲁棒特征水印嵌入各子块每个像素的最低m位得到含水印图像.检测端从攻击的含水印图像提取鲁棒特征水印的过程与嵌入端产生原始鲁棒特征水印的过程类似,并且通过计算提取的鲁棒特征水印与原始鲁棒特征水印之间的归一化相关度进行版权鉴别,通过判断提取的鲁棒特征水印与攻击图像各子块每个像素的最低m位的一致性实现篡改检测进行内容认证.理论分析和实验结果都表明算法具有非常好的不可见性.实验结果还表明,算法不仅在抵抗添加噪音、剪切、JPEG压缩、平滑、重采样和几何攻击如随机删除行、向右偏移列、向下偏移行表现出很强的鲁棒性,而且能够精确定位出篡改位置和区分篡改类型.因此,算法具有版权保护和内容认证双重功能.     

Rotation, scaling, and translation invariant local watermarking technique with Krawtchouk moments

A rotation, scaling, and translation invariant local watermarking is proposed with one or two Krawtchouk moment(s) of the original to estimate the geometric distortion parameters including rotation angle, scaling factor, and translation parameter. Krawtchouk moments can be used as private key of watermark extractor.Watermark is inserted into perceptually significant Krawtchouk moments of original, and watermark based on Krawtchouk moments is local. Independent component analysis (ICA) is utilized to extract watermark blindly. Experimental results show that this method has a good robustness against distortions preformed by watermark benchmark Stirmark.     

A novel blind digital watermarking algorithm for embedding color image into color image

A robust and blind watermarking technique for dual color images is proposed in this paper. According to the energy concentrating feature of DCT, the two-level DCT is introduced and used to embed color watermark image into color host image, which is completely different with the traditional DCT. For reducing the redundancy of watermark information, the original color watermark image is compressed by the proposed compression method. After two-level DCT, nine AC coefficients in different positions of each sub-block are selected and quantified to embed watermark information. Moreover, only the extraction rules are used to extract watermark from the watermarked image without resorting to the original host image or watermark image. Experimental results show that the proposed watermarking algorithm can effectively improve the quality of the watermarked image and the robustness of the embedded watermark against various attacks.     

结合Harris与SIFT算子的图像快速配准算法

本文提出了一种结合Harris与SIFT算子的快速图像配准方法。首先,对Harris算法进行两方面的改进:一是构建高斯尺度空间,提取具有尺度不变性的角点特征;二是采用Forsnter算子对提取的角点精定位,提高配准精度。然后,利用SIFT算子的特征描述方法描述提取到的特征点,通过随机kd树算法对两幅影像的特征点进行匹配。最后采用RANSAC算法对匹配点对进行提纯,并通过最小二乘法估计两幅影像间的空间变换单应矩阵,完成图像配准。实验结果表明:本文方法在基本保持配准精度的同时,在配准过程的时间消耗上比标准SIFT算法减少了64%。     

一种基于特征不变描述的图像无缝拼接算法

针对尺度变化不明显场景的拼接,提出一种基于特征不变描述的图像无缝拼接算法.利用Harris特征检测算子进行特征点提取,在此基础上对提取出的特征点采用SIFT描述子进行处理,使其具备旋转不变性,然后利用k-d树算法进行遍历搜索定位,并用RANSAC算法进行图像间单应性变换矩阵计算,最后利用加权平均的融合方法进行图像无缝平滑,得到无缝拼接图像.实验结果表明:该算法在图像任意角度旋转的情况下,能有效地实现图像无缝拼接,并具有较强的鲁棒性.     

基于双混沌置乱和扩频调制的彩色图像盲水印算法

提出了一种新的适应彩色图像的盲水印算法,先对宿主图像的绿色分量以8×8像素分块进行离散余弦变换(DCT)变换,用logistic映射生成两个混沌序列,然后用混沌序列置乱加密二值水印图像,并用两个互不相关的伪随机序列扩频调制水印,最后将调制好的水印嵌入到DCT变换域的中频子带系数上,进行分块DCT反变换得到水印化图像.提取水印时,通过比较两个伪随机序列和水印化图像的相关性大小来提取水印,不需要原始图像的参与,为盲提取水印算法.实验结果证明本文算法能有效地抵抗JPEG压缩、加噪、剪切等常见攻击,绿色分量嵌入水印比红色和蓝色分量嵌入水印能更好地抵抗JPEG压缩的攻击.     

