Radon变换域的鲁棒图像Hash算法研究

针对数字图像内容认证的问题,提出了一种基于Radon变换域的鲁棒图像Hash算法。该算法在Radon变换域提取图像平移、缩放不变的矩特征,将矩特征的离散傅里叶变换系数作为图像的Hash值。离散傅里叶变换可实现抗图像旋转操作,并可降低图像Hash的维数。为了增加安全性,整个特征提取过程都是基于密钥进行的。理论分析证明Radon变换域的不变矩特征对一般的图像处理操作,特别是平移、缩放、旋转等几何操作有极好的不变性。实验结果表明提出的算法几乎可以容忍所有的图像内容保存操作,比如缩放、旋转、JPEG压缩、滤波和加噪等,同时对视觉上有明显失真或根本不相似的图像有高度的敏感性。     

基于CL多小波变换和组合位平面理论的秘密信息共享算法

针对信息隐藏算法容量和不可见性与鲁棒性矛盾的特点,提出了一种新的基于Chui-Lian(CL)多小波变换和组合位平面(CBP)理论的数字图像载体预处理算法,并将该算法用于以数字图像为载体的信息隐藏,以实现秘密通信和图像共享。其中,CL多小波变换能够将载体图像划分为4个能量等级不同的最低分辨率子图像,组合位平面理论可将子图像解析为不同的位平面层次,在隐藏秘密信息时,可根据最低分辨率子图和组合位平面的能量等级由高到低分别嵌入鲁棒信息、秘密信息和脆弱信息。实验结果表明,在25%的嵌入率时,与基于离散余弦变换和最低有效位方法的信息隐藏算法（DCT-LSB）、基于离散小波变换和最低有效位方法的信息隐藏算法（DWT-LSB）相比,所提算法针对若干常见攻击的鲁棒性有一定程度提升,峰值信噪比（PSNR）分别提高了37.16%和20.00%。     

小波局部适应插值的图像超分辨率重建

针对单帧低分辨率图像的超分辨率重建问题,提出一种改进的小波局部适应插值的超分辨率重建方法,该方法能够弥补重建图像边缘不平滑的缺陷。结合小波变换与可分离高低频信息的特性,提出一种综合两者优点的单帧图像超分辨率重建算法。实验结果表明,采用该算法得到的重建图像不仅能较好地保留原始图像的细节信息,提高图像的空间分辨率,并能提高图像的峰值信噪比,更适合人眼视觉系统。     

一种基于多小波域与 DCT 的数字盲水印算法

研究一种新的数字图像盲水印算法.针对目前基于的离散小波变换算法和 DCT 变换算法中,对噪音和几何变形攻击抵抗力弱,需要原始水印的缺点,提出了一种利用多小波域和离散余弦变换相结合的数字盲水印算法.结合离散多小波变换的多分辨率特性和离散余弦变换所固有的特征,首先对原灰度图像 DMWT 变换,而后对低频系数作分块 DCT 变换,再将经过 Arnold 预处理的二值图像水印信息分别嵌入到经过 DCT 变换的较好的块中.提取水印时不需要原始图像的参与,实现了盲水印提取.实验结果表明,嵌入算法容易实现,并增强了水印的稳健性和不可见性,算法对锐化、JPEG 压缩、剪切和噪声等常见的图像攻击有较好的鲁棒性.     

基于DWT的图像水印算法研究

提出了一种基于离散小波变换的水印算法。水印采用文本图像水印,将原始图像和水印分别进行3级小波变换,为了保证水印的安全性,将水印变换域各子图分别进行置乱或加密处理。将水印经处理后的各级变换系数重复嵌入原始图像各级变换系数的不同位置。在检测时,提出采用多方案水印提取算法以适应不同的攻击。实验表明对缩放、剪切、JPEG或JPEG2000压缩等图像退化处理或攻击均具有较强的鲁棒性。     

一种基于DWT和DCT的盲灰度级水印算法*

提出一种新的盲灰度级水印算法.它充分利用离散小波变换的多分辨率特性和离散余弦变换的能量压缩能力,将预处理后的灰度水印图像隐藏在原始图像DCT系数量化值的奇偶性中,在水印的提取过程中不需要原始图像的参与.实验结果表明,该算法对图像剪切、JPEG有损压缩、中值滤波等攻击有很强的鲁棒性,对旋转、噪声等攻击也具备了一定的抵抗能力.     

