On normalized compression distance and large malware

Normalized Compression Distance (NCD) is a popular tool that uses compression algorithms to cluster and classify data in a wide range of applications. Existing discussions of NCD’s theoretical merit rely on certain theoretical properties of compression algorithms. However, we demonstrate that many popular compression algorithms do not seem to satisfy these theoretical properties. We explore the relationship between some of these properties and file size, demonstrate that this theoretical problem is actually a practical problem for classifying malware with large file sizes, and propose some variants of NCD that mitigate this problem.     

刺绣图案中直线和圆弧的矢量化研究

多数刺绣图案的基本组成图元是由线段和圆弧组成。针对它的录入问题,本文提出了一种从BMP图像格式到DXF图形格式转换的实现算法。首先通过扫描仪输入刺绣图案图像;然后利用图像处理和多项式拟和算法来实现图像到图形的矢量化;最后形成DXF文件格式。实验结果表明:该算法可有效地提高输图效率。     

Web-Based Remote Renderingwith IBRAC (Image-Based Rendering Acceleration and Compression)

Recent advances in Internet and computer graphics stimulate intensive use and development of 3D graphics on the World Wide Web. To increase efficiency of systems using 3D graphics on the web, the presented method utilizes previously rendered and transmitted images to accelerate the rendering and compression of new synthetic scene images. The algorithm employs ray casting and epipolar constraints to exploit spatial and temporal coherence between the current and previously rendered images. The reprojection of color and visibility data accelerates the computation of new images. The rendering method intrinsically computes a residual image, based on a user specified error tolerance that balances image quality against computation time and bandwidth. Encoding and decoding uses the same algorithm, so the transmitted residual image consists only of significant data without addresses or offsets. We measure rendering speed-ups of four to seven without visible degradation. Compression ratios per frame are a factor of two to ten better than MPEG2 in our test cases. There is no transmission of 3D scene data to delay the first image. The efficiency of the server and client generally increases with scene complexity or data size since the rendering time is predominantly a function of image size. This approach is attractive for remote rendering applications such as web-based scientific visualization where a client system may be a relatively low-performance machine and limited network bandwidth makes transmission of large 3D data impractical.     

Web 2D Graphics File Formats

The earliest Web browsers focussed on the display of textual information. When graphics were added, essentially only image graphics and image file formats were supported. For a significant range of applications, image graphics has severe limitations, for example in terms of file size, download time and inability to interact with and modify the graphics client-side. Vector graphics may be more appropriate in these cases, and this has become possible through the introduction of the WebCGM and Scalable Vector Graphics (SVG) formats, both of which are open standards, the former from ISO/IEC and W3C and the latter from W3C. This paper reviews the background to Web graphics, presents the WebCGM file format, and gives a more detailed exposition of the most recent format, SVG. The paper concludes with reflections on the current state of this area and future prospects.     

Steering Image Generation with Wavelet Based Perceptual Metric

It is often the case that images generated by image synthesis algorithms are judged by visual examination. The user resorts to an iterative refinement process of inspection and rendering until a satisfactory image is obtained. In this paper we propose quantitative metrics to compare images that arise from an image synthesis algorithm. The intent is to be able to guide the refinement process inherent in image synthesis. The Mean-Square-Error (MSE) has been traditionally employed to guide this process. However, it is not a viable metric for image synthesis control. We propose the use of a wavelet based perceptual metric which incorporates the frequency response of the Human Visual System. A useful aspect of the wavelet based metric is its ability to selectively measure the changes to structures of different sizes and scales in specific locations. Also, by resorting to the use of wavelets of various degrees of regularity, one can seek different levels of smoothness in an image. It is rare that such level of control can be obtained from a metric other than a wavelet based metric. We show the usefulness of our metric by examining its effectiveness in providing insights for common operations of an image synthesis algorithm (e.g., blurring). We also provide some examples of its use in rendering algorithms frequently used in graphics.     

