%0 Journal Article %J Signal Processing, IEEE Transactions on %D 2005 %T Data hiding in curves with application to fingerprinting maps %A Gou,Hongmei %A M. Wu %K (mathematics); %K algorithm; %K alignment-minimization %K B-spline %K CONTROL %K curve %K data %K detection; %K edge %K embedding; %K encapsulation; %K fingerprint %K geospatial %K hiding %K identification; %K image %K iterative %K method; %K methods; %K minimisation; %K point; %K protection; %K registration; %K sequence; %K spectrum %K splines %K spread %K watermarking; %X This paper presents a new data hiding method for curves. The proposed algorithm parameterizes a curve using the B-spline model and adds a spread spectrum sequence to the coordinates of the B-spline control points. In order to achieve robust fingerprint detection, an iterative alignment-minimization algorithm is proposed to perform curve registration and to deal with the nonuniqueness of B-spline control points. Through experiments, we demonstrate the robustness of the proposed data-hiding algorithm against various attacks, such as collusion, cropping, geometric transformations, vector/raster-raster/vector conversions, printing-and-scanning, and some of their combinations. We also show the feasibility of our method for fingerprinting topographic maps as well as writings and drawings. %B Signal Processing, IEEE Transactions on %V 53 %P 3988 - 4005 %8 2005/10// %@ 1053-587X %G eng %N 10 %R 10.1109/TSP.2005.855411 %0 Conference Paper %B Shape Modeling and Applications, 2005 International Conference %D 2005 %T The half-edge tree: a compact data structure for level-of-detail tetrahedral meshes %A Danovaro,E. %A De Floriani, Leila %A Magillo,P. %A Puppo,E. %A Sobrero,D. %A Sokolovsky,N. %K application; %K compact %K computational %K data %K detection; %K edge %K encoding; %K generation; %K geometry; %K half-edge %K iterative %K level-of-detail %K mesh %K meshes; %K methods; %K model; %K structure; %K structures; %K tetrahedral %K tree %K tree; %X We propose a new data structure for the compact encoding of a level-of detail (LOD) model of a three-dimensional scalar field based on unstructured tetrahedral meshes. Such data structure, called a half-edge tree (HET), is built through the iterative application of a half-edge collapse, i.e. by contracting an edge to one of its endpoints. We also show that selective refined meshes extracted from an HET contain on average about 34% and up to 75% less tetrahedra than those extracted from an LOD model built through a general edge collapse. %B Shape Modeling and Applications, 2005 International Conference %P 332 - 337 %8 2005/06// %G eng %R 10.1109/SMI.2005.47 %0 Conference Paper %B Image Processing, 2005. ICIP 2005. IEEE International Conference on %D 2005 %T Segmentation and appearance model building from an image sequence %A Liang Zhao %A Davis, Larry S. %K algorithm; %K color-path-length %K expectation-sampling %K image %K iterative %K joint %K kernel-based %K methods; %K PDF; %K person %K segmentation; %K sequence; %K sequences; %K space; %X In this paper we explore the problem of accurately segmenting a person from a video given only approximate location of that person. Unlike previous work which assumes that the appearance model is known in advance, we developed an iterative expectation-sampling (ES) algorithm for solving segmentation and appearance modeling simultaneously The appearance model is encoded with a kernel-based PDF defined in a joint color/path-length space. This appearance model remains unchanged during a short time period, although the object can articulate. Thus, we can perform the ES iteration not only for a single frame but also for an image sequence. The algorithm is iterative, but simple, efficient and gives visually good results. %B Image Processing, 2005. ICIP 2005. IEEE International Conference on %V 1 %P I - 321-4 - I - 321-4 %8 2005/09// %G eng %R 10.1109/ICIP.2005.1529752 %0 Conference Paper %B Pattern Recognition, 2004. ICPR 2004. Proceedings of the 17th International Conference on %D 2004 %T Iterative figure-ground discrimination %A Zhao, L. %A Davis, Larry S. %K algorithm; %K analysis; %K Bandwidth %K calculation; %K Color %K colour %K Computer %K density %K dimensional %K discrimination; %K distribution; %K distributions; %K Estimation %K estimation; %K expectation %K figure %K Gaussian %K ground %K image %K initialization; %K iterative %K Kernel %K low %K methods; %K mixture; %K model %K model; %K nonparametric %K parameter %K parametric %K processes; %K sampling %K sampling; %K segmentation %K segmentation; %K statistics; %K theory; %K vision; %X Figure-ground discrimination is an important problem in computer vision. Previous work usually assumes that the color distribution of the figure can be described by a low dimensional parametric model such as a mixture of Gaussians. However, such approach has difficulty selecting the number of mixture components and is sensitive to the initialization of the model parameters. In