基于SVM的足球场地禁区检测

足球比赛中的射门、进球等精彩事件都发生在禁区附近,检测视频中的禁区对足球视频摘要和精彩事件的检测都具有重要意义.提出了一种鲁棒的足球场地禁区检测方法:通过颜色自适应的场地检测方法得到足球比赛场地,然后使用Hough变换检测足球场地中的直线,最后采用SVM 分类器检测图像中是否包含禁区.从实验结果来看,基于SVM的禁区检测算法对球场颜色的变化、直线的误检及漏检有一定的鲁棒性.该算法检测禁区的准确率和查全率均高于96%,可以应用到足球视频内容分析.     

一种基于球场模型的广播足球视频摄像机自动定标方法

随着足球视频语义内容分析和理解、自动视频索引、虚拟增强现实表示等研究的不断深入,摄像机定标技术扮演了越来越重要的角色.基于此,提出了一种基于球场模型的广播足球视频摄像机自动定标算法,该算法建立在所定义的球场模型基础之上,首先通过改进的球场线探测算法得到球场平面的特征点,并求解摄像机同形 (Homography)矩阵,然后,利用所求解的同形矩阵来定位球门,得到球门平面的两个特征点,最后根据基于K均值聚类和Hough-like搜索的方法来得到最优的摄像机内外参数.初步的实验结果表明,依据本文算法所求解的摄像机参数最优值相比初始值精确度更高,并且其在连续帧中也更加稳定.     

足球比赛场景的三维重建和动画生成

介绍一个实用的足球比赛场景三维重建系统。该系统通过比赛的录像片段恢复场景的三维模型 ,包括球员的姿态、位置和足球的运动轨迹 ,允许用户在足球场上漫游 ,从任意的视角观看比赛的进行。通过序列图像 ,系统能够生成一段动画 ,重现精彩的比赛片断。系统通过自动和手工相结合的办法实现特征提取和跟踪过程 ,利用线性定标的方法恢复摄像机视点。经过实验证明 ,该系统重建的模型具有较高的精度 ,误差不超过 1%。     

足球视频三维重建中的摄像机标定及球员检测

在分析现有研究方法的基础上,在LUV颜色空间中利用改进的广义劳埃德聚类算法(GLA)检测并确定球场区域,提出并设计了通过足球视频的禁区和中圈区域实现摄像机标定的方法.利用球场主色,去除了含有球场色的区域并同时虑掉了球场标志线等与球员和球无关的信息,然后使用线填充算法实现球员的连通区域的提取,并最终获取了球员的位置坐标.实验结果验证了算法具有很好的效果.     

带约束的摄像机定标方法

由于积累误差和摄像机内部参数的校正误差,基于视觉的摄像机定标结果尽管在图像上的重投影误差很小,但是重建的空间结构往往存在一定程度的扭曲。提出了一种带约束的摄像机定标算法,将场景中存在几何条件（如摄像机路径在一条直线上）作为约束条件,对摄像机定标结果进行再优化,使得重建的空间与真实世界的欧氏空间更为一致。在优化过程中,将欧氏空间与图像空间的两种误差约束在同一范围,自动获取最佳的约束系数。实验结果证明了该算法的有效性。     

体育视频中场地自动检测方法

主要针对虚拟广告系统设计了简单而有效的算法来实现体育视频中场地检测,首先通过基于颜色空间直方图统计的方法实现了场地主区域的自动提取,再通过Top-Hat变换和改进的最大类间方差法实现了场地边缘检测,最后通过Hough直线检测和最小二乘拟合相结合的方法精确检测到所有的场地线。大量的实验表明,本文提出的场地检测方法对于羽毛球场地,网球场地,乒乓球场地等都有很好的检测效果,提取结果可用于摄像机定标和比赛场地的重建。     

自适应高斯混合模型球场检测算法及其在体育视频分析中的应用

球场检测在体育视频内容分析中有着重要作用．为了克服由于不同光照、不同相机、不同拍摄角度造成球场颜色的非均一性问题，提出了一种基于自适应高斯混合模型（adaptive Gaussian mixture model，GMM）的球场检测算法．该算法首先从视频中任意抽取一些图像，并自动分析这些图像的主要颜色，从中找到主颜色的近似分布，然后，利用GMM拟合主要颜色分布．为提高模型的适应能力，在球场检测过程中，利用当前GMM球场检测结果和增量期望最大（incremental expectation maximum，IEM）算法不断更新模型参数，从而得到更加准确的参数估计，并用于后续图像中球场和非球场像素进行分类．最后，根据球场区域在图像中的分布，对足球比赛场景进行分类．实验证明，提出的算法具有良好的性能．     