Real reality

In its most basic form, computer graphics technology renders an image of the world from a model. Having refined techniques from vector graphics, computer graphics now includes improved methods to render realistic and informative visual images of models representing microcosms of interest. Computational technology includes mechanisms to compress, communicate and combine text, audio, graphics and video to provide a unified multimedia document. Users can now decide if they want to read a story, watch a video or combine information from multiple sources to create a personalized digital experience. So what future faces computer graphics and multimedia? Can we take the technology to still another level of reality? Let's assume we can expand the scope of computer graphics to produce and render a world model for information or entertainment that surpasses the visual, also representing sound, touch, smell and taste. Although seemingly far out now, I believe computer graphics and multimedia will combine and expand to make such a technology-real reality-possible. Virtual reality (VR) foreshadows this development. I believe real reality, or what may more accurately be called remote reality, lies just around the corner. Real reality will revolutionize our society in many ways. Unlike VR, real reality systems will let users experience and interact digitally with real environments using all the human senses. However, real reality experiences will remain free of time and space constraints. You will be able to experience a remote environment digitally at your convenience wherever you are     

一种用于隐写测评的图像纹理复杂度估计方法

在评估图像隐写算法安全性及隐写分析性能时,隐写嵌入率等参数是重要的评价指标,而图像纹理差异对评价的影响很容易被忽略。为此,基于图像高维统计模型,提出一种新的针对隐写应用的图像纹理复杂度度量方法,用于衡量图像间的纹理差异。根据纹理复杂度对图像进行分类,单独在每一类不同纹理复杂度的图像集上评估隐写分析的检测性能。实验结果表明,该方法能有效地评价隐写的安 全性。     

Computer graphics—Whence and hence

Computer Graphics is one of the most important, far-reaching, sophisticated, and glamorous endeavors of the computer field. It can be useful to every discipline that employs to advantage the computer. At the present time it is available for all the major computer areas—input, output, programming, and debugging. Whence did it originate? Exactly what is it and how can it be used? What are its future trends? These questions are considered in this article which divides Computer Graphics into two main divisions—passive and interactive. This article describes the most popular subdivisions of passive graphics—microfilm recorders and plotters—in detail. Computer Animation and Computer-generated movies as well as the main types of display devices are included under interactive graphics. This survey article considers the history of all the main types of computer graphics; discusses the typical hardware and main attributes as well as the advantages and disadvantages of each type; presents a section on computer-aided design, and a section on computer graphics professional groups and societies; and in its conclusion indicates some of the pit-falls of this powerful computing tool.     

Interactive Graphics for Computer Adaptive Testing

Interactive graphics are commonly used in games and have been shown to be successful in attracting the general audience. Instead of computer games, animations, cartoons, and videos being used only for entertainment, there is now an interest in using interactive graphics for ‘innovative testing’. Rather than traditional pen‐and‐paper tests, audio, video and graphics are being conceived as alternative means for more effective testing in the future. In this paper, we review some examples of graphics item types for testing. As well, we outline how games can be used to interactively test concepts; discuss designing chemistry item types with interactive 3D graphics; suggest approaches for automatically adjusting difficulty level in interactive graphics based questions; and propose strategies for giving partial marks for incorrect answers. We study how to test different cognitive skills, such as music, using multimedia interfaces; and also evaluate the effectiveness of our model. Methods for estimating difficulty level of a mathematical item type using Item Response Theory (IRT) and a molecule construction item type using Graph Edit Distance are discussed. Evaluation of the graphics item types through extensive testing on some students is described. We also outline the application of using interactive graphics over cell phones. All of the graphics item types used in this paper are developed by members of our research group.     