基于多分辨率奇异值分解的图像融合

提出一种新的基于多分辨率奇异值分解（ MSVD）图像融合算法。算法对源图像进行MSVD处理,使其分解为互不相关的平滑和细节分量,并对平滑分量进行多层次的分解与处理。类似于小波变换,多分辨率奇异值分解的基本思想是在平滑分量的每一层上用奇异值分解（ SVD）来取代滤波,最终利用融合规则对图像进行MSVD融合。利用5种评价算子来评价算法,得到的融合效果很好。与基于小波分解的算法相比,算法计算简单、实时性突出,对复杂、高像素图像处理更简单方便。     

多分辨率图像序列的超分辨率重建

针对不同焦距下拍摄的多分辨率尺度的图像序列,本文提出了一种基于尺度不变特征转换(Scale invariant feature transform, SIFT)和图像配准的超分辨率(Super resolution, SR)图像盲重建算法.首先提取图像SIFT特征点,然后用向量夹角余弦进行特征描述符向量的初匹配,并用随机抽样一致性 (Random sample consensus, RANSAC)算法消除误匹配提高配准精度.计算变换参数后,将低分辨率图像(Low-resolution, LR)像素点映射到高分辨率(How-resolution, HR)网格,最后利用像素可信度加权算法填充缺失像素值,重建更高分辨率的图像.实验表明, 本文算法能精确估计图像序列的缩放因子,可以有效处理仿射变换模型,对配准误差也具有一定的鲁棒性.算法从实质上提高了多分辨率尺度图像序列的分辨率,尤其在低分辨率帧数较少可用于重建的信息量严重不足时也能获得比较满意的重建效果.     

网格图像水印技术的研究*

针对网格环境中图像信息资源的版权保护问题,提出了一种可应用于网格环境下的基于离散小波变换DWT和扩频技术的有意义数字水印算法.该算法在传统的基于DWT和扩频技术的有意义数字水印算法中,利用小波变换的多分辨率特性来进行图像的小波分解和重构,利用数字扩频技术来实现嵌入和检测水印.实验证明选择频域嵌入水印可以获得更好的图像保真度,并且比在空域中的水印算法更稳健,可实现在网格环境下的版权保护.     

实离散分数Krawtchouk变换及其在数字图像水印中的应用

目的传统Krawtchouk变换处理图像时存在变换域信息表示单一、不可调节等问题,传统分数阶Krawtchouk变换处理实信号表示有冗余等问题。为了构造更加灵活的图像变换域表示,提出了实离散分数阶Krawtchouk变换,并应用于数字图像水印。方法利用对传统Krawtchouk变换矩阵特征值分解的方式,通过对分解后的特征值矩阵的实矩阵分数化构造得到了实离散分数阶Krawtchouk变换的变换矩阵,从而构造出实离散分数阶Krawtchouk变换。然后,利用所提变换从实数域变换到实数域这一特性,提出了在实离散分数阶Krawtchouk变换嵌入水印信息的图像水印算法。算法采用了图像分块处理的方式,对每个图像块的实离散分数Krawtchouk变换系数进行奇异值分解,将水印信息嵌入奇异值分解矩阵中,然后进行逆向实离散分数阶Krawtchouk变换得到嵌入水印后的图像。结果通过比较所提实离散分数阶Krawtchouk变换域水印算法和传统Krawtchouk变换域水印算法,提取水印的平均错误率在中值滤波、均值滤波、高斯滤波、JPEG压缩和缩放攻击下,分别降低了12.39%、10.04%、18.50%...     