this paper, we employ non-parametric kernel estimation for color distributions of both the figure and background. We derive an iterative sampling-expectation (SE) algorithm for estimating the color, distribution and segmentation. There are several advantages of kernel-density estimation. First, it enables automatic selection of weights of different cues based on the bandwidth calculation from the image itself. Second, it does not require model parameter initialization and estimation. The experimental results on images of cluttered scenes demonstrate the effectiveness of the proposed algorithm. %B Pattern Recognition, 2004. ICPR 2004. Proceedings of the 17th International Conference on %V 1 %P 67 - 70 Vol.1 - 67 - 70 Vol.1 %8 2004/08// %G eng %R 10.1109/ICPR.2004.1334006 %0 Conference Paper %B Image Processing, 2004. ICIP '04. 2004 International Conference on %D 2004 %T Multiple view tracking of humans modelled by kinematic chains %A Sundaresan, A. %A Chellapa, Rama %A RoyChowdhury, R. %K 3D %K algorithm; %K analysis; %K body %K calibrated %K cameras; %K chain %K displacement; %K error %K estimation; %K human %K image %K iterative %K kinematic %K kinematics; %K methods; %K model; %K MOTION %K motion; %K multiple %K parameters; %K perspective %K Pixel %K processing; %K projection %K sequences; %K signal %K tracking; %K video %K view %X We use a kinematic chain to model human body motion. We estimate the kinematic chain motion parameters using pixel displacements calculated from video sequences obtained from multiple calibrated cameras to perform tracking. We derive a linear relation between the 2D motion of pixels in terms of the 3D motion parameters of various body parts using a perspective projection model for the cameras, a rigid body motion model for the base body and the kinematic chain model for the body parts. An error analysis of the estimator is provided, leading to an iterative algorithm for calculating the motion parameters from the pixel displacements. We provide experimental results to demonstrate the accuracy of our formulation. We also compare our iterative algorithm to the noniterative algorithm and discuss its robustness in the presence of noise. %B Image Processing, 2004. ICIP '04. 2004 International Conference on %V 2 %P 1009 - 1012 Vol.2 - 1009 - 1012 Vol.2 %8 2004/10// %G eng %R 10.1109/ICIP.2004.1419472 %0 Conference Paper %B Image Processing, 2004. ICIP '04. 2004 International Conference on %D 2004 %T Robust ego-motion estimation and 3D model refinement using depth based parallax model %A Agrawala, Ashok K. %A Chellapa, Rama %K 3D %K algorithm; %K analysis; %K and %K based %K camera; %K coarse %K compensation; %K DEM; %K depth %K digital %K ego-motion %K eigen-value %K eigenfunctions; %K eigenvalues %K ELEVATION %K epipolar %K estimation; %K extraction; %K feature %K field; %K iteration %K iterative %K map; %K method; %K methods; %K model %K model; %K MOTION %K parallax %K partial %K range-finding; %K refinement; %K refining; %K surface %X We present an iterative algorithm for robustly estimating the ego-motion and refining and updating a coarse, noisy and partial depth map using a depth based parallax model and brightness derivatives extracted from an image pair. Given a coarse, noisy and partial depth map acquired by a range-finder or obtained from a Digital Elevation Map (DFM), we first estimate the ego-motion by combining a global ego-motion constraint and a local brightness constancy constraint. Using the estimated camera motion and the available depth map estimate, motion of the 3D points is compensated. We utilize the fact that the resulting surface parallax field is an epipolar field and knowing its direction from the previous motion estimates, estimate its magnitude and use it to refine the depth map estimate. Instead of assuming a smooth parallax field or locally smooth depth models, we locally model the parallax magnitude using the depth map, formulate the problem as a generalized eigen-value analysis and obtain better results. In addition, confidence measures for depth estimates are provided which can be used to remove regions with potentially incorrect (and outliers in) depth estimates for robustly estimating ego-motion in the next iteration. Results on both synthetic and real examples are presented. %B Image Processing, 2004. ICIP '04. 