DWT系数分块的零水印方案

提出了一种基于Logistic混沌序列、Arnold变换、DWT系数分块的零水印算法.该算法首先将载体图像进行DWT变换,将低频子带进行分块,对每个系数块的均值进行量化、模运算得到载体图像的特征信息,然后将特征信息与预处理过的水印做异或运算,得版权信息,最后把版权信息注册到IPR（intellectual property right）数据库中.实验证明,该算法对加性噪声、有损压缩、裁剪等攻击都具有很好的鲁棒性.     

一种抗几何攻击的图像零水印方案

提出一种抗几何攻击的图像零水印方案。该方案不改变原始图像的数据，利用图像几何不变矩构造水印，较好地解决了水印的鲁棒性与不可感知性之间的矛盾。实验证明，水印方案对几何变换及常见的图像处理具有较好的鲁棒性。     

一种基于小波变换的􀀂 图像数字水印技术

针对图像数字水印技术，提出了一种实用的基于小波变换的图像数字水印嵌入方法，并在Matlab下得以验证。试验结果表明，该算法对图像非整体性的破坏有很强的鲁棒性。     

基于非下采样轮廓小波变换的图像去噪

针对采用下采样滤波器结构的轮廓波、轮廓小波在图像去噪过程中会引入伪吉布斯现象,利用小波变换(WT)和非下采样方向滤波器组(NDFB)构造了一种新的多尺度、多分辨率图像的非下采样轮廓小波变换(NWCT)。WT去除了拉普拉斯金字塔滤波器(LPF)的计算冗余,NDFB保证了该变换具有平移不变性。为了验证该变换的有效性,对其进行了图像去噪实验。实验结果表明,所提出方法能获得比WT、轮廓波变换(CT)、轮廓小波变换(WCT)更高的峰值信噪比(PSNR),并且能够很好地抑制伪吉布斯现象。     

一种改进的消零频傅里叶变换轮廓术

为提高傅里叶变换轮廓术(FTP)的测量精度和范围,提出了一种改进的消零频FTP。将两幅随机相移正弦条纹通过DLP投影仪投射到待测物体上,由CCD相机采集受物体形貌调制的变形光栅条纹图,将采集的两幅条纹图相减得到无零频的条纹差图。对条纹差图进行快速傅里叶变换(FFT)后,通过简易滤波器提取基频成分,将其与彩色条纹或复合光栅投影相结合,可实现单次投影。理论和实验证明了本方法的可行性。     

一种改进的基于小波变换的快速EZW算法

研究了一种适合在高速DSP上运行的基于小波变换的快速嵌入式零树编码（EZW）算法。通过分析传统EZW的数据压缩流程以及DSP的处理机制,对EZW算法进行了改进,使之在DSP上运行的速度得到了极大的提高,并已在某高输入数据率的图像压缩项目上使用,效果良好。     

基于Contourlet和哈达玛变换的图像零水印算法

为了改善图像水印的鲁棒性和不可见性,提出一种零水印方案。首先将原始载体图像进行Contourlet分解,对其低频子图进行分块哈达玛变换,利用哈达玛变换后系数的均值来生成构造图像,再将其与置乱后的水印一起输入细胞神经网络(CNN),得到注册图像。实验结果表明该方法具有较好的鲁棒性;而且算法复杂度较低,便于实时处理。     

基于小波变换和相对量化的图像数字水印算法

提出了一种基于分块小波变换和相对量化的图像数字水印算法。由于在算法中采用了量化嵌入策略,从而在提取水印时无需原始图像和原始水印。实验结果表明,该算法对嵌入的水印具有很好的透明性,对亮度和对比度调整攻击具有非常强的稳健性,对JPEG压缩、重采样、颜色抖动、平滑和加噪声等常见的图像处理攻击具有很强的稳健性,并且算法思想简单、步骤简便和容易实现。     

一种基于零树的多码率小波图象编码方法

本文研究以零树方法进行小波图象压缩编码，在零树编码各级小波系数前，根据不同分解级小波系数幅值间的相关特性，通过以树结构对小波系数的能量人三测与排序，不仅优化了码率的分配，提高了编码图象ＰＳＮＲ约０．３－０．５ｄＢ，而且加速了编码过程各纳１０％，同时该编码方案仍保零树编码产生嵌入式码流，支 持多码率图象解码。     

基于图像小波变换低频系数的数字水印算法

提出一种基于小波变换且具有图像自适应性的数字水印算法.通过小波变换将图像分解成不同空间与频率的系数,这些系数之间存在一种树结构关系,利用树结构关系对最低频系数进行分类,对不同类采用不同的嵌入对策,将水印信号嵌入在最低层逼近系数中,而现有基于小波变换的算法将水印嵌入在各个方向的中频或高频系数中.实验结果表明,该算法具有不可见性,对于通常的图像失真具有较好的鲁棒性,说明最低频成分并不是水印的禁区.     

视觉密码方案概述

视觉密码(VC)是一种用于分享秘密图像的加密方案,与传统的密码技术相比具有简单性、安全性、隐蔽性等优点.其加密是将图像编码为分享,将分享打印在透明胶片上或以数字形式存储;其解密过程是对分享进行叠加,然后通过人类的视觉能力来实现.本文介绍了视觉密码的基本概念和各种不同的视觉密码方案,以及每种方案中使用的技术.此外,对视觉...     