A novel three-dimensional digital watermarking scheme basing on integral imaging

A novel integral imaging-based three-dimensional (3D) digital watermarking scheme is presented. In the proposed method, an elemental image array (EIA) obtained by recording the rays coming from a 3D object through a pinhole array in the integral imaging system is employed as a new 3D watermark. The EIA is composed of a number of small elemental images having their own perspectives of a 3D object, and from this recorded EIA various depth-dependent 3D object images can be reconstructed by using the computational integral imaging reconstruction (CIIR) technique. This 3D property of the EIA watermark can make a robust reconstruction of the watermark image available even though there are some data losses in the embedded watermark by attacks. To show the robustness of the proposed scheme against attacks, some experiments are carried out and the results are discussed.     

一种新的红外成像末制导目标跟踪方法

为了稳定跟踪导弹末制导阶段的红外目标,提出了一种基于尺度不变特征变换的红外目标跟踪算法.尺度不变性特征变换所提取的图像纹理特征具有尺度和旋转不变性,跟踪算法分别提取目标模板和待跟踪图像的尺度不变特征变换特征.根据最小欧氏距离准则提取目标模板与待跟踪图像间相匹配的尺度不变特征变换特征点对,利用该特征点对拟合反映两图像间映射关系的仿射模型,并据此估计目标中心位置及调整目标模板尺寸.仿真结果表明,跟踪算法能够较好地实现在导弹末制导阶段对红外地面杂波背景下目标的稳定跟踪,其跟踪准确度和稳定度优于传统方法.
关键词:末制导跟踪|尺度不变性特征变换|特征匹配|仿射模型     

The high precision positioning algorithm of circular landmark center in visual measurement

For vision measurement in the center circle landmark location problem, an improved center of the ellipse based on Zernike moments sub-pixel positioning algorithm was proposed. First, using Sobel operator edge of the image pixel level positioning and then use the constructed Zernike moments to solve the model, combined with Zernike orthogonal polynomials and completeness and plural moment magnitude rotational invariance calculated edge sub-pixel position; followed by analysis of the principle deviation generated by the moments template and ideals model, a correction formula was proposed to compensate and improved edge criterion used to image sub-pixel edge positioning; finally, using the least-squares ellipse fitting algorithm fitting circle center, reverse edge point, filtered residuals larger point, and then precise positioning of the ellipse center. The experimental results show that this method has good stability and high positioning accuracy can be efficiently used in many applications.     

基于Zernike正交矩的亚像素图像线宽测量算法

针对图像内的细窄线宽,提出了一种基于Zernike正交矩的亚像素图像线宽检测算法。该算法具有明确的几何模型,通过计算图像的2阶和4阶Zernike正交矩,推导出了亚像素线宽表达式。根据数字图像的离散性,给出了计算正交矩所需的模板系数,并分析了由离散性造成的原理误差。将所提出的亚像素线宽检测技术应用于安瓿内异物粒径的标定实验,结果表明:该算法可有效地测量弱小目标在图像中的亚像素线宽值,从而得到了异物粒径大小与亚像素线宽之间的标定曲线。     

A blind color image watermarking based on DC component in the spatial domain

Color image watermarking has become essential and important copyright protection or authentication scheme. It is noted that most of the existing color image watermarking algorithms are performed only in the single domain (spatial domain or frequency domain), and not to integrate these merits of the different domains. By utilizing the generating principle and distribution feature of the direct current (DC) coefficient, a novel blind watermarking algorithm is proposed for color host images in this paper. Firstly, the Y luminance of host image is divided into 8 × 8 sub-blocks and the DC coefficients of each block are directly calculated in the spatial domain without DCT transform. Secondly, according to the watermark information and the quantization step, the DC coefficients are calculated and their increments are further utilized to modify directly the values of all pixels in the spatial domain instead of the DCT domain to embed watermark. When watermark extraction, only the watermarked image and the quantization step are needed in the spatial domain. Experimental results show that the proposed method not only can resist both traditional signal processing attacks and geometric attacks, but also has more efficient in computational complexity. Comparisons also demonstrate the advantages of the method.