最新刊期
卷 6 ， 期 6 ， 2001
- 摘要：This paper is the literature bibliography on computer graphics in China in 2000. Graphics engineering is an inter|subject on studying graphical theory, graphical techniques and graphical application. Its research content covers almost all aspects of the human life, including industry,visualization,education,entertainment,et al. In the early beginning of 1990's, some new graphics techniques are derived from traditional computer graphics,they are virtual reality, visualization, physical based simulation. Based on the current status of the research on graphics engineering as well as the distribution of related pulications in China, we began this literature overview work from 1996, we collected and classified most of important papers in computer graphics field in every year,hoping to give an overview image of the whole research work performed in China. This year we selected about 304 references from 11 important Chinese journals published in 2000 and classified these referneces into different categories according to their contents. We hope that the paper could provide readers with a general and up|to|date overview of graphics engineering in China.2715|402|0更新时间：2024-05-07
- 摘要：Picture quality evaluation methods could be utilized to assess image algorithms' performance. The evaluation of image quality includes subjective evaluation and objective test. The traditional subjective evaluation depends on observer's experiences and motivations, and therefore it is complex and its results always change. With the development of the video compression technology, it is very urgent to research new video quality evaluation method. The key point of the video quality evaluation is that its model should match the perceptive characteristics of human. Based on the visual acuity, contrast sensitivity function, multi channel structure and masking effect, this paper summarizes main properties of Human Visual System (HVS) taken into account in the assessment of the video quality. It also presents several comparatively satisfactory video quality models based on HVS, including spatio temporal model, RAI model, three dimension weighted signal to noise model and three layered bottom up noise weighting model. Their performances are also analyzed respectively. The perspective of video quality evaluation is given finally.2829|566|0更新时间：2024-05-07
- 摘要：Image compression based on Lossless Region of Interest (ROI) means to compress interesting regions in an image without loss, and to compress uninteresting regions with a little loss. Based on this idea a high compression ratio can be obtained and the important information can be preserved losslessly. In this paper, the near lossless image compression is implemented, based on Integer Wavelet Transform(IWT) and embed zero tree coding scheme. In addition, the tree mapping shape coding scheme is proposed. In this paper the IWT and embed zero tree coding scheme are introduced simply, then the tree mapping shape coding algorithm are presented in detail, finally the experimental results are presented and compared with the results of lossless compression. Experimental results represent that the algorithm can obtain much higher compression ratio than lossless compression algorithms, but the improvement of compression ratio is related to the size of ROI and quality of uninteresting regions.2458|467|0更新时间：2024-05-07
- 摘要：A new median-based filtering algorithm—extremum median filtering is presented. In order not to perturb the efficient signals as much as possible when the noises are removed, the following approaches are developed in this paper. First, all the pixels are separated into signal pixels and noise pixels according to the decision criterion given in the following; then, noise pixels are replaced with the median value of their neighborhood in the input image. The decision criterion: if a pixel value is the extremum (max or min) of its neighborhood, it is a noise pixel; else, it is a signal pixel. This decision criterion is under such an assumption: inherent relationships exist among neighbor pixels. If a pixel value is far higher or lower than the others' value of its neighborhood are, that is to say, a pixel has lower correlation with its neighbors, we may consider that it had\nbeen contaminated with noise. Else, if it is similar to the others, we consider that it represents an effective signal. Experimental results show that the assumption fits the facts quit well.In this paper, attention is forcused on filtering of images degraded by“salt and pepper”noises. Examples on images containing 184×148 pixels are given.Experimental results show that the EM filtering has better performance than standard median filtering with less subtle details being eliminated. The SNR of the image filtered with EM filter is about 4dB higher than that with median filter. This is because the operation only affects noise pixels and most of the uncontaminated pixels keep intact. Especially,in the case of lower SNR,larger filtering window improves the SNR notably. Median filter is not the case, for the filtering operation blurs the image extremely with the increasing of the filtering window.5214|780|0更新时间：2024-05-07
