共查询到20条相似文献，搜索用时 764 毫秒
1.
We studied the variation of image entropy before and after wavelet decomposition, the optimal number of wavelet decomposition layers, and the effect of wavelet bases and image frequency components on entropy. Numerous experiments were done on typical images to calculate （using Matlab） the entropy before and after wavelet transform. It was verified that, to obtain minimal entropy, a three-layer decomposition should be adopted rather than higher orders. The result achieved by using biorthogonal wavelet decomposition is better than that of the orthogonal wavelet decomposition. The results are not directly proportional to the vanishing moment, however. 相似文献
2.
Watermarking is an effective approach to the copyright protection of digital media such as audio,image,and video.By inspriation from cryptography and considering the immensity of the set of all possible wvaelets,it is presented that in wavelet domain watermarking,the associated wavelet can be considered as the private key for encrypting the wavtermark so as to enhance the security of the embedded mark.This idea is partly supported by the fact that from computational complexity viewpoint.It is very time-consuming to search over the immense set of all candidate wavelets for the right one if no a priori knowledge is known about it .To verify our proposal,the standard image“Lena”is first watermarked in a specific wavelet domain,the watermark recovery experiments are then conducted in the wavelet domain for a set of wavelets with the one used for mark embedded in it ,separately.It follows from the experimetal results that the mark can be recovered only in the right wavelet domain,which jusstifies the suggestion. 相似文献
3.
Block-wise fragile watermarks can be used to reveal maliciously tampered areas in multimedia products. However a forged content containing a cloned fragile watermark can be constructed by using a series of watermarked data. To defeat this type of counterfeit attack, a novel fragile watermarking technique is proposed in which different pseudo-random data are selected for different host products, and the generated fragile watermark is dependent upon the selected information. While inserting the fragile watermark, the 相似文献
4.
In this paper, a CMOS image sensor(CIS) is proposed, which can accomplish both decorrelation and entropy coding of image compression directly on the focal plane. The design is based on predictive coding for image decorrelation. The predictions are performed in analog domain by 2×2 pixel units. Both the prediction residuals and original pixel values are quantized and encoded in parallel. Since the residuals have a peak distribution around zero,the output codewords can be replaced by the valid part of the residuals' binary mode. The compressed bit stream is accessible directly at the output of CIS without extra disposition. Simulation results show that the proposed approach achieves a compression rate of 2. 2 and PSNR of 51 on different test images. 相似文献
5.
Ground textures seriously interfere with the exact identification of grinding damage. The common nondestructive testing techniques for engineering ceramics are limited by their difficulty and cost. Therefore, this paper proposes a global image reconstruction scheme in ground texture surface using Fourier transform (FT). The lines associated with high-energy frequency components in the spectrum that represent ground texture information can be detected by Hough transform (HT), and the corresponding high-energy frequency components are set to zero. Then the spectrum image is back-transformed into the spatial domain image with inverse Fourier transform (IFT). In the reconstructed image, the main ground texture information has been removed, whereas the surface defects information is preserved. Finally, Canny edge detection is used to extract damage image in the reconstructed image. The experimental results of damage detection for the ground texture surfaces of engineering ceramics have shown that the proposed method is effective. 相似文献
6.
Multipurpose audio watermarking algorithm 总被引：1，自引：0，他引：1
To make audio watermarking accomplish both copyright protection and content authentication with localization, a novel multipurpose audio watermarking scheme is proposed in this paper. The zero-watermarking idea is introduced into the design of robust watermarking algorithm to ensure the transparency and to avoid the interference between the robust watermark and the semi-fragile watermark. The property of natural audio that the VQ indices of DWT-DCT coefficients among neighboring frames tend to be very similar is utilized to extract essential feature from the host audio, which is then used for watermark extraction. And, the chaotic mapping based semi-fragile watermark is embedded in the detail wavelet coefficients based on the instantaneous mixing model of the independent component analysis （ICA） system. Both the robust and semi-fragile watermarks can be extracted blindly and the semi-fragile watermarking algorithm can localize the tampering accurately. Simulation results demonstrate the effectiveness of our algorithm in terms of transparency, security, robustness and tampering localization ability. 相似文献
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8.
A neural-statistical approach to the reconstruction of novel viewpoint image general regression neural networks(GRNN) is presented.Different color value will be obtained by watching the same surface point of an abject from different viewpoints due to specular reflection,and the difference is related to the position of viewpoint.The relationship between the position of vewpoint and the color of image is non-linear,neural network is introduced to make curve fitting,where the inputs of neural network are only a few calibrated images with obvious specular reflection.By training the neural network,network model is obtained.By inputing an arbitrary virtual viewpoint to the model,the image of the virtual viewpoint can be computed.By using the method presented here,novel viewpoint image with photo-realistic property can be obtained,especially images with obvious specular reflection can accurately be generated.The method is an image-based rendering method,geometric model of the scene and position of lighting are not needed. 相似文献
9.
In this paper, a novel reconstruction technique based on level set method and algebraic reconstruction technique is proposed for multiphase flow computed tomography (CT) system. The curvature-driven noise reduction method is inserted into the conventional iteration procedure of algebraic reconstruction technique to improve the image quality and convergence speed with limited projection data. By evolving the image as a set of iso-intensity contours after each updation, the sufficient number of iterations for acceptable results is reduced by 80%-90%, while the image quality is enhanced obviously. Quantitative evaluation of image quality is given by using both relative image error and correlation coefficient. The resultant images can be utilized to detect flow regimes for monitoring industrial multiphase flow. Laboratory results demonstrate the feasibility of the proposed method. Phantoms of four typical flow regimes can be reconstructed from few-view projection data efficiently, and the corresponding image errors and correlation coefficients are acceptable for the cases tested in this paper. 相似文献
10.
