最新刊期
卷 13 ， 期 12 ， 2008
- 摘要：Rate control scheme plays an important role in improving and smoothing the decoding video quality. Over the years, rate control techniques have been studied very intensively for various standards and applications, such as video conferencing with H.261 and H.263, storage media with MPEG1 and MPEG2, and the recent video object coding with MPEG4.This paper firstly described the basis of rate control problem. And secondly classic rate control technology in the standard was introduced. Thirdly we summed up the present techniques as three kinds: rate control technique based on DCT video coder, rate control technique based on wavelet video coder and rate allocation of Fine Granular Scalable video coding. Then we generally discussed and compared the three kinds of methods including the core idea and the advantages and disadvantages of every algorithm of each kind of techniques. Finally, the state of art and possible new directions of rate control were stated.关键词：video transmission;rate distortion;rate control;buffer3551|243|0更新时间：2024-05-07
- 摘要：Developing a reliable face recognition system has been a challenge problem. Infrared appears to be a good alternative imagery as it is independent of external illumination. In this paper we present a survey on Infrared human face recognition, especially on feature extraction. Several major issues for further research are also addressed in this paper.关键词：face recognition;infrared images;feature extraction4137|264|0更新时间：2024-05-07
- 摘要：Study on fast and quantitative reconstruction algorithms for dynamic SPECT(4 dimension) under fan beam geometry is conducted. The correlated information along time axis of projection sequences is decorrelated using Karhune Loève (KL) transformation. Then we reconstruct all or part of the components in KL domain with Novikovs inverse formula, which is deduced for fan beam geometry. The results can be obtained by inverse KL transform. The reconstruction can compensate for the nonuniform attenuation effectively. The results are similar to those from iterative approaches while there construction time is greatly abbreviated. The proposed method can reconstruct 4D SPECT fast and quantitatively and thus has a good future in clinical applications.关键词：nonuniform attenuation;fan beam geometry;Karhune Loève transform;Novikovs inverse formula3110|276|0更新时间：2024-05-07
- 摘要：The regularization method for density reconstruction of axially symmetric objects using a single Xray projection is described. The regularization mathematical model is established according to a prior information of the reconstructed object. The numerical solution can be obtained by solving symmetric positive definite systems of linear equations. Numerical simulation examples illustrate the accuracy of the reconstructed density including edges and values. It has been testified that the regularization method is not sensitive to the measured data noise. This ensures that the small error of measured data will not cause strong oscillation of numerical solution.关键词：tomography;image reconstruction;regularization;algebraic reconstruction technique;Abel inversion3202|223|0更新时间：2024-05-07
- 摘要：In this paper, an adaptive thresholding image denoising method with scale correlation based on the second generation Curvelet transform is proposed. Experiments compare image denoising based on Wavelet and the second generation Curvelet transform. PSNR is used to evaluate the results, and the results show that the method based on the second generation Curvelet transform achieves better denoising than wavelet and simple thresholding methods.关键词：curvelet transform;multiscale geometric analysis;scale correlation3596|246|0更新时间：2024-05-07
- 摘要：Motion estimation (ME) consumes most of the computational resource in a video encoder system. H.264 adopts multimode ME and quarter pel accuracy fractional pixel search, which brings about large scale of computational cost not only to integer pixel ME but also to fractional pixel ME. However, the computational cost of integer pixel ME has been greatly reduced with the development of fast integer search algorithms. Therefore, fast fractional pixel ME algorithms become significantly important for real time applications. A novel fractional pixel motion estimation based on prediction of flat regions of an image is first proposed in this paper. It reduces fractional pel search points efficiently by predicting flat homogeneous regions of the image. Experimental results show that compared to the full fractional pixel search, the proposed method can reduce 22% to 63% of fractional pixel search points while keeping the image quality and compression rate almost unchanged.关键词：H.264;fractional pixel search;multi mode motion estimation;flat region3246|256|0更新时间：2024-05-07
- 摘要：Difference from traditional video surveillance system, panoramic video surveillance system can provide viewers with a complete 360° degrees view. One embedded high resolution panoramic video surveillance system called KDPVS is designed and realized. The paper introduces the multiple camera configuration and video mosaicing algorithm. KDPVS stitches the video data from multiple camera sources into the panoramic video. The system is very convenient for various situations, such as finance system, warehouses, prisons, mobile monitoring, etc, especially useful for indoor monitoring.关键词：panoramic video;embedded system;video mosaicing;video surveillance3355|303|0更新时间：2024-05-07
