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1.
以图像和文本为掩护的隐蔽通信及其对抗技术 总被引：1，自引：0，他引：1
1IntroductionSince the early1990s,information hiding has be-come a hot topic attracting much attention from re-searchers in various fields including signal processing,cryptography and computer science,developers andsuppliers of multi media contents,and professionalsand other personnel who are concerned with informa-tion security[1].Two major areas are of the most inter-ests:digital watermarking and steganography.The purpose of digital watermarkingis to protect in-tellectual property rights of … 相似文献
2.
In this paper, a set of unified finite-difference time-domain (FDTD) formulae are presented. These formulae are applicable to underwater sound scattering from various objects with a finite acoustic impedance, either with or without shear strains. A major improvement has been made to the FDTD algorithm to remove most of the loop operations. This makes the finite-difference field computation very efficient and, more importantly, suitable for the implementation of distributed parallel computing. Other advantages of the new algorithm include the ease in modeling objects having complicated shapes. Numerical experiment results are presented to show the effectiveness of the proposed method. 相似文献
3.
In this work, image feature vectors are formed for blocks containing sufficient information, which are selected using a singular-value criterion. When the ratio between the first two SVs are below a given threshold, the block is considered informative. A total of 12 features including statistics of brightness, color components and texture measures are used to form intermediate vectors. Principal component analysis is then performed to reduce the dimension to 6 to give the final feature vectors. Relevance of the constructed feature vectors is demonstrated by experiments in which k-means clustering is used to group the vectors hence the blocks. Blocks falling into the same group show similar visual appearances. 相似文献
4.
Daily return series of Dow Jones industrial Average Index(DJIA) and shanghai Conposite Index are inverstigated using spectral analysis methods.The day-of-the-week effect is found in the frequency domain in both stock markets.Time-domain performances of the daily returns are also studied.Although both markets have a clear weekly component in the frequency domain,they show some different behaviors with respect to the day-of -the -week effects. 相似文献
5.
A color-intensity feature extraction method is proposed aimed at supplementing conventional image hashing algorithms that only consider intensity of the image. An image is mapped to a set of blocks represented by their dominant colors and average intensities. The dominant color is defined by hue and saturation with the hue value adjusted to make the principal colors more uniformly distributed. The average intensity is extracted from the Y component in the YCbCr space. By quantizing the color and intensity components, a feature vector is formed in a cylindrical coordinate system for each image block, which may be used to generate an intermediate hash. Euclidean distance is modified and a similarity metric introduced to measure the degree of similarity between images in terms of the color-intensity features. This is used to validate effectiveness of the proposed feature vector. Experiments show that the color-intensity feature is robust to normal image processing while sensitive to malicious alteration, in particular, color modification. 相似文献
6.
基于主分量分析的数字水印 总被引：7，自引：0，他引：7
王朔中 《上海大学学报(英文版)》2000,4(1):22-26
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7.
王朔中 《上海大学学报(英文版)》2002,6(2):149-153
Different digital watermarking techniques and their applications are briefly reviewed.Solution to a practical problem with visible image marking is presented,together with experimental results and discussion.Main focusis on reduction of error caused by the mark addition and subtraction.Image classification based on its mean gray level and adjustment of out-of-range gray levels are implemented. 相似文献
8.
建立在MATLAB平台上的数字图像处理教学实验系统 总被引：4，自引：0，他引：4
介绍一种用可视化数值计算软件实现的“数字图像处理”教学实验系统，该系统内容丰富、覆盖面广，界面友好生动、交互性强，适用于“数字图像处理”课程的教学。 相似文献
9.
利用边缘像素负载信息的二值图像密写 总被引：4，自引：0，他引：4
We present a novel scheme for embedding secret data into a binary image without introducing noticeable artifacts. Unlike some block-based methods, the proposed scheme encodes the secret bits directly into boundary pixels by checking each pixel of the cover image in a pseudo-random order for embedding eligibility. A set of rules ensures correct identification of data-carrying pixels in blind extraction. The proposed scheme does not generate isolated dots, and can incorporate various coding methods such as matrix encoding to further improve the embedding performance. It is shown that up to one fourth of the boundary pixels may be used to carry secret data. Experimental results indicate that the method can achieve good visual quality with fairly large data capacity. 相似文献
10.
王朔中 《上海大学学报(英文版)》2003,7(4):384-388
1 Introduction Indigitallibrariesthereistheneedtodevelopef fectivetechniquesappliedtotheimagesto protectcopyright.Digitalwatermarkthatisvisible ,robustanddifficulttoremoveisthereforeaddedtoimagestodiscouragecopyrightinfringement[1] .Thoughvisiblewatermarkingreducesthecommercialvalueofthehost information ,itdoesnothoweverattractpiratesthuspreventingtheimagefromtheft[1 6 ] .Manyre searcheshavebeencarriedoutondigitalwatermark ing .Fewerstudies,however ,havebeenreportedonvisiblewatermarkingasco… 相似文献