2004 International Conference on %V 4 %P 2483 - 2486 Vol. 4 - 2483 - 2486 Vol. 4 %8 2004/10// %G eng %R 10.1109/ICIP.2004.1421606 %0 Conference Paper %B INFOCOM 2003. Twenty-Second Annual Joint Conference of the IEEE Computer and Communications. IEEE Societies %D 2003 %T Construction of an efficient overlay multicast infrastructure for real-time applications %A Banerjee,S. %A Kommareddy,C. %A Kar,K. %A Bhattacharjee, Bobby %A Khuller, Samir %K application-layer; %K applications; %K communication; %K criterion; %K decentralized %K distributed %K entities; %K forwarding %K infrastructure; %K Internet; %K iterative %K media-streaming %K methods; %K MSN; %K Multicast %K nodes; %K NP-hard; %K OPTIMIZATION %K overlay %K real %K real-time %K scheme; %K service %K systems; %K TIME %X This paper presents an overlay architecture where service providers deploy a set of service nodes (called MSNs) in the network to efficiently implement media-streaming applications. These MSNs are organized into an overlay and act as application-layer multicast forwarding entities for a set of clients. We present a decentralized scheme that organizes the MSNs into an appropriate overlay structure that is particularly beneficial for real-time applications. We formulate our optimization criterion as a "degree-constrained minimum average-latency problem" which is known to be NP-hard. A key feature of this formulation is that it gives a dynamic priority to different MSNs based on the size of its service set. Our proposed approach iteratively modifies the overlay tree using localized transformations to adapt with changing distribution of MSNs, clients, as well as network conditions. We show that a centralized greedy approach to this problem does not perform quite as well, while our distributed iterative scheme efficiently converges to near-optimal solutions. %B INFOCOM 2003. Twenty-Second Annual Joint Conference of the IEEE Computer and Communications. IEEE Societies %V 2 %P 1521 - 1531 vol.2 - 1521 - 1531 vol.2 %8 2003/04/03/march %G eng %R 10.1109/INFCOM.2003.1208987 %0 Conference Paper %B Image Processing, 2003. ICIP 2003. Proceedings. 2003 International Conference on %D 2003 %T Mean-shift analysis using quasiNewton methods %A Yang,C. %A Duraiswami, Ramani %A DeMenthon,D. %A Davis, Larry S. %K analysis; %K classification; %K clustering %K clustering; %K Convergence %K density %K estimation; %K feature-space %K image %K irregular %K iterative %K Mean-shift %K method; %K methods; %K Newton %K nonparametric %K pattern %K procedure; %K quasiNewton %K rates; %K segmentation; %K technique; %K topography; %X Mean-shift analysis is a general nonparametric clustering technique based on density estimation for the analysis of complex feature spaces. The algorithm consists of a simple iterative procedure that shifts each of the feature points to the nearest stationary point along the gradient directions of the estimated density function. It has been successfully applied to many applications such as segmentation and tracking. However, despite its promising performance, there are applications for which the algorithm converges too slowly to be practical. We propose and implement an improved version of the mean-shift algorithm using quasiNewton methods to achieve higher convergence rates. Another benefit of our algorithm is its ability to achieve clustering even for very complex and irregular feature-space topography. Experimental results demonstrate the efficiency and effectiveness of our algorithm. %B Image Processing, 2003. ICIP 2003. Proceedings. 2003 International Conference on %V 2 %P II - 447-50 vol.3 - II - 447-50 vol.3 %8 2003/09// %G eng %R 10.1109/ICIP.2003.1246713 %0 Conference Paper %B Motion and Video Computing, 2002. Proceedings. Workshop on %D 2002 %T A hierarchical approach for obtaining structure from two-frame optical flow %A Liu,Haiying %A Chellapa, Rama %A Rosenfeld, A. %K algorithm; %K aliasing; %K analysis; %K computer-rendered %K depth %K depth; %K error %K estimation; %K extraction; %K Face %K feature %K flow; %K gesture %K hierarchical %K image %K images; %K inverse %K iterative %K methods; %K MOTION %K nonlinear %K optical %K parameter %K processing; %K real %K recognition; %K sequences; %K signal %K structure-from-motion; %K system; %K systems; %K TIME %K two-frame %K variation; %K video %X A hierarchical iterative algorithm is proposed for extracting structure from two-frame optical flow. The algorithm exploits two facts: one is that in many applications, such as face and gesture recognition, the depth variation of the visible surface of an object in a scene is small compared to the distance between the optical center and the object; the other is that the time aliasing problem is alleviated at the coarse level for any two-frame optical flow estimate so that the estimate tends to be more accurate. A hierarchical representation for the relationship between the optical flow, depth, and the motion parameters is derived, and the resulting non-linear system is iteratively solved through two linear subsystems. At the coarsest level, the surface of the object tends to be flat, so that the inverse depth tends to be a constant, which is used as the initial depth map. Inverse depth and motion parameters are estimated by the two linear subsystems at each level and the results are propagated to finer levels. Error analysis and experiments using both computer-rendered images and real images demonstrate the correctness and effectiveness of our algorithm. %B Motion and Video Computing, 2002. Proceedings. Workshop on %P 214 - 219 %8 2002/12// %G eng %R 10.1109/MOTION.2002.1182239