- 摘要：Based on Generalized Minimal RESidual (GMRES) method and regularization technique, a new image restoration method is presented. The method is based on the Arnoldi process, which yields a sequence of smaller least squares problems to approximate the original ill\|posed problem. Truncated Singular Value Decomposition (TSVD) regularization is used to solve these least squares problems stably. According the characters of image restoration, Lcurve criterion is modified while selecting iteration in TSVD method. Numerical results illustrate good restoration effect.关键词：image restoration;regularization;GMRES;modified L curve criterion3357|248|0更新时间：2024-05-07
- 摘要：An improved homomorphic spatial filtering algorithm is presented. With the reversed low frequency image this algorithm compensates imbalanced illuminating in the uneven brightness image in order to reduce the loss of low frequency components. Then two optimum schemes about spatial filtering are proposed for efficient processing: a method of 2D window template decomposition, which is constructed by tensor production and an approximate spatial filtering based on sampling and interpolation. Simulation indicates that the improved algorithm with the two optimum methods enhances illuminating uniformity, reduces the computational load and keeps the low frequency components effectively. Besides, it can be performed by more 2D windows.关键词：spatial homomorphic filtering;template decomposition;Kronecker product;sampling;interpolation3441|195|0更新时间：2024-05-07
- 摘要：In view of face recognition with only on sample problem, we propose a weighted modular 2DPCA method in this paper. In the method, we first divide original images into modular images and accomplish the sub image 2DPCA feature extraction. Then, we use optical flow between testing and sample image to estimate difference of corresponding pixel blocks quantitatively, which is as criterion for us to give variant weights to each block of difference matrixes between the feature matrixes of sample and that of probing images. Finally, nearest neighbor classifier is employed for classification. The experiment results on the JAFFE and ORL human face database indicate that weighted modular 2DPCA is superior to both conventional 2DPCA and modular 2DPCA in terms of accuracy and robustness with the same dimension of discriminate features, and it is feasible to introduce prior knowledge into PCA method of face recognition.关键词：face recognition one sample problem;modular two dimensional principal component analysis;optical flow3594|254|0更新时间：2024-05-07
- 摘要：Gabor filter responses have successfully used in various important computer vision tasks, such as in texture segmentation, face detection, and iris pattern description. It is evident that Gabor filters have many advantageous or even superior properties for feature extraction. But if the computational complexity cannot be improved their application areas will remain limited. How quickly and accurately using Gabor filter was the identification of the characteristics to become the focus of current research. The paper present Gabor filter envelope based face recognition only the Gaussian part of the filter has to be taken into account; the envelope is similarly the smallest area which includes certain percent of the total filter energy, outside this area can be discarded with only negligible effect in accuracy. The effective envelope is an ellipse which can be encapsulated by a minimal size rectangle. The size of the rectangle may significantly reduce the computational complexity in the spatial domain filtering and save memory in the frequency domain filtering. Experiments using ORL and Yale database indicate that the improved method accuracy outperforms Eigenface and Fisherface algorithm. The new algorithm saves time 20% than traditional methods and gets satisfactory results.关键词：Gabor filters;face detection;Gabor filter envelopes;Eigenface;Fisherface3415|232|0更新时间：2024-05-07
- 摘要：As an effective approach of blind source separation (BSS), independent component analysis (ICA) is a recently developed method in facial expression recognition field, which is used to effectively extract the hidden information of expression images and can improve the rate of expression recognition. Facial expression provides a crucial measure for studies of human emotion, cognitive processes, and social interaction. The key focuses of facial expression recognition are the extraction of expression features and the expression states using features. This paper proposes an expression recognition system based on ICA and hidden markov model (HMM). The system includes two parts: First, it is applied to extraction of expression features using ICA algorithm. In this process it adopts FastICA algorithm in order to increase the speed of feature extraction and its function is prior to primary component analysis (PCA). Second, it is applied to recognizing facial expression using seven HMMs its time efficiency is prior to support vector machine (SVM). Experimental results show that the system increases the whole effectiveness and accuracy of facial expression recognition, and prove that the algorithm is efficient and feasible.关键词：blind source separation;independent component analysis;expression recognition;hidden Markov model(HMM)3268|264|0更新时间：2024-05-07