A zero-watermark algorithm for multiple images based on visual cryptography and image fusion

At present, it is difficult for the multiple images zero-watermark algorithm to protect all the images in the image set, and repeated operations will reduce the efficiency of the algorithm. To solve these issues, the proposed algorithm can design a reasonable copyright protection scheme according to the number of images in the image set to realize the protection of all images, and reduce the cost of time and storage. The gray-weighted average image fusion method is used to fuse multiple normalized standard images into one image. The LWT(Lifting the Wavelet Transform)-QR decomposition is applied to the effective area of the fusion image to obtain the robust feature image. Non-extended visual cryptography is used to enhance the security of the algorithm. A zero-watermark image is obtained by using the XOR manipulation for the feature image and the public shared image. Experimental results demonstrate that the proposed algorithm has good performance.     

Distributed three-level QR codes based on visual cryptography scheme

Owing to the large storage and fast machine recognition, QR codes have been widely utilized in many fields such as mobile payment, website navigation and user identity authentication. However, any QR code reader can access to the message contained in the QR code, the security becomes a major challenge to QR codes for privacy usage scenarios. Moreover, the management of QR codes for users are also inconvenient, since the human vision is hard to distinguish a QR code from the others. To solve the security and management problems, we propose the three-level QR codes for a group of participants. The first-level management information and the second-level public information are recognizable for the human vision and QR code reader device, respectively. The third-level privacy information is protected using visual cryptography scheme, and can be decoded using simple and non-cryptography computations. Furthermore, the shares can be stored or transferred in not only e-format but also print-format and photo-format, leading to the broad applicability. Experimental results and analysis demonstrate that the proposed scheme can encode three-level information into several distributed QR codes, and has more advantages compared with the previous schemes.     

Improving the visual quality of size invariant visual cryptography scheme

In order to reduce the pixel expansion of visual cryptography scheme (VCS), many size invariant visual cryptography schemes (SIVCS’s) were proposed. However, most of the known SIVCS’s have bad visual quality and thin line problems, hence the known SIVCS’s are only suitable to encrypt coarse secret images. In this paper, we notice that the variance of the darkness levels of the pixels also reflects the visual quality of the recovered secret image, as well as the average contrast. We verify, analytically and experimentally, the effectiveness of the variance to be a criterion for evaluating the visual quality of the recovered secret image. Furthermore, we propose two multi-pixel encryption size invariant visual cryptography schemes (ME-SIVCS’s) which improve the visual quality of the recovered secret image by reducing the variance of the darkness levels. In addition, the proposed ME-SIVCS’s can be used to encrypt fine secret images since they avoid some known thin line problems. Experimental results and comparisons are also given to show the effectiveness of the proposed ME-SIVCS’s. Finally, we give suggestions on obtaining good visual quality for the recovered secret image.     

A digital signature-based visual cryptography scheme for image discrimination and management

Visual cryptography is a cryptographic technique which emerges in the information security domain in recent years. Each of the sharing sub-keys may be a stochastic noise image or a significative image with no information on the original key. But a mass of sub-keys have to be saved actually, which faces the problem of inconvenient discrimination and management. This paper presents a visual cryptography scheme based on the digital signature for image discrimination and management, ap-plying the digital signature and the time-stamp technology to the visual cryptography scheme. The scheme both solves the problem on the storage and management of the sharing sub-keys, increases the verification of image contents, thus enhances the validity of storage and management without security effect.     

采用小波变换的鲁棒隐形水印算法

本文提出了一种小波域透明图像水印算法,算法将一个二进制随机水印信号内嵌到一组按重要性选出的小波系数中,为了使透明水印具有较高的鲁棒性,内嵌过程将水印信号将为量化噪声嵌入小波零树编码的数字图像,实验获得了良好的结果。     

双重功能图像水印算法

提出一种能同时实现内容认证和版权保护双重功能的图像水印算法.首先,对原始图像进行分块奇异值分解(SVD),计算所有子块最大奇异值的均值,通过比较各子块的最大奇异值与所有子块最大奇异值的均值间的数值关系产生鲁棒零水印序列.然后,对原始图像进行分块离散余弦变换(DCT).调整图像子块DCT高频系数的数值大小,建立同一子块两...     

一种神经网络自适应数字图像水印算法

本文利用人工神经网络模拟人眼视觉特性，根据图像特征自适应地确定图像DCT变换各系数所能嵌入的水印强度。实验表明，使用该方法能在确保水印不可见的同时提高水印的嵌入强度，从而可提高水印的顽健性，且该方法具有很好的适应性。     

XOR-based visual cryptography scheme with essential shadows

Visual cryptography scheme with essential shadows (EVCS) is of great significance since it provides different levels of the importance to shadows. In this paper, we propose a general construction method for (t, s, k, n)-VCS with essential shadows based on XOR operation ((t, s, k, n)-EXVCS), which originates from the partition of access structure. The secret image is encrypted into s essential shadows and n-s non-essential shadows. Any k shadows including at least t essentials can cooperate to decode the secret image and the decoding process is implemented by XOR operation on the involved shadows. Our scheme achieves perfectly reconstruction of secret image in the revealed image and the less size of shadows and revealed images. The experiments are conducted to testify the feasibility and practicability of the proposed scheme.