Multiresolution modeling techniques in CAD

This paper investigates new wavelet-based multiresolution modeling techniques in CAD. Models in the system are represented by endpoint-interpolating B-spline functions. Wavelet deformation techniques are extended to include synthesis editing and detail blending from previous sweep editing and fractional editing methods. Application of multiresolution editing to multiple patches of complex topology is investigated. An algorithm for multi-patch deformation is developed by enforcement of G⁰ continuity between adjacent patches. After editing G¹ continuity may be recaptured by numerical optimization of the error vectors along boundary seams. A simple CAD interface is implemented for B-spline patch acquisition based on reverse engineered data and layer based modeling and a moving cursor plane is used for three-dimensional (3D) editing. Design examples are presented to illustrate the 3D wavelet editing capability. The developed wavelet deformation techniques can be a useful complement to current CAD systems by providing powerful new modeling and editing capabilities.     

Multiresolution morphing for planar curves

We present a multiresolution morphing algorithm using ``as-rigid-as-possible' shape interpolation combined with an angle-length based multiresolution decomposition of simple 2D piecewise curves. This novel multiresolution representation is defined intrinsically and has the advantage that the details' orientation follows any deformation naturally. The multiresolution morphing algorithm consists of transforming separately the coarse and detail coefficients of the multiresolution decomposition. Thus all LoD (level of detail) applications like LoD display, compression, LoD editing etc. can be applied directly to all morphs without any extra computation. Furthermore, the algorithm can robustly morph between very large size polygons with many local details as illustrated in numerous figures. The intermediate morphs behave natural and least-distorting due to the particular intrinsic multiresolution representation.     

A Coordinate-Invariant Approach to Multiresolution Motion Analysis

Multiresolution motion analysis has gained considerable research interest as a unified framework to facilitate a variety of motion editing tasks. Within this framework, motion data are represented as a collection of coefficients that form a coarse-to-fine hierarchy. The coefficients at the coarsest level describe the global pattern of a motion signal, while those at fine levels provide details at successively finer resolutions. Due to the inherent nonlinearity of the orientation space, the challenge is to generalize multiresolution representations for motion data that contain orientations as well as positions. Our goal is to develop a multiresolution analysis method that guarantees coordinate-invariance without singularity. To do so, we employ two novel ideas: hierarchical displacement mapping and motion filtering. Hierarchical displacement mapping provides an elegant formulation to describe positions and orientations in a coherent manner. Motion filtering enables us to separate motion details level-by-level to build a multiresolution representation in a coordinate-invariant way. Our representation facilitates multiresolution motion editing through level-wise coefficient manipulation that uniformly addresses issues raised by motion modification, blending, and stitching.     

基于灰度共生矩阵纹理特征的SAR图像分割

同时考虑SAR图像局部灰度均值和方差及像素空间分布特征等统计量,在以灰度共生矩阵产生的纹理统计量为特征所生成的图像上,建立多分辨双Markov-GAR模型,采用多分辨MPM的参数估计方法及相应的无监督分割算法,对SAR图像进行纹理分割。该方法用于一些高分辨SAR图像,其分割精度及分割边缘的平滑度均优于基于灰度图像上的多分辨双Markov-GAR模型纹理分割。     

基于小波的B样条曲线多分辨表示及编辑

多分辨表示方法为曲线提供了更为灵活的表达方式,使得我们可以在不同分辨率下对曲线进行编辑,小波技术是实现曲线多分辨表示的一种新颖方法,已有许多论文从理论上论述了这项技术,文中从几何概念出发,由浅入深地论述了基于小波的准均匀三次B样条曲线多分辨表示的原理及其实现,并通过实例描述了B样条曲线的多分辨编辑。     