- 摘要：Gait as a biometric with the unique capability to recognize people at a distance is subject to increasing interest. A gait sequence contains static and dynamic components from the walking way. It is pivotal to integrate them to improve the performance of gait recognition. Initiated from the idea of integration, a moment invariants based scheme for gait recognition is proposed in the paper, taking the magnitudes of the Fourier series coefficients representing moment invariants of gaits as features for identification. The moment invariants describe the static components during the walk, whereas dynamic components are contained in the coefficients extracted according to the whole gait sequence. So firstly, the moment invariants of each frame are computed. Secondly, the moment invariants of humans silhouettes are represented with Fourier series, the Fourier coefficients of which are obtained using a genetic algorithm. Thirdly, the magnitudes of the coefficients are generated as vectors to classify the subjects, which are identified by the kNN classifier. The recognition results of four kinds of gaits in the CMU gait database show that the proposed scheme has a correct recognition rate of more than 80% using a single moment and beyond 90% using jointed moments. Moreover, the scheme is also robust to partial occlusion. The experimental results and performance analysis indicate that the scheme is effective as it integrates static and dynamic components for identification.关键词：gait based recognition;feature extraction;moment invariants;genetic algorithm(GA);KNN classifier2932|243|0更新时间：2024-05-07
- 摘要：With the development of robot and artificial intelligence, the effective recognition and tracking in the complex background becomes a challenging problem，especially in soccer robots game. This paper presents a novel and efficient target tracking algorithm based on a projection method. The projection method has advantages over others. Due to its reduction of calculation work, it makes image processing efficient, and is easy to the implemented. The competition field is divided into several regions from which a seeded point is extracted to be used as a tracer and is traced into a predicting target region. Then the projection of the tracer is calculated along with the vertical (or horizontal) direction in the target region. Based on the projections, a vertex of the target（center for ball）can be recognized. Finally, the position or orientation of the 7 moved targets can be determined. The performance of the proposed method is assessed in the video tracking system. Experimental results are also shown in a computer simulated system.关键词：soccer robots;video tracking;seeded point3657|294|0更新时间：2024-05-07
- 摘要：Wavelet analysis is advantageous in detecting edges. This paper presents a systematic study on V groove welding laser image and the seam recognizing method of multi pass welding image. We propose a seam recognizing algorithm based on wavelet transformation and an algorithm to recognize the corner tracking in a multi pass V groove. According to the characteristic of multi pass V groove, our algorithm outperforms the algorithm of seam recognition in V groove and uses the technology of template matching, can recognize the corner tracking.关键词：edge detecting;wavelet transform;multi pass welding;seam recognition;seam tracking3160|269|0更新时间：2024-05-07
- 摘要：Determining optimum cluster number is a key research topic included in cluster validity, a fundamental unsolved problem in cluster analysis. In order to determine the optimum cluster number, this article proposes a new cluster validity function for two dimensional datasets theoretically based on geometric probability. The function uses of the relationship between a two dimensional dataset and the corresponding two dimensional discrete point set to measure the cluster structure of the dataset according to the distributive feature of the point set in the characteristic space. It is designed from the perspective of intuition and thus can be easily understood. During the process of measurement, the structure information of the point set has been stored in a line segment set generated by connecting each pair points in the point set. The cluster validity function is formed by comparing the values of line segment direction in the line segment set with those resulted from completely random condition. In the case study, it is testified that the pattern of the function curve generated with a given example dataset effectively enables the determination of the optimum cluster number of the dataset and supports the design of cluster algorithms.关键词：Cluster validity;Geometric probability;cluster analysis;The optimum cluster number2983|225|0更新时间：2024-05-07
- 摘要：In order to reduce matching error, in this paper, a new matching method for particle images is proposed based on the SOM neural network, which combines the nearest neighbor matching algorithm with the cross correlation algorithm. Firstly, the cross correlation approach is used to evaluate the initial matching position. Secondly, the processing results of the correlation are used to build the neural network. Thirdly, nearest neighbor matching algorithm is adopted to select the best matching points. The modified method can reduce the number of false vectors and improve the practical value. At last, the synthetic particle images and real particle images are tested and the errors are analyzed. The experimental results show that the proposed method is a robust algorithm for measuring the movement of particles and the vector fields can be obtained with high precision.关键词：image matching;SOM neural network;particle image velocimetry;correlation technology;robustness2892|209|0更新时间：2024-05-07