- 摘要：A classification model for remote sensing imaging is presented. The Extended self similar model(ESS)is a general fractional Brownian motion(fBm) model. Its multiscale Hurst parameters have relations with roughness. At the meantime, it doesn't require the roughness to be scale|invariant as fractal dimensions do. The ESS is closer to the realities than fBm. Moreover, ESS gives multiscale parameters to provide more accurate interpretation of textures while the fBH gives only one. The multiscale Hurst parameters can discriminate a large number of natural textures and are suitable to be the features for texture classification. These features' dimension is lower compared with many other texture features, so that the computation intensity is less. Directed Hurst parameters describe the roughness at four orientations and multiscales. In this study they are mixed with the mean and standard deviation of gray level to be the feature vector. A new classification model of mixed multiscale Hurst parameters is constructed based on Bayes theorem. In this model we suppose that the conditional possibility distribution function of each feature is Gaussian, and the features are independent with each other. The a priori possibilities are decided by the highest rate of correct classification of the training set. For remote sensing texture classification, the performance of the new model is compared to other features, such as co occurrence matrix features and Kaplan's features, etc. These classification algorithms are all based on Bayes theorem and the assumption that the a priori possibilities of all the classes are equal. Our experiments show that higher rate of correct classification to SPOT image is obtained by this new model.2509|406|0更新时间：2024-05-07
- 摘要：In this paper, a new low bit rate image compression algorithm based on wavelet zero tree image coding scheme is put forward. The coefficients in the horizontal and vertical orientation sub images of all scales are reordered by the means of the transform because there are many big energy coefficients. The target of doing so is to produce new tree structure, to add the number of zero tree. And the significant wavelet coefficients in these sub images are concentrated in the low frequency area of the corresponding subbands. So the energy of these sub images is concentrated in the area of the corresponding left hand, and the con centration property of the new trees is good, and it can improve the encoding efficiency effectively. It also can improve the transmission rate of the significant coefficients. The results of the reconstruction images are good. And bit allocation is optimized and the peak signal to noise ratio ( PSNR ) of the reconstructed image is improved compared to embedded zero tree wavelet encoding(EZW) algorithm at the same bit ratio.2420|483|0更新时间：2024-05-07
- 摘要：s How to get pattern elements is a bottle neck problem all the while in the computer aided pattern design system. Firstly, this paper introduces the principle of synthetic reasoning and defines its three components:synthetic source S, synthetic constraint C, synthetic result R. Secondly, it discusses a way of the pattern element transformation and generation based on the synthetic reasoning. Thirdly, based on eigenvector, this paper present the pattern element generation model with very simple field strength function of components. Because this model is simple, intuitional and coincident with the data structure of synthetic source and result, the implementation is relatively easy and the effect is fairly good. Then some examples are presented. Finally, this paper proposes some evaluation and some suggestion about advanced research in the future. On all accounts, this method can use the visual information of acquired pattern elements, under some special requests, to produce new ones rapidly or transform them to other conformations, which will amplify greatly the resource of pattern elements and resolve forenamed problem at a certain extent.1974|392|0更新时间：2024-05-07
- 摘要：This paper present a novel easy and effective algorithm to plant digital watermark into digital images, this algorithm is different to general watermarking methods based on spread spectrum, because a new orthogonal base based on piecewise polynomial is constructed. The watermark based on this algorithm can resist energy loss caused by lose compression of digital image. In the first part of this pper, piecewise linear U system and its properties will be introduced respectively, corresponding graphs are shown, too. Following this part, how to generalize this algorithm to piecewise k degree U system is discussed; In the third part fo this paper, based on decompose digital image by piecewise linear U system, a kind of digital image watermarking scheme will be provided, the process of this algorithm is introduced step by step. By the end of this paper, some corresponding experimental results based on U system will be listed. The experimental results demonstrate the algorithm is reliable.2142|442|0更新时间：2024-05-07
- 摘要：In this paper, we proposed a new general additive watermarking model based on the content of digital images, called as CBWM (Content Based Watermarking Model). It provides a common basis to study many existing watermarking algorithms that are based on unitary transforms and to evaluate their performance and characteristics. CBWM is designed to address two important issues of digital watermarking. One is the requirement of robustness. In order to improve robustness and security, the embedded watermark is designed to be orthogonal to the feature vector of the original image, which means that watermarking casting is image content dependent. The second issue is watermark detection. CBWM presents a statistical approach to watermark detection based on the Neymann Pearson criterion and describes a method for computing the probability of false alarm and missing rejection during watermark detection. In experimental tests, CBWM is applied to the popular discrete cosine transform and promising results are obtained.2423|452|0更新时间：2024-05-07
