自适应的数码相机自动白平衡算法

提出了一种色温估计方法,并在此基础上实现了一个自适应的数码相机自动白平衡算法．该算法充分考虑了Y和Cb,Cr之间的相关性,挑选更合适的白色像素进行平均色差计算,以提高色温估计的精度．在一个数码相机处理器的设计中实现了该算法．测试结果表明该算法的色温估计精度比传统算法有较大提高．     

面向运动过程建模的运动模糊图像摄像机响应函数估计方法

摄像机响应函数是将图像辐照度映射到图像强度的非线性函数,目前的运动模糊去除算法并没有考虑成像过程中摄像机响应函数的影响,不可避免地存在去模糊效果不佳的现象.通过研究运动模糊图像的摄像机响应函数估计问题,提出能量累积形成模糊的运动过程和摄像机响应函数相结合的摄像机响应函数求解模型,并进一步基于该运动过程模型提出一幅或多幅运动模糊图像的摄像机响应函数求解方法.首先选择一些与局部运动方向不平行的模糊边界,然后根据这些边界的模糊形成过程简化摄像机响应函数求解模型,实现摄像机响应函数求解.该方法没有苛刻的平行边界要求,较已有方法更加灵活.摄像机响应函数的求解实验及运动模糊图像去模糊实验结果表明,文中的求解摄像机响应函数模型和方法是准确的,利用该响应函数可提高对运动模糊的去除效果.     

采用同心圆图像的摄像机标定方法

为研究计算机视觉问题,介绍了一种新的采用同心圆图像进行摄像机内参数标定的算法,在标定中,采用了针孔摄像机模型.与已有的方法不同,算法以3D圆的投影方程为基础,包含了摄像机的内部参数矩阵.根据其在代数上的特殊形式,可以得到关于摄像机内部参数的一个线性方程组,通过创建足够的方程组,可以很容易求得所有的摄像机内部参数.方法是完全线性的算法,无需迭代优化,无需求取虚圆点,仅需要三幅两同心圆的图像即可实现全部摄像机内部参数的标定.最后通过仿真验证了内参数标定算法的准确性和鲁棒性.     

BSSRDF Estimation from Single Images

We present a novel method to estimate an approximation of the reflectance characteristics of optically thick, homogeneous translucent materials using only a single photograph as input. First, we approximate the diffusion profile as a linear combination of piecewise constant functions, an approach that enables a linear system minimization and maximizes robustness in the presence of suboptimal input data inferred from the image. We then fit to a smoother monotonically decreasing model, ensuring continuity on its first derivative. We show the feasibility of our approach and validate it in controlled environments, comparing well against physical measurements from previous works. Next, we explore the performance of our method in uncontrolled scenarios, where neither lighting nor geometry are known. We show that these can be roughly approximated from the corresponding image by making two simple assumptions: that the object is lit by a distant light source and that it is globally convex, allowing us to capture the visual appearance of the photographed material. Compared with previous works, our technique offers an attractive balance between visual accuracy and ease of use, allowing its use in a wide range of scenarios including off‐the‐shelf, single images, thus extending the current repertoire of real‐world data acquisition techniques.     

高光谱影像光谱响应曲线分维计算

高光谱影像光谱响应曲线包含丰富的光谱特征,分形维值可以表征复杂光谱响应曲线特征,提出了步长测量法光谱响应曲线分形维值计算算法及高光谱分形特征影像的生成流程,对OMIS影像上不同类型地物样本的光谱曲线分维特征计算结果表明,分维是一种有效表达像元光谱信息的特征值。讨论了光谱响应曲线分维值对于高光谱数据处理的意义。     

基于手持单相机序列图像的三维重建

提出了基于手持单相机序列图像的射影和欧氏重建方法。利用编码点确定单相机的外部姿态参数,非编码点确定空间点的三维坐标。施加绝对二次曲面的本质条件到射影畸变矩阵中,提高了算法的鲁棒性。实验结果表明,该方法的3D重建结果精确可靠,能够满足逆向工程等应用的要求。     

Variational Reflectance Estimation from Multi-view Images

We tackle the problem of reflectance estimation from a set of multi-view images, assuming known geometry. The approach we put forward turns the input images into reflectance maps, through a robust variational method. The variational model comprises an image-driven fidelity term and a term which enforces consistency of the reflectance estimates with respect to each view. If illumination is fixed across the views, then reflectance estimation remains under-constrained: A regularization term, which ensures piecewise-smoothness of the reflectance, is thus used. Reflectance is parameterized in the image domain, rather than on the surface, which makes the numerical solution much easier, by resorting to an alternating majorization–minimization approach. Experiments on both synthetic and real-world datasets are carried out to validate the proposed strategy.     