- 摘要：The 3D information of an object can not be obtained using the conventional computed tomography when the object is notfit for rotating scan in digital radiography (DR) inspection. So, stereo vision is a better solution. Stereo matching is an important research area in stereovision. Although stereo matching research has progressed remarkably, the studies are mostly aiming at reflection imaging field, such as visible light, and transmission imaging field, such as X ray. For the dissimilarity of imaging principle, the stereo matching technique of transmission images is different from that of reflection images. In the paper, the stereo matching technique for X ray images are studied in detail. Edge is advised to be used as matching primitive. According to the characters of X ray images, the constraints of stereo matching are set up. The reasons of matching uncertainty are analyzed. Finally, the “coarse to fine” strategy is suggested and the constraint from multi view images is used to implement fine matching. Finally, to validate the technique, digital radiography system with intensifier is used to imaging for a standard sample. The experimental results show that the technique is feasible.关键词：stereo matching;matching primitive;constraint;uncertainty2685|250|0更新时间：2024-05-07
- 摘要：Image mosaic is a problem inevitable faced in reconstruction for facade texture from close range digital imagery. The approach of automatic mosaic for building facade texture from close range digital imagery is studied in this paper. When the camera is distant from building and the images are taken along a linear route, after the rectification process, only mosaic point pair is acquired to implement mosaic process. However, this approach wont be applicable when the imagery is taken too close to the facade, since the geometric distortion cannot be eliminated perfectly after rectification process. Therefore, strip method, similar to strip block adjustment, is presented to generate the whole facade texture. Two refining strategies are presented to optimize the mosaic result. One is to refine mosaic region by constraining correspondingly horizontal lines. The other is to refine by choosing more corresponding points according to the relative spatial relationship of the image sequence. Experiments are carried out on ground leveled image sequences. It is proved that seamless mosaic is realized by the method presented because the geometric distortion between each image is eliminated perfectly.关键词：facade texture;automatic mosaic;projective difference;constraint of correspondingly horizontal lines;strip method2739|247|0更新时间：2024-05-07
- 摘要：Curvelet, as a new multi scale analysis algorithm, is more suitable for image processing than wavelet,and is more appropriate for the analysis of the image edges such as curve and line characteristics. In addition, the representation contains more directional information. In this paper the theory and implementation of the second generation Curvelet transform is reviewed. The methods of remote sensing image fusion are proposed based on Curvelet transform and the scheme using Curvelet and IHS transform is described in detail. The processing of fusion is performed with the high resolution panchromatic and low resolution multispectral remote sensing images. The result of experiment indicates that the performance of Curvelet based image fusion method excels those of based IHS or wavelet transform. When the Curvelet transform is introduced to image fusion,original images are characterized better and more information for fusion is obtained.It not only preserves spectral information of the original multispectral image well,but also enhances spatial information with more datails.关键词：remote sensing image fusion;curvelet transform;IHS transform;wavelet3086|230|0更新时间：2024-05-07
- 摘要：Mesh surface parameterization is an important problem in Digital Geometry Processing, and triangular mesh is the typical form for mesh representation. To solve the problem of planar parameterization for triangular mesh fast, and minimize the distortion of triangles generated in the parameterization simultaneously, a simple as similar as possible planar parameterization method for triangular mesh is presented in this paper. The angles and length ratios between two adjacent edges are globally preserved in a least squares sense after the parameterization, by which the similarity of the corresponding triangles can be satisfied. A linear system is constructed according to the corresponding angle and length ratio of two adjacent edges on the triangular mesh, and the planar parameterization result can be fast obtained by solving the sparse linear system with some initial conditions. Linear constraints can be combined into the linear system in our approach, and the algorithm is of linear complexity. This method has a direct geometric interpretation and can be implemented more easily than other methods. Experimental examples show that good planar parameterization results can be derived from this method, which is a very efficient tool for the applications in Computer Graphics, such as texture mapping.关键词：digital geometry processing;mesh parameterization;as similar as possible;texture mapping3318|243|0更新时间：2024-05-07
- 摘要：Road networks’ auto selecting is important but difficult in auto generalization. All roads in the map have’t been regarded as whole in present selecting methods. So the characteristic of road networks can’t be kept. A series of experiments have been done that road networks have been auto selected by different methods using graph theory. The results have been analyzed and compared, and then a better method has been proposed for road selecting. Through these experiments, the effect is better and it fits the necessity of road networks auto generalization.关键词：road networks;automatic map generalization;selection operator;graph theory3083|212|0更新时间：2024-05-07