基于VB6．0和OpenGL的DXF文件读取与交互控制

DXF文件格式是传统图形开发中最常用的图形交换格式之一,众多第三方开发的图形软件均加入了对DXF文件的支持。为开发一套三维可视化仿真数据分析软件,首先就必须解决对DXF文件的读取及显示问题。文章详细分析了ASCII码格式DXF文件的数据结构特点,然后,使用VB6．0从中读取数据,并利用OpenGL的模型绘制和渲染功能,实现了三维模型的重构以及交互控制。这种处理方法既能满足快速建模的需要,又能高效地实现友好的交互功能。     

中国图形工程：2000

考虑到国内关于图形学研究及应用的论文分布于多种学术期刊上的特点,为了让图形学领域内的理论研究和开发人员对我国图形学研究进展有一个全面的了解,以及为读者楂阅相关文献提供方便,通过从我国国内2000年发表的有关计算机图形学论文,析出了304篇学术研究和技术应用论文,在根据内容进行分类的基础上撰写了中国图形工程的年度文献综述系列之六。     

Parallel processing of incremental ray tracing on a shared-memory multiprocessor

This paper presents a novel parallel-processing method for image synthesis using incremental ray tracing on a shared-memory multiprocessor workstation. The most efficient technique for image synthesis is ray tracing, proposed by Whitted in 1980. Ray-tracing algorithms are simple and can generate realistic images. However, they are time-consuming, since calculations of the intersections between objects and ray increase exponentially as the complexity of scenes increases. Fast image synthesis for animation is one of the most important topics in computer graphics. As the area of computer applications has broadened, the complexity of images to be synthesized has increased. Parallel processing of computer graphics is one way of achieving fast image synthesis. This paper describes a parallel processing technique for incremental ray tracing, which recalculates only the rays changed by moving objects in successive scenes of continuous image synthesis. The performance of parallel ray tracing was evaluated on the multiprocessor workstation TOP-1. Strategies for allocating pixels to processes under a multiprocess operating system on this workstation are discussed.     

Lattice Boltzmann based PDE solver on the GPU

In this paper, we propose a hardware-accelerated PDE (partial differential equation) solver based on the lattice Boltzmann model (LBM). The LBM is initially designed to solve fluid dynamics by constructing simplified microscopic kinetic models. As an explicit numerical scheme with only local operations, it has the advantage of being easy to implement and especially suitable for graphics hardware (GPU) acceleration. Beyond the Navier–Stokes equation of fluid mechanics, a typical LBM can be modified to solve the parabolic diffusion equation, which is further used to solve the elliptic Laplace and Poisson equations with a diffusion process. These PDEs are widely used in modeling and manipulating images, surfaces and volumetric data sets. Therefore, the LBM scheme can be used as an GPU-based numerical solver to provide a fast and convenient alternative to traditional implicit iterative solvers. We apply this method to several examples in volume smoothing, surface fairing and image editing, achieving outstanding performance on contemporary graphics hardware. It has the great potential to be used as a general GPU computing framework for efficiently solving PDEs in image processing, computer graphics and visualization.     

基于欧氏距离相关函数的多重分形谱算法

提出了一种基于欧氏距离相关函数计算多重分形谱的算法.介绍了基于测度理论的多重分形谱的定义,定义了基于欧氏距离相关函数的概率测度,对基于欧氏距离相关函数的多重分形谱算法的性能进行了分析.采取衬底法与方差法进行仿真比较的方法,进行了线性区间,抗噪声性能和收敛速度的比较.该算法具有保持和加强图像的局部特性,突出图像的细微处的特点,克服了多重分形谱对噪声敏感的缺点,且权重因子收敛快.     

Parallel medical image reconstruction: from graphics processing units (GPU) to Grids

We present and compare a variety of parallelization approaches for a real-world case study on modern parallel and distributed computer architectures. Our case study is a production-quality, time-intensive algorithm for medical image reconstruction used in computer tomography (PET). We parallelize this algorithm for the main kinds of contemporary parallel architectures: shared-memory multiprocessors, distributed-memory clusters, graphics processing units (GPU) using the CUDA framework, the Cell processor and, finally, how various architectures can be accessed in a distributed Grid environment. The main contribution of the paper, besides the parallelization approaches, is their systematic comparison regarding four important criteria: performance, programming comfort, accessibility, and cost-effectiveness. We report results of experiments on particular parallel machines of different architectures that confirm the findings of our systematic comparison.