Dual Computation of Projective Shape and Camera Positions from Multiple Images

International Journal of Computer Vision - Given multiple image data from a set of points in 3D, there are two fundamental questions that can be addressed: What is the structure of the set of...     

基于摄像机纵向运动的序列图像的实时漫游

对于摄像机纵向运动的序列图像,提出了一种基于极线几何约束关系的当前视点目标图像生成算法：1）利用基于傅立叶变换的方法,得到远视点源图像中和近视点源图像无对应点的区域,并用一种背景色将其填充,得到填充后的远视点源图像;2）利用极线的整体匹配性质在两幅源图像中确定遍历整个源图像的对应源极线;3）将所有对应源极线按灰度进行分段;4）用动态规划匹配法确定对应源极线上段与段之间的匹配关系;5）通过两条对应源极线插值合成一条目标极线,生成当前视点的目标图像;6）对上一步得到的目标图像的背景色区域加以处理,得到最终的当前视点目标图像．提出了一种链表数据结构存储每相邻两幅源图像之间的预处理信息．漫游时实时读取．开发了一个图像漫游器,使用户能在其中实现不同视点的实时漫游．     

一种深度图像中的表面曲率估计算法

曲率估计在深度图像分析中占有重要地位,传统的有限差分或局部拟合方法未考虑到表面上可能出现的不连续性,因而会不可避免地出现错误,为了得到有效可靠的曲率估计,本文提出了基于自适应局部表面拟合和鲁棒最大似然的估计的曲率估计算法,首先,提出曲面是分片光滑的假设,表面曲率需从该像素所属的光滑曲面片来估计,其次,定义了能量函数来度量拟合窗的平滑度,在局部表面拟合时,依据最小化能量函数的原则来自适应移动拟合窗的中心,以使拟合窗达到最“光滑”,最后,采用鲁棒最大似然估计以消除仍然存在的“局外点”的影响,理论分析和实验结果证明估计算法是稳健,可靠,有效的且计算复杂度小。     

Estimation of Intrinsic Volumes from Digital Grey-Scale Images

Local algorithms are common tools for estimating intrinsic volumes from black-and-white digital images. However, these algorithms are typically biased in the design based setting, even when the resolution tends to infinity. Moreover, images recorded in practice are most often blurred grey-scale images rather than black-and-white. In this paper, an extended definition of local algorithms, applying directly to grey-scale images without thresholding, is suggested. We investigate the asymptotics of these new algorithms when the resolution tends to infinity and apply this to construct estimators for surface area and integrated mean curvature that are asymptotically unbiased in certain natural settings.     

Point Light Source Estimation from Two Images and Its Limits

In this paper, the performance of parameter estimation of a single static distant point light source from two video images is analyzed in terms of estimation theory. The illumination parameters are the intensity and direction of the light source.In the first part of this paper, estimators from the literature are reviewed. Most recent estimators evaluate as input data two video images as well as the 3D shape and the 3D motion of the visible moving objects.In the second part of the paper, the performance of these recent methods is analyzed. The input data to estimation as well as the inherent input data errors are described by a stochastic observation model. Based on this model, the performance is analyzed regarding the Cramér-Rao theoretical lower bound of estimation error variances. The bound is derived for a variety of cases of scene illumination, object motion and errors in input data. For simplification purpose, the bound is valid only for object motions with the rotation axis lying in the image plane. The analysis shows in which cases which estimation accuracy can be expected with current methods.Finally, a comparison of the bound with one of the recent estimators shows that recent estimators are suboptimal in case of errors in the 3D shape of the objects. In future work, the stochastic observation model presented in this paper can be used to improve illumination estimation.     

Q-PSO: Fast Quaternion-Based Pose Estimation from RGB-D Images

This paper investigates the leader–follower formation control problem for a group of networked nonholonomic mobile robots that are subject to bounded time-varying communication delays and an asynchronous clock. First we convert the formation control problem into a trajectory tracking problem, and then a fully distributed unified control framework based on the receding horizon control is implemented to converge the tracking errors. By adding an auxiliary acceleration term into the receding horizon controller, the framework is able to solve the impractical velocity jump problem. Considering the time-varying delays, the timing and order features of the messages are utilized to guarantee their logical correctness. To compensate for the delay effect, an improved control framework that exploits the predictability of the receding horizon controller is proposed. The asynchronous clock problem, which makes the communication delay unmeasurable, is studied. We give a definition of the syn point that is inspired from investigation of the property that messages are received out of order in a bounded time-varying delayed network. A novel method that detects the occurrence of syn points is integrated into the control framework to solve the asynchronous clock problem. Finally the effectiveness of the proposed approaches is demonstrated in the Player/Stage simulation environment.     

