Image segmentation based on histogram analysis utilizing the cloud model

Both the cloud model and type-2 fuzzy sets deal with the uncertainty of membership which traditional type-1 fuzzy sets do not consider. Type-2 fuzzy sets consider the fuzziness of the membership degrees. The cloud model considers fuzziness, randomness, and the association between them. Based on the cloud model, the paper proposes an image segmentation approach which considers the fuzziness and randomness in histogram analysis. For the proposed method, first, the image histogram is generated. Second, the histogram is transformed into discrete concepts expressed by cloud models. Finally, the image is segmented into corresponding regions based on these cloud models. Segmentation experiments by images with bimodal and multimodal histograms are used to compare the proposed method with some related segmentation methods, including Otsu threshold, type-2 fuzzy threshold, fuzzy C-means clustering, and Gaussian mixture models. The comparison experiments validate the proposed method.     

Platform‐independent profiling in a virtual execution environment

Virtual execution environments, such as the Java virtual machine, promote platform‐independent software development. However, when it comes to analyzing algorithm complexity and performance bottlenecks, available tools focus on platform‐specific metrics, such as the CPU time consumption on a particular system. Other drawbacks of many prevailing profiling tools are high overhead, significant measurement perturbation, as well as reduced portability of profiling tools, which are often implemented in platform‐dependent native code. This article presents a novel profiling approach, which is entirely based on program transformation techniques, in order to build a profiling data structure that provides calling‐context‐sensitive program execution statistics. We explore the use of platform‐independent profiling metrics in order to make the instrumentation entirely portable and to generate reproducible profiles. We implemented these ideas within a Java‐based profiling tool called JP. A significant novelty is that this tool achieves complete bytecode coverage by statically instrumenting the core runtime libraries and dynamically instrumenting the rest of the code. JP provides a small and flexible API to write customized profiling agents in pure Java, which are periodically activated to process the collected profiling information. Performance measurements point out that, despite the presence of dynamic instrumentation, JP causes significantly less overhead than a prevailing tool for the profiling of Java code. Copyright © 2008 John Wiley & Sons, Ltd.     

Global Structure Optimization of Quadrilateral Meshes

We introduce a fully automatic algorithm which optimizes the high‐level structure of a given quadrilateral mesh to achieve a coarser quadrangular base complex. Such a topological optimization is highly desirable, since state‐of‐the‐art quadrangulation techniques lead to meshes which have an appropriate singularity distribution and an anisotropic element alignment, but usually they are still far away from the high‐level structure which is typical for carefully designed meshes manually created by specialists and used e.g. in animation or simulation. In this paper we show that the quality of the high‐level structure is negatively affected by helical configurations within the quadrilateral mesh. Consequently we present an algorithm which detects helices and is able to remove most of them by applying a novel grid preserving simplification operator (GP‐operator) which is guaranteed to maintain an all‐quadrilateral mesh. Additionally it preserves the given singularity distribution and in particular does not introduce new singularities. For each helix we construct a directed graph in which cycles through the start vertex encode operations to remove the corresponding helix. Therefore a simple graph search algorithm can be performed iteratively to remove as many helices as possible and thus improve the high‐level structure in a greedy fashion. We demonstrate the usefulness of our automatic structure optimization technique by showing several examples with varying complexity.     

基于人眼鼻孔特征的眼动跟踪方法

提出了一种基于人眼鼻孔特征跟踪眼动的算法。首先利用Adaboost的层叠式分类器定位人脸、眼睛和鼻子;然后采用梯度Hough变换检测圆的方法精确定位瞳孔虹膜;最后利用几何方法建立椭圆跟踪模型,实现瞳孔的快速跟踪。实验结果表明,该方法定位眼睛嘴角快速准确,同时对眼睛的跟踪具有较好的鲁棒性和实时性。     

Robust stabilization of second-order image-based affine systems

In this paper, the problem of robust relative positioning between a 6-DOF robot camera and an object of interest is considered. Assuming weak perspective camera model and local linear approximation of visible object's surface, an image-based state space representation of robot camera–object interaction model is derived, based on the matrix of 2-D affine transformations. Dynamic extension of the visual model permits to estimate 3-D parameters directly as functions of state variables. The proposed nonlinear robust control law ensures asymptotic stability but at image singularities, assuming exact model and state measurements. In the presence of bounded uncertainties, under appropriate choice of control gains, ultimate boundedness of the state error is also formally proved. Simulation results validate the theoretical framework both in terms of system convergence and control robustness.     

一种自由曲面的快速跟踪求交算法

自由白面的求交算法在ＣＡＤ／ＣＡＭ软件系统中占有重要的地位,并对软件运行的效率有较大的影响。目前常用的Ｂｅｚｉｅｒ曲面分割法难以满足高精度和高速度的要求。为此该文提出了利用交线的几何信息进行快速求交的算法,同时兼顾了快速和高精度两方面的要求,并已在作者自行开发的软件中得到了成功的应用。     

QuadCover - Surface Parameterization using Branched Coverings

We introduce an algorithm for the automatic computation of global parameterizations on arbitrary simplicial 2-manifolds, whose parameter lines are guided by a given frame field, for example, by principal curvature frames. The parameter lines are globally continuous and allow a remeshing of the surface into quadrilaterals. The algorithm converts a given frame field into a single vector field on a branched covering of the 2-manifold and generates an integrable vector field by a Hodge decomposition on the covering space. Except for an optional smoothing and alignment of the initial frame field, the algorithm is fully automatic and generates high quality quadrilateral meshes.     

一种基于主特征的几何空间模糊推理方法

在几何空间中关于几何体之间不确定关系的推理是空间推理技术的主要研究方向,首先,提出了空间几何体的特征与主特征的概念,并证明了几何体特征之间的关系与几何体之间的基本关系的等价性;其次,引入了相邻、平行、从属、同线、线性等空间关系来描述空间几何体主特征之间的关系,并且将这几种空间关系通过隶属度函数模糊化;最后,基于主特征之间的空间关系,提出了一种进行空间模糊推理的方法,并给出了相应的应用实例,表明了所提出的方法是有效的、可行的。