一种基于分数阶偏微分方程的图像放大算法

针对传统图像放大算法的不足之处,将物理意义鲜明的分数阶偏微分理论引入到图像放大算法中,提出一种新的基于分数阶偏微分方程的图像放大算法,使得放大图像的轮廓更加清晰,同时能够有效保留放大图像的细节边缘特征。仿真实验结果表明,该方法对比传统图像放大算法在放大图像的同时也增强图像的清晰度和对比度。     

Interactive sketch generation

In this paper, we propose an interactive system for generating artistic sketches from images, based on the stylized multiresolution B-spline curve model and the livewire contour tracing paradigm. Our multiresolution B-spline stroke model allows interactive and continuous control of style and shape of the stroke at any level of details. Especially, we introduce a novel mathematical paradigm called the wavelet frame to provide essential properties for multiresolution stroke editing, such as feature point preservation, locality, time-efficiency, good approximation, etc. The livewire stroke map construction leads the user-guided stroke to automatically lock on to the target contour, allowing fast and accurate sketch drawing. We classify the target contours as outlines and interior flow, and develop two respective livewire techniques based on extended graph formulation and vector flow field. Experimental results show that the proposed system facilitates quick and easy generation of artistic sketches of various styles.     

Multiresolution for Closed Curves and Surfaces Using Wavelets

Multiresolution modeling is becoming a powerful tool for fast display, and geometric data compression and transmission of complex shapes. Most of the existing literatures investigating the multiresolution for B-spline curves and surfaces are concentrated on open ones. In this paper, we focus on the multiresolution representations and editing of closed B-spline curves and surfaces using wavelets. A repetition approach is adopted for the multiresolution analysis of closed B-spline curves and surfaces. Since the closed curve or surface itself is periodic, it can overcome the drawback brought by the repetition method, i.e. introducing the discontinuities at the boundaries. Based on the models at different multiresolution levels, the multiresolution editing methods of closed curves and surfaces are introduced. Users can edit the overall shape of a closed one while preserving its details, or change its details without affecting its overall shape.     

Fast variational design of multiresolution curves and surfaces with B-spline wavelets

Multiresolution modeling provides a powerful tool for complex shape editing. To achieve a better control of deformations and a more intuitive interface, variational principles have been used in such multiresolution models. However, when handling multiresolution constraints, the existing methods often result in solving large optimization systems. Hence, the computational time may become too excessive to satisfy the requirements for interactive design in CAD. In this paper, we present a fast approach for interactive variational design of multiresolution models. By converting all constraints at different levels to a target level, the optimization problem is formulated and solved at the lower level. Thus, the unknown coefficients of the optimization system are significantly reduced. This improves the efficiency of variational design. Meanwhile, to avoid smoothing out the details of the shape in variational modeling, we optimize the change in the deformation energy instead of the total energy of the deformed shape. Several examples and the experimental results are given to demonstrate the effectiveness and efficiency of this approach.     

A Pyramid Approach to Motion Tracking

This paper presents a multiresolution approach to visual motion tracking. In the approach, the foveation mechanism of the human visual system is used to model the multiresolution information perception algorithms of a Transputer-based pyramid visual tracking system. The video images of a moving target are transformed into pyramidal data structures, each of those images consists of multiple image layers with different resolutions by a Gaussian pyramid generation algorithm. The tracking of a moving target over an image sequence is accomplished by performing a foveal search that is based on an iterative intensity pattern correlation along the multiple resolution levels of the Gaussian pyramids of two successive images. Analyses are given as to the efficiency and accuracy of our tracking algorithm, showing that the algorithm is over 160 times faster than conventional mono-resolution tracking methods, with the tracking error within one pixel. To demonstrate the superiority of the multiresolution tracking algorithm in the connection to parallel computation, a scheme for mapping the tracking algorithm into a Transputer-based pyramidal parallel computing structure is proposed in the paper. Experimental results demonstrate good performance of the proposed approach.