基于平行线的室内视觉导航

根据一组空间直线上的无穷远线素集在视平面上所形成的消失点对直线的平移具有稳定性的特点，提出了基于平行线的摄像机参数标定和自主移动平台室内视觉导航算法．在对摄像机进行标定时，将摄像机模型简化成关于移动平台航向角和X方向距离的线性模型，并利用走廊左右踢脚线在视平面上的投影直线的斜率、消失点坐标来标定摄像机的内、外参数；在视觉导航时，视走廊左右踢脚线为一组平行线，由其在视平面上的投影直线的斜率、消失点坐标，控制自主移动平台行驶的X方向距离和航向角，实现平台的室内视觉导航．本文采用YIQ彩色模型分割楼道图像，由Hough变换与最小二乘法相结合的方法提取楼道踢脚线．     

足球比赛精彩场景的自动分析与提取

提出了基于MPEG压缩域音频流的足球比赛精彩场景自动分析与提取算法．首先直接提取出压缩域音频特征；然后基于提取出来的压缩域特征实现解说音的检测和分割，并且分别识别足球比赛中解说员激动解说和观众激昂欢呼两种类型音频事件；最后通过概率融合生成最终结果，融合结果所对应的比赛片段就是提取出的足球比赛精彩场景．实验结果表明了该算法的可行性．     

模型无关的无定标视觉伺服控制

本文首先介绍了视觉伺服的一般原理．然后提出了一种模型无关的无定标视觉伺服控制方法，在这种方法中不需要机器人模型和摄像机模型，应用方差最小化的原理推导出了模型无关的无定标视觉伺服控制律．此外还给出了图像雅可比矩阵的递推公式．文章最后通过一个轨线跟踪的仿真实验验证了算法的正确性和有效性．     

Camera calibration using court models for real-time augmenting soccer scenes

In this paper, we present a procedure to estimate the position, orientation and focal length of a camera in a soccer field. These parameters are then used in real-time overlay of graphics on a soccer pitch. The method uses court model composed by arcs and lines. A means of automatically initializing the tracking process is also presented which uses Hough transform with a combination of a non-linear least squares optimization method. For the tracking of camera parameters, two cases arise: the center of the pitch and the 18 m area. A combination of automatic court model recognition with the Kanade-Lucas-Tomasi (KLT) algorithm is also used.     

Segment Based Camera Calibration

The basic idea of calibrating a camera system in previous approaches is to determine camera parmeters by using a set of known 3D points as calibration reference.In this paper,we present a method of camera calibration in whih camera parameters are determined by a set of 3D lines.A set of constraints is derived on camea parameters in terms of perspective line mapping.Form these constraints,the same perspective transformation matrix as that for point mapping can be computed linearly.The minimum number of calibration lines is 6.This result generalizes that of Liu,Huang and Faugeras^[12] for camera location determination in which at least 8 line correspondences are required for linear computation of camera location.Since line segments in an image can be located easily and more accurately than points,the use of lines as calibration reference tends to ease the computation in inage preprocessing and to improve calibration accuracy.Experimental results on the calibration along with stereo reconstruction are reported.     

Computing camera parameters using vanishing-line information from a rectangular parallelepiped

A new approach to camera calibration using vanishing line information for three-dimensional computer vision is proposed. Calibrated parameters include the orientation, the position, the focal length, and the image plane center of a camera. A rectangular parallelepiped is employed as the calibration target to generate three principal vanishing points and then three vanishing lines from the projected image of the parallelepiped. Only a monocular image is required for solving these camera parameters. It is shown that the image plane center is the orthocenter of a triangle formed by the three vanishing lines. From the slopes of the vanishing lines the camera orientation parameters can be determined. The focal length can be computed by the area of the triangle. The camera position parameters can then be calibrated by using related geometric projective relationships. The derived results show the geometric meanings of these camera parameters. The calibration formulas are analytic and simple to compute. Experimental results show the feasibility of the proposed approach for a practical application—autonomous land vehicle guidance.This work was supported by National Science Council, Republic of China under Grant NSC-77-0404-E-009-31.     