- 摘要：Geometric constraint solving has applications in a wide variety of fields, such as mechanical engineering, chemical molecular conformation, geometric theorem proving, and surveying. There are mainly three approaches to geometric constraint solving: numerical approach, symbolic approach and constructive approach. Since the constructive approach are simple and practicable, most parametric design take the constructive approach as the basic approach. In the light of the shortage of using only line and circle (rule and compass) as basic drawing tools in constructive approach, in this paper, we introduce a class of new drawing tools: conics. We prove that the class of diagrams within the drawing scope of this new tool is larger than that can be drawn with line and circle. Actually, we prove that a diagram can be drawn with conics if and only if this diagram can be described with a sequence of triangulated equations of degree less than or equal to four. This allows us to maintain the elegance of geometric constraint solving with ruler and compass, because the solutions of cubic and quartic equations can be written explicitly with radicals.2870|495|0更新时间：2024-05-07
- 摘要：Many knot spline interpolating curves (MSIC) are a kind of spline curves that precisely pass through every interpolating point on the curves, many knot spline interpolating surfaces (MSIS) also pass through every interpolating point on the surfaces. Many knot spline interpolating curves have been successful applied in many fields, such as computer animation, computer font design and wavelet analysis, etc. Based on studying of many knot spline interpolating curves, some definitions and properties of rational many knot spline interpolating curves and those of rational many knot spline interpolating surfaces are taken into account in this paper. All the concepts and properties discussed in this paper are the first step to research rational many knot spline interpolating curves and rationl many knote interpolating surfaces. Following the properties and definations, some applications of these rational curves and surfaces are introduced. The Problem of continuity of many knot spline interpolating curves and that of rational many knot spline interpolating curves are discussed by the end of this paper.2791|426|0更新时间：2024-05-07
- 摘要：Curve modeling on curved surface is paid much more attention recently because of its wide application in industry, which include fiber weaving, 3D garment clipping design and composite material product design. Computer aided design for filament winding is a basic technique in the area of production of composite materials. Torus is a typical product made of composite material; they are used as tube joints widely in chemistry and oil industry. The manufacture of torus is usually by means of filament winding. The main step for filament winding is fiber path design. The design of fiber path on torus is main topic of this paper. In the first part of the paper, the fiber path is designed as geodesics, the solution to the geodesics on a torus is discussed; in the second part of the paper, a formula for computing the semi geodesics on a torus is derived, a numerical calculation for semi geodesics from the formula is analyzed in detail. Lastly, the method is applied in a practical example.2582|457|0更新时间：2024-05-07
- 摘要：In this paper, firstly the distribution characteristic of accumulate granule on the image gray space is analyzed under the different angles and distributions of light ray, the foundation is provided for abstracting granule contour information. A non-supervisory roof edge detection method is proposed based on a logic judgement, which includes four steps:(1) The analysis window consisting of 3×3 sub-windows is assumed, where each sub-window consist ofl×lpixels, the size of sub-window is related to the size of objects. (2) The gray average value of 3×3 sub-windows is calculated. (3) The gray average values of 3×3 sub-windows is compared respectively along four directions, if the gray average value of center sub-window is smaller than one of other two sub-windows in some direction, the center or some near center pixel in the sub-window is labeled as the candidate of edge pixel. (4) Scanning original image get the edge bit-map by the analysis window. (5) The false edge pixels in the bit-map can be removed by the proposed false edge filtering method. This method need not to the conventional procedure of abstracting edge pixels through calculating edge intensity and then thresolding edge intensity, is suited to the roof edge detection. The experiment results of the granule contour abstraction in accumulate global granule image proved that the method is effective.2250|386|0更新时间：2024-05-07
- 摘要：Design is an important branch in Computer Aided Design. The automatic dimensioning in engineering draft of steelworks could improve the efficiency of the plant disign. During the developing steelworks design software, a practical algorithm to generate the dimensions on an engineering draft describing specific parts of the steel structure. As for a general engineering draft, the variety of part shapes, the complexity of illustration contents, the abnormality of layout and technical limitations make the automatic dimensioning seem too difficult to be realized. So a special algorithm to dimension joint draft in steelworks draft is proposed. This approach divides the margin of joint draft into eight zones:left top dimensioning zone,left dimensioning zone,left bottom dimensioning zone,top dimensioning zone etc. At the same time, a leader dimensioning algorithm is proposed. These approaches are feasible to generate the ordered dimensioning items for the disordered draft drawings. The algorithms have been applied in the PDSOFT Steelworks successfully.2813|557|0更新时间：2024-05-07