- 摘要：A tetrahedral mesh generation method based on which the mesh density could be adjusted with the shape of the object was developed in the paper. The BCC lattice was used to initialize the mesh space. According to the curvature and the distance from the lattice to the surface of the object, the LEPP algorithm is adopted to refine the initialized mesh from the outer to the inner with different scales. Then all the lattices that stride the surface were adjusted to fit the shape of the object. At last the quality function navigated Laplacian smoothing and Edge Collapse methods were used to optimize the quality of the meshed tetrahedral and the meshed model was obtained. Result shows the method improves the configuration of the mesh while the quality of the tetrahedral is also guaranteed. The method is tested to be useful in the finite element modeling based on 3D computer tomography images or surface model.关键词：mesh generation;mesh optimization;finite element modeling3352|210|0更新时间：2024-05-07
- 摘要：In computer graphics, spatial analysis of geographic information system (GIS) and computer aided design (CAD), a fundamental problem is to compute the minimal distance of two polygons. An efficient algorithm is presented for computing the minimal distance between two polygons based on the triangulation of their association polygon. The main idea of the algorithm is that two polygons were linked by an association polygon constructed, so that the minimal distance between two polygons is restricted within the association polygon. According to three different relationships between two polygon boxes, the approach of constructing the association polygon is described in detail and the association polygon is proved to be a simple polygon. The association polygon is triangulated to find the minimal distance. As a result, the distance between a vertex and an edge within one or two adjacent triangles is the minimum. The time complexity of the algorithm is linear related to the size of the two polygons.关键词：association polygon;minimum bound rectangle(MBR);triangulation3234|239|0更新时间：2024-05-07
- 摘要：To achieve efficient data transfer in real time fly geometric environment (FGE), uniform data organization for massive raster and vector data in the FGE is demanded. In uniform data organization, the rectangular blocking organization is used to deal with massive raster and vector data. To efficiently organize data with rectangular block for vector data needs efficient clipping algorithm using rectangular clipping window. Sutherland Hodgeman method and Maillot method are this kind of polygon clipping algorithms using rectangular clipping window. But Sutherland Hodgeman method and Maillot method can not get the correct clipping results if the number of the separate parts in the result polygon is more than one. Weiler Atherton method, Vatti method and Greiner Hormann method can get the correct clipping results in this case. Greiner Hormann method has the best performance in time and space consuming comparing with Weiler Atherton method and Vatti method. A new fast polygon clipping method using rectangular clipping window is proposed in this paper. The advantage that Weiler Atherton method, Vatti method and Greiner Hormann method use linking to form the result polygon has been used as reference in the new method. The new method also improves the mode that Greiner Hormann method used to insert the cross points. Furthermore, about the data structure, the new method uses the single directional linked list that is simpler than the bidirectional linked list used by Greiner Hormann method. The experimental results show that the new method can obtain correct clipping result and it has less time and space consumption comparing with Greiner Hormann method.关键词：vector data;data organization;polygon clipping4372|393|0更新时间：2024-05-07
- 摘要：Speckle is the fundamental uncertainty factor in laser triangulation. A method to simulate the speckle in rotationally symmetric triangulation was presented and the simulated image was obtained. In this kind of triangulation sensors, the incident laser point will be imaged to a ring on the detector and the speckle is accordingly arc shaped. Properties of this kind of speckle were studied. The speckle size in radius direction of the ring obeyed the subjective speckle, and is determined by the number aperture of the optical system. In tangent direction of the ring, the speckle is essentially an objective speckle, its size is determined by the optical path length from the object to the detector, the area of the incident laser spot, as well as the radius of the imaged ring because of optical path was folded. Experiments showed that the simulation result was coincident with speckle theory. Based on the simulation, an analysis of the uncertainty limits of rotationally symmetric triangulation sensor was given. It shows that using the optical layout in our sensor, an uncertainty about 1/5 of traditional triangulation was estimated with same optical system numerical aperture and grey centroid algorithm.关键词：optical measurement;laser triangulation sensor;speckle;simulation;rotationally symmetric3354|214|0更新时间：2024-05-07
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