成思源 《重庆大学学报(英文版)》2003,2(1)
1. Introduction The active contour model (also called snake) was first proposed by Kass [1] and can be used in many image analysis and computer vision applications such as edge detection, motion tracking, image matching, and 3-D reconstruction. A snake is a energy-minimizing curve controlled by internal and external forces. Internal forces act as a smoothness constraint, and external forces guide the snake toward image features that are of interest. B-spline representation of active contour c… 相似文献
11.
提出一种基于混沌映射的小波域数字图像水印新算法。将含有版权信息的二值图像作为水印,利用两个混沌映射的切换得到一个混沌序列,用其对水印图像进行加密。并用二维混沌映射对嵌入位置进行加密。算法根据HVS特性得到嵌入点的局部掩模函数,实现了水印在原始图像小波域中的自适应嵌入。实验结果证明该算法具有良好的鲁棒性。 相似文献
12.
基于小波包分解的自适应盲脆弱水印算法 总被引：1，自引：0，他引：1
信丽萍 《宁夏师范学院学报》2009,30(6):52-55
提出了基于图像内容自嵌入功能的脆弱水印算法．算法的新颖之处在于能区分图像内容、水印还是两者同时被篡改,由原图像高7位的一级小波低频系数量化得压缩图像,转换成二进制作为水印,混沌置乱加密后嵌入到原图像的LSB．认证时,由认证图像高7位制作的水印与提取水印的差值来确定图像是否遭到窜改,可定位篡改位置．实验结果表明：与Y-M算法相比峰值信噪比提高了5个dB,与WONG算法相比峰值信噪比提高了3个dB,实现了盲检测,而且该算法能够检测常见的攻击如噪声、几何剪切、滤波等． 相似文献
13.
HU Yuping YU Shengsheng ZHOU JingLi SHI Lei College of Computer Science Technology Huazhong University of Science Technology Wuhan P.R. China 《重庆大学学报(英文版)》2004,3(1):34-38
1.IntroductionInrecentyears,digitalimagewatermarkingtechni-queshavegrowndramatically.Digitalimagewater-markingisconcernedwithhidinginformationintoadigitalimage.Thisinformationmaybeusedforvariousapplicationssuchasauthentication,copyright,andproofofownership.Insomeapplicationsitisrequirednotonlytoidentifytherightfuluserofanimage,butalsotoembedsomeadditionalinformation.Forexample,incopyrightprotectionapplication,thewatermarkmaycontainadate,atime,aserialnumber,oranidentificationoftherightfuluser.… 相似文献
14.
应用小波变换实现数字水印 总被引：2，自引：0，他引：2
提出了一种利用小波变换实现数字水印的方法.其优点是良好的稳健性和层次性.这种算法充分利用小波变换的特点,把原始图象分解成多频段的图象来嵌入水印.检测时,把加了水印的图象塔式分解,通过计算处理每一层取得所有的有关信息. 相似文献
15.
提出一种基于小波提升的水印算法,将载体图像的亮度分量进行一级提升小波分解,分解之后再对其部分DCT系数进行一定的量化调制,将水印信息通过量化过程嵌入到载体图像中.由于对水印图像进行了置乱变换,消除了像素间的空间相关性,进一步提高了水印算法的安全性和抗攻击能力. 相似文献
16.
针对静止的自然图像,提出了一种基于有限脊波变换-Finite Ridgelet Transform(FRIT)域的水印算法．该算法利用二进小波提取原图像的模值图像之后,再对它进行分块,并分别对各个子块进行FRIT,最后把经过扩展谱技术处理得到的水印嵌入到每个子块能量最高的脊波系数中。水印的检测利用了相关函数法,且实现了水印的盲检测。实验证明该算法具有较强的鲁棒性。 相似文献
17.
提出了一个新的DWT域数字水印算法。该算法利用双密钥调制方法,在载体图像的低频子带嵌入置乱水印,水印提取不需要原始图像。实验结果表明水印具有良好的鲁棒性和不可见性。 相似文献
18.
基于模运算的数字水印算法研究 总被引：2，自引：0，他引：2
李瑛 《鞍山师范学院学报》2003,5(4):83-85
介绍了数字水印的分类，提出了一种基于模运算的数字水印算法。该算法具有很好的性能：水印隐藏的效果好，凭借人类的视觉系统无法看出与原图像的差别；可以有效地抵抗JPEG等压缩编码的破坏；可以依靠部分图像检测水印，在图像受到损坏的情况下，仍可以检测到水印信息；检测水印时受到口令的限制，不知道口令的人无法正确恢复水印；检到水印时不需要原始图像。 相似文献
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20.
提出了一种基于有限脊波变换域实现图像水印的方法。其优点是良好的稳健性和层次性的检测方法。这种算法充分利用有限脊波变换的特点,把原始图像和水印分解成多频段的图像来嵌入水印。检测时,把加了水印的图像分解,通过计算处理每一层取得所有的有关信息。 相似文献