- 摘要：Bring forward the concept of realizing virtual environment based on software ;Illuminate the differences between virtual reality and simulation by comparing modes of interaction;Implement method to model virtual circumstance by 3D Modeling and rendering ,Illuminate the steps to build virtual scene with model based method: Describe the frame of object with geometry principle, Add material and light to the frame, Render it to virtual scene which look like reality;Advance the method to improve the real time of virtual scene, In order to make scenes more efficiently rendered, Combine levels of details with fuzzy math , Display the objects in different distance at different levels of detail: Render object in far distance in low details, Render closer object in fuller details. Using virtual and enhanced reality technology, Combine image and model to improve real time: Take pictures of the static object such as background, Construct the virtual static scene with texture mapping technology, Immerge the objects modeled to be manipulated in the virtual static scene, Merge modeling based method into image based method to improve real time of interaction.2317|447|0更新时间：2024-05-07
- 摘要：The traditional two dimensions express method of geographic information system can't meet the need of people, especially for city planer. The 3D building models can recover city construction environment, and finish querying, measuring, cruising et al jobs. It is signify in city geography information system. VRML technology can building dynamic, reality, senseful virtual environment and it don't limit to the bound of field, is an efficient tool for analysis city scene. In this paper we use maximum bound box method to merge 3D building model and 2 5D DEM at first, then use Meier relate data structural to represent topology and semantic information in geometry model and realized dynamic display through the VRML browser to finish the job of using regular 2D GIS data to construct 3D building virtual reality model. The last experiment results show that our method can dynamic display 3D building model at different viewpoint?scale and view angle in VRML browser and realized stereoscopic viewing on the computer screen. Based on experiment and analyzing, we can draw the conclusion that the condition of building 3D building model is provided with the mature development of 2D GIS.2914|498|0更新时间：2024-05-07
- 摘要：In the application of remote multimedia surveillance based on PSTN(Public Switching Telephone Network), one of the key technologies is the compression of video and speech data stream at a ratio as high as possible, while the quality of the video and speech are ensured for the surveillance application; Other key technologies are such as the real time processing of the compression of video and speech data stream. The PSTN based remote multimedia surveillance system, which is introduced in the article, compresses the video data stream based on the protocol H 263 and speech data stream based on the protocol G 723 1. The article first introduces the architecture of the system. Then after a short introduction to the H 263 and G 723 1 protocols based video and speech compression algorithms, some considerations with the video and speech compression are discussed for the requirements of the remote multimedia surveillance application. Further, the design and realization of the remote surveillance terminal, which is the key part of the system, are introduced with details. Also the key technology and method of the real time processing of speech and video compression based on DSP(Digital Signal Processor) are presented. As a conclusion, the main performances of the system are reported at the end of the article.2519|471|0更新时间：2024-05-07
- 摘要：With the popularity of the application of computer and network technology, there is a bright prospect for the multimedia video terminal embedded in PC. But because of the speed limit of current computer, this terminal could not be realized with software fully. According to this condition, we analyses the computation of video codec in detail, and present a design idea for multimedia terminal based on the cooperation of software and hardware. With this idea, a multimedia video terminal is designed with a video microprocessor which is used for low level codec computation, such as DCT/IDCT, ME/MC, and Quantization/Inverse Quantization ,and PC is used for processing medium and high level task such as VLC/VLD, the construction and deconstruction of coded stream . So it takes each advantage of them fully, and not only enhances the global performance greatly, but also provides more functions. This also indicates a more economic way for MPEG2 encoder realization too.2182|444|0更新时间：2024-05-07
- 摘要：With the development of CSCW techniques, applying cooperative design methods into conceptual design is a hot and interesting research project in product design area now. Layout design and ergonomics design are two sub processes of conceptual design which affect and restrict each other. Function face is a significant concept in the area of industrial design. It is classified as physical function face and physiological and psychological function face. Function face can be used to characterize the relationships of the product components and the human. In order to cooperate layout design and ergonomics design, the function face is adopted as the basis to distribute the conceptual design tasks, and the function face based cooperative design process and method are put forward. According to the characters of layout design and ergonomics design, a description method of computer supported cooperative design model is introduced. This design model can suit the changes in cooperative design. Finally, an applicable scheme of the computer supported layout ergonomics cooperative design system in motorcycle design is described. This system is based on Client/Server mode and consists of a layout design client, an ergonomics client and a cooperation server.2160|496|0更新时间：2024-05-07
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