基于马尔可夫随机场的单目图像深度估计

图像深度获取是机器视觉领域活跃的研究课题。将图像深度估计问题归结为模式识别问题,以单目图像深度为待分连续模式类,在多尺度下对图像块提取绝对和相对深度特征,选择表征上下文关系的MRF（Markov Random Field）-MAP（Maximum a posteriori）方法,建立拉普拉斯模型,表述某图像块的深度和其邻域深度之间的关系。实验得到了某一类单目图像对应的深度图像,证明了该算法的有效性。     

Detecting and Handling Unreliable Points for Camera Parameter Estimation

The popularly used DLT method sometimes fails to give reliable camera parameter estimation. It is therefore important to detect the unreliability and provide the corresponding solutions. Based on a complete framework of invariance for six points, we construct two evaluation functions to detect the unreliability. The two evaluation functions do not involve any computations for the camera projective matrix or optical center and thus are efficient to perform the detection. Then, the guidelines corresponding to the different detection results are presented. In particular, a filtering RANSAC method to remove the detected unreliable points is provided. The filtering RANSAC proves to be successful in removing the unreliable points even if these points are of a large proportion.     

Learned Models for Estimation of Rigid and Articulated Human Motion from Stationary or Moving Camera

We propose an approach for modeling, measurement and tracking of rigid and articulated motion as viewed from a stationary or moving camera. We first propose an approach for learning temporal-flow models from exemplar image sequences. The temporal-flow models are represented as a set of orthogonal temporal-flow bases that are learned using principal component analysis of instantaneous flow measurements. Spatial constraints on the temporal-flow are then incorporated to model the movement of regions of rigid or articulated objects. These spatio-temporal flow models are subsequently used as the basis for simultaneous measurement and tracking of brightness motion in image sequences. Then we address the problem of estimating composite independent object and camera image motions. We employ the spatio-temporal flow models learned through observing typical movements of the object from a stationary camera to decompose image motion into independent object and camera motions. The performance of the algorithms is demonstrated on several long image sequences of rigid and articulated bodies in motion.     

基于人工免疫识别系统的年龄估计

人的年龄变化是引起人脸外观变化的主要原因,由于每个人的生活方式和条件不同,所以很难准确的从人脸图像中估计人的年龄。为此,论文提出一种基于人脸图像的年龄估计方法,利用AAM方法自动提取用于年龄估计的人脸特征,然后按不同年龄段将特征进行分类,为了提高分类的准确性,提出了一种基于PARTIALHAUSDORFF距离的人工免疫识别系统方法,给出了系统的训练、分类实现过程,实验证明了该方法的正确性。     

Data Processing Algorithms for Generating Textured 3D Building Facade Meshes from Laser Scans and Camera Images

In this paper, we develop a set of data processing algorithms for generating textured facade meshes of cities from a series of vertical 2D surface scans and camera images, obtained by a laser scanner and digital camera while driving on public roads under normal traffic conditions. These processing steps are needed to cope with imperfections and non-idealities inherent in laser scanning systems such as occlusions and reflections from glass surfaces. The data is divided into easy-to-handle quasi-linear segments corresponding to approximately straight driving direction and sequential topological order of vertical laser scans; each segment is then transformed into a depth image. Dominant building structures are detected in the depth images, and points are classified into foreground and background layers. Large holes in the background layer, caused by occlusion from foreground layer objects, are filled in by planar or horizontal interpolation. The depth image is further processed by removing isolated points and filling remaining small holes. The foreground objects also leave holes in the texture of building facades, which are filled by horizontal and vertical interpolation in low frequency regions, or by a copy-paste method otherwise. We apply the above steps to a large set of data of downtown Berkeley with several million 3D points, in order to obtain texture-mapped 3D models.     

海量图片的分布式存储及负载均衡研究

针对海量图片给网站带来的访问速度下降、性能压力增大和I/O瓶颈等问题,提出一种海量图片的分布式存储及负载均衡技术。通过把图片数据和网站内容分开部署、在数据库中记录和维护图片服务器状态信息等方法实现图片和页面数据的分离。实验结果表明,该技术能提高网站的访问速度和运行效率,并可动态增加图片服务器的数量满足日益增加的性能需求。