基于平面镜的摄像机内参数线性标定方法

提出了一种全新的基于平面镜的摄像机标定方法。该方法无需任何标定物,利用平面镜的反射性质和灭点、灭线等理论,通过移动摄像机或平面镜作至少2次平移运动(各次平移间应存在旋转运动)即可线性地标定摄像机的内参数。模拟图像实验和真实图像实验表明所提出的方法能快速、方便地对摄像机进行标定,具有较好的稳定性和精度。     

Robust Image Mosaicing of Soccer Videos using Self-Calibration and Line Tracking

In this paper we propose an accurate and robust image mosaicing method of soccer video taken from a rotating and zooming camera using line tracking and self-calibration. The mosaicing of soccer videos is not easy, because their playing fields are low textured and moving players are included in the fields. Our approach is to track line features on the playing fields. The line features are detected and tracked using a self-calibration technique for a rotating and zooming camera. To track line features efficiently, we propose a new line tracking algorithm, called camera parameter guided line tracking, which works even when the camera motion undergoes sudden changes. Since we do not need to know any model for scenes beforehand, the proposed algorithm can be easily extended to other video sources, as well as other sports videos. Experimental results show the accuracy and robustness of the algorithm. An application of mosaicing is also presented.     

Non-goal scene analysis for soccer video

The broadcast soccer video is usually recorded by one main camera, which is constantly gazing somewhere of playfield where a highlight event is happening. So the camera parameters and their variety have close relationship with semantic information of soccer video, and much interest has been caught in camera calibration for soccer video. The previous calibration methods either deal with goal scene, or have strict calibration conditions and high complexity. So, it does not properly handle the non-goal scene such as midfield or center-forward scene. In this paper, based on a new soccer field model, a field symbol extraction algorithm is proposed to extract the calibration information. Then a two-stage calibration approach is developed which can calibrate camera not only for goal scene but also for non-goal scene. The preliminary experimental results demonstrate its robustness and accuracy.     

基于Harris角点的内窥镜图像变形全自动校正算法

提出一种基于Harris角点检测的全自动内窥镜图像变形校正算法. 对一幅黑白棋格图像进行Harris特征点检测并将特征按所属直线进行自动归类. 引入关于全体变形参数的Harris角点子集直线度函数并对它进行Levenberg-Marquardt迭代优化来寻找最优变形参数. 获取图像时无需限定相机与标定图案的相对姿态,算法执行中无需用户交互式干预. 实验结果表明本文算法的校正结果使得内窥镜成像很好地满足线性相机模型,具有亚像素级精 度,是一种快速简单灵活的校正方法,尤其适合临床应用.     

半结构化环境稀疏点云可通行区域检测方法

传统的激光雷达可通行区域检测算法实时性好,但算法通常对点云数据的高度特征依赖较强,半结构化环境中斜坡等区域高度特征不稳定,易降低算法的性能。基于半结构化环境下三维稀疏点云数据,提出了一种基于直线特征的可通行区域实时检测算法,预处理原始点云数据,并从中速提取直线特征;对直线聚类和筛选,从而提取有效的直线特征;使用直线特征检测结构化障碍物和非结构化障碍物;标记出可通行区域,并构建环境地图。实验结果表明,在校园半结构化环境中,该算法可以较稳定地检测可通行区域,在检测路缘石等高度较低的障碍物时表现出良好的性能,并且适应斜坡、颠簸、负障碍等地面。     

一种稳健的直线提取和匹配算法

在空间机器人遥操作中,需要快速的求解图像的摄像机参数来对操作对象进行三维建模.通过利用匹配直线的对应关系,可以直接求出图像的摄像机参数,而且比用角点匹配求得的结果具有更高的可靠性.现有的直线提取和匹配算法虽然已经有很多,但是大部分都比较耗时,不能满足实时性的要求.针对空间机器人遥操作等实时性较强的应用,提出了一种基于直线支持区域的稳健、快速的直线提取和匹配算法.实验结果表明了该算法的有效性.