共查询到20条相似文献，搜索用时 843 毫秒
1.
A non-local denoising (NLD) algorithm for point-sampled surfaces (PSSs) is presented based on similarities, including geometry intensity and features of sample points. By using the trilateral filtering operator, the differential signal of each sample point is determined and called "geometry intensity". Based on covariance analysis, a regular grid of geometry intensity of a sample point is constructed, and the geometry-intensity similarity of two points is measured according to their grids. Based on mean shift clustering, the PSSs are clustered in terms of the local geometry-features similarity. The smoothed geometry intensity, i.e., offset distance, of the sample point is estimated according to the two similarities. Using the resulting intensity, the noise component from PSSs is finally removed by adjusting the position of each sample point along its own normal direction. Experimental results demonstrate that the algorithm is robust and can produce a more accurate denoising result while having better feature preservation. 相似文献
2.
Non-local means(NLM)method is a state-of-the-art denoising algorithm, which replaces each pixel with a weighted average of all the pixels in the image. However, the huge computational complexity makes it impractical for real applications. Thus, a fast non-local means algorithm based on Krawtchouk moments is proposed to improve the denoising performance and reduce the computing time. Krawtchouk moments of each image patch are calculated and used in the subsequent similarity measure in order to perform a weighted averaging. Instead of computing the Euclidean distance of two image patches, the similarity measure is obtained by low-order Krawtchouk moments, which can reduce a lot of computational complexity. Since Krawtchouk moments can extract local features and have a good antinoise ability, they can classify the useful information out of noise and provide an accurate similarity measure. Detailed experiments demonstrate that the proposed method outperforms the original NLM method and other moment-based methods according to a comprehensive consideration on subjective visual quality, method noise, peak signal to noise ratio(PSNR), structural similarity(SSIM) index and computing time. Most importantly, the proposed method is around 35 times faster than the original NLM method. 相似文献
3.
The problem of computing a piecewise linear approximation to a surface from its sample has been a focus of research in geometry modeling and graphics due to its widespread applications in computer aided design. In this paper, we give a new algorithm, to be called offset surface filtering (OSF) algorithm, which computes a piecewise-linear approximation of a smooth surface from a finite set of cloud points. The algorithm has two main stages. First, the surface normal on every point is estimated by the least squares best fitting plane method. Second, we construct a restricted Delaunay triangulation, which is a tubular neighborhood of the surface defined by two offset surfaces. The algorithm is simple and robust. We describe an implementation of it and show example outputs. 相似文献
4.
提出基于动态时间弯曲技术的流数据处理方法,将一段时间内采集到的流数据作为一个时间序列来进行处理．由于同一时间段内数据流变化的影响因素基本相同,导致一些数据流变化存在错位相似,具体表现为数据流形状大致相同,但在时间上有所超前或延迟．对于这种错位相似的数据流采用常用的欧几里得测度法是无法识别的,而采用动态时间弯曲技术却可以很好地判断数据流的这种相似性．在采用动态时间弯曲路径法得到两个时间序列对应点的基础上提出了用预测法估计两个时间序列的关系,从而确定时间序列最佳匹配点的算法． 相似文献
5.
主流形和非线性维数化简的切向空间校正 总被引：8，自引：0，他引：8
We present a new algorithm for manifold learning and nonlinear dimensionality reduction. Based on a set of unorganized da-ta points sampled with noise from a parameterized manifold, the local geometry of the manifold is learned by constructing an approxi-mation for the tangent space at each point, and those tangent spaces are then aligned to give the global coordinates of the data pointswith respect to the underlying manifold. We also present an error analysis of our algorithm showing that reconstruction errors can bequite small in some cases. We illustrate our algorithm using curves and surfaces both in 2D/3D Euclidean spaces and higher dimension-al Euclidean spaces. We also address several theoretical and algorithmic issues for further research and improvements. 相似文献
6.
We present a new algorithm for manifold learning and nonlinear dimensionality reduction. Based on a set of unorganized data
points sampled with noise from a parameterized manifold, the local geometry of the manifold is learned by constructing an
approximation for the tangent space at each point, and those tangent spaces are then aligned to give the global coordinates
of the data points with respect to the underlying manifold. We also present an error analysis of our algorithm showing that
reconstruction errors can be quite small in some cases. We illustrate our algorithm using curves and surfaces both in 2D/3D
Euclidean spaces and higher dimensional Euclidean spaces. We also address several theoretical and algorithmic issues for further
research and improvements.
Project supported in part by the Special Funds for Major State Basic Research Projects (Grant No. G19990328) and Foundation
for University Key Teacher by the Ministry of Education(Grant No.CCR-9901986) 相似文献
7.
提出一种基于薄板样条的遥感影像非刚性配准方法。首先,根据SIFT算法分别在参考影像与待配准影像中提取特征点;然后,对特征点进行匹配,并利用RANSAC一致性分级检验方法,由粗至精分级排除错误匹配点;最后,利用同名匹配点构建薄板样条配准模型,并完成图像配准结果。实验结果表明,文中方法能有效解决遥感影像在时相变化、几何变形等条件下的配准,具有较高的实用性。 相似文献
8.
某一种去噪方法通常只对某一类噪声的滤除较为有效,为了抑制混合噪声,提出一种结合中值滤波与小波去噪的图像去噪算法.该算法首先检测出脉冲噪声点,并采用自适应窗口对脉冲噪声点进行中值滤波处理,然后用基于高斯混合模型的小波去噪法滤除图像中的高斯白噪声.仿真实验表明,对于被高斯、脉冲混合噪声污染的图像,该算法的去噪效果显然比单一的中值滤波和小波去噪法好得多. 相似文献
9.
Recently a new clustering algorithm called ＇affinity propagation＇ （AP） has been proposed, which efficiently clustered sparsely related data by passing messages between data points. However, we want to cluster large scale data where the similarities are not sparse in many cases. This paper presents two variants of AP for grouping large scale data with a dense similarity matrix. The local approach is partition affinity propagation （PAP） and the global method is landmark affinity propagation （LAP）. PAP passes messages in the subsets of data first and then merges them as the number of initial step of iterations; it can effectively reduce the number of iterations of clustering. LAP passes messages between the landmark data points first and then clusters non-landmark data points; it is a large global approximation method to speed up clustering. Experiments are conducted on many datasets, such as random data points, manifold subspaces, images of faces and Chinese calligraphy, and the results demonstrate that the two approaches are feasible and practicable. 相似文献
10.
利用Galileo变换,建立了Galileo几何.讨论了Galileo平面几何中的距离,直线间的交角问题以及Galileo平面上三角形的一些性质. 相似文献
11.
利用编码元和非编码元,根据标记点的尺寸、形状及灰度变化等特征提取目标,然后利用非编码元与编码元的不同形状与灰度特征,提出一种改进的编码元自动身份识别方法,同时实现非编码元与编码元的分类;并利用质心定位方法抽取标记点中心位置,抽取的中心具有亚像素级.在利用编码元的身份信息实现同名编码元匹配的基础上,由相似性和相容性确定非编码元的初始匹配,通过3个准则从非编码元的初始匹配中剔除误匹配,最终得到同名非编码元的匹配结果.经实验验证,该算法速度快、匹配率高、鲁棒性好. 相似文献
12.
基于最优小波包基的信号去噪方法研究 总被引：1，自引：0，他引：1
冯宏亮 《西安文理学院学报》2009,12(2):60-63
改进了基于最优小波包基的信号去噪算法,该算法以小波包分析为基础,根据最小代价原理搜索信号分解的最优基,然后对高频和低频系数采用不同的阈值算法进行量化,用量化后的系数重构得到去噪后的信号． 相似文献
13.
利用有限域上辛几何、酉几何及正交几何的几种类型的子空间构作了若干个Cartesian认证码,计算了它们的参数.假设编码规则按照一种均匀概率分布选择,那么假冒攻击成功的概率PI和替换攻击成功的概率PS也被计算. 相似文献
14.
在图像拼接技术中,单应性矩阵是实现两幅图像正确拼接的关键因素。针对传统RANSAC算法误匹配点概率较高,需要设置固定的投影误差阈值t导致迭代次数多、运行时间长、估计的单应性矩阵精度低等问题,提出一种改进的RANSAC算法以降低误匹配率。利用特征点周围灰度梯度相似性,剔除初始匹配中部分误匹配点,以减少矩阵估计的迭代次数;通过快速舍弃错误的单应性矩阵以减少内点检测时间,提高算法运行效率;通过BGD算法最小化损失函数以拟合精确的单应性矩阵。对比实验结果表明,改进的RANSAC算法能够有效剔除误匹配点,减少内点检测时间,提高单应性矩阵H的精度。 相似文献
15.
LIU Guang-hui CHEN Chuan-bo 《浙江大学学报(A卷英文版)》2007,8(8):1210-1217
When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster. 相似文献
16.
射影几何中抛物线的若干问题 总被引：1，自引：0，他引：1
杨俊林 《内江师范学院学报》2009,24(2):20-22
在射影几何中,作为二级曲线的抛物线可以看作由定点与定直线上的动点连线的中垂线构成．二阶曲线若存在一个外切三角形,其外接圆过二阶曲线的焦点,则该二阶曲线为抛物线．过定点的二阶曲线的三条弦,若每条弦的两端点处切线正交,则二阶曲线为抛物线．给定三角形外接圆上任一点（不是顶点）,存在唯一抛物线以给定点为焦点,与已知三角形三边相切． 相似文献
17.
曲面柔性制孔机器人末端执行器及其法向姿态调整的一种新算法(英文) 总被引：1，自引：0，他引：1
设计了一种曲面柔性制孔机器人末端执行器,并针对该末端执行器提出了一种法向姿态调整的新算法.空间不共面四点可以确定一个与之相切的球面,求出该球面的半径及球心位置,以该球面近似代表制孔点区域的曲面,联结制孔点与该球面球心的矢量即可近似代表制孔点曲面的法矢量.根据这一原理,该算法首先用4个位移传感器测量出曲面上制孔区域内4个点的坐标,并由此计算出制孔位置的法向矢量,然后计算出此法向矢量与末端执行器上电主轴的轴线矢量的误差.根据该误差,进一步计算出末端执行器上2个旋转轴的旋转角度及制孔机器人另外3个直线移动方向的移动距离,从而实现调整主轴在制孔点与曲面垂直的功能.针对2种类型曲面的仿真结果表明,根据该算法可以实现较高的调整精度和效率. 相似文献
18.
利用偶特征的有限域上正交几何构造了一类Cartesian认证码,详细地计算了其参数。对于有限域上典型群的其它几何(辛几何、酉几何及奇特征的正交几何),也构造了相应的Cartesian认证码,给出了它们的参数。假设编码规则按照一种均匀分布选择,则这些码的成功攻击概率P_I和替换攻击成功概率P_S也被计算。 相似文献
19.
20.
黄梅 《廊坊师范学院学报(自然科学版)》2011,11(6):17-18
Desargues对偶定理主要用于证明仿射平面上的共点线,为使Desargues对偶定理能在初等几何中有所应用,将无穷远点还原为直线的平行,并运用其解决欧氏平面上的线共点问题。 相似文献