OpenRaiser/Intern-Atlas huggingface dataset:
Tracking distributions with an overlap prior
Authors: Ismail Ben Ayed, Shuo Li 0001, Ian G. Ross
Venue: CVPR
Year: 2008

Recent studies have shown that embedding similarity/dissimilarity measures between distributions in the variational level set framework can lead to effective object segmentation/tracking algorithms. In this connection, existing methods assume implicitly that the overlap between the distributions of image data within the object and its background has to be minimal. Unfortunately, such assumption may not be valid in many important applications. This study investigates an overlap prior, which embeds knowledge about the overlap between the distributions of the object and the background in level set tracking. It consists of evolving a curve to delineate the target object in the current frame. The level set curve evolution equation is sought following the maximization of a functional containing three terms: (1) an original overlap prior which measures the conformity of overlap between the nonparametric (kernel-based) distributions within the object and the background to a learned description, (2) a term which measures the similarity between a model distribution of the object and the sample distribution inside the curve, and (3) a regularization term for smooth segmentation boundaries. The Bhattacharyya coefficient is used as an overlap measure. Apart from leading to a method which is more versatile than current ones, the overlap prior speeds up significantly the curve evolution. Comparisons and results demonstrate the advantages of the proposed prior over related methods, and its usefulness in important applications such as the left ventricle tracking in magnetic resonance (MR) images.
Utilizing semantic word similarity measures for video retrieval
Authors: Yusuf Aytar, Mubarak Shah, Jiebo Luo 0001
Venue: CVPR
Year: 2008

This is a high level computer vision paper, which employs concepts from Natural Language Understanding in solving the video retrieval problem. Our main contribution is the utilization of the semantic word similarity measures (Lin and PMI-IR similarities) for video retrieval. In our approach, we use trained concept detectors, and the visual co-occurrence relations between such concepts. We propose two methods for content-based retrieval of videos: (1) A method for retrieving a <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">new</b> <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">concept</b> (a concept which is not known to the system, and no annotation is available) using semantic word similarity and visual co-occurrence. (2) A method for retrieval of videos based on their relevance to a user defined text query using the semantic word similarity and visual content of videos. For evaluation purposes, we have mainly used the automatic search and the high level feature extraction test set of TRECVIDpsila06 benchmark, and the automatic search test set of TRECVIDpsila07. These two data sets consist of 250 hours of multilingual news video captured from American, Arabic, German and Chinese TV channels. Although our method for retrieving a new concept is an unsupervised method, it outperforms the trained concept detectors (which are supervised) on 7 out of 20 test concepts, and overall it performs very close to the trained detectors. On the other hand, our visual content based semantic retrieval method performs 81% better than the text-based retrieval method. This shows that using visual content alone we can obtain significantly good retrieval results.
Beyond the Lambertian assumption: A generative model for Apparent BRDF fields of faces using anti-symmetric tensor splines
Authors: Angelos Barmpoutis, Ritwik Kumar, Baba C. Vemuri, Arunava Banerjee
Venue: CVPR
Year: 2008

Human faces are neither exactly Lambertian nor entirely convex and hence most models in literature which make the Lambertian assumption, fall short when dealing with specularities and cast shadows. In this paper, we present a novel anti-symmetric tensor spline (a spline for tensor-valued functions) based method for the estimation of the Apparent BRDF (ABRDF) field for human faces that seamlessly accounts for specularities and cast shadows. Furthermore, unlike other methods, it does not require any 3D information to build the model and can work with as few as 9 images. In order to validate the accuracy of our anti-symmetric tensor spline model, we present a novel approximation of the ABRDF using a continuous mixture of single-lobed spherical functions. We demonstrate the effectiveness of our anti-symmetric tensor-spline model in comparison to other popular models in the literature, by presenting extensive results for face relighting and face recognition using the Extended Yale B database.
Graph commute times for image representation
Authors: Régis Behmo, Nikos Paragios, Véronique Prinet
Venue: CVPR
Year: 2008

We introduce a new image representation that encompasses both the general layout of groups of quantized local invariant descriptors as well as their relative frequency. A graph of interest points clusters is constructed and we use the matrix of commute times between the different nodes of the graph to obtain a description of their relative arrangement that is robust to large intra class variation. The obtained high dimensional representation is then embedded in a space of lower dimension by exploiting the spectral properties of the graph made of the different images. Classification tasks can be performed in this embedding space. We expose classification and labelling results obtained on three different datasets, including the challenging PASCAL VOC2007 dataset. The performances of our approach compare favorably with the standard bag of features, which is a particular case of our representation.
An LED-only BRDF measurement device
Authors: Moshe Ben-Ezra, Jiaping Wang, Bennett Wilburn, Xiaoyang Li, Le Ma
Venue: CVPR
Year: 2008

Light emitting diodes (LEDs) can be used as light detectors and as light emitters. In this paper, we present a novel BRDF measurement device consisting exclusively of LEDs. Our design can acquire BRDFs over a full hemisphere, or even a full sphere (for the bidirectional transmittance distribution function BTDF), and can also measure a (partial) multi-spectral BRDF. Because we use no cameras, projectors, or even mirrors, our design does not suffer from occlusion problems. It is fast, significantly simpler, and more compact than existing BRDF measurement designs.
Accurate multi-view reconstruction using robust binocular stereo and surface meshing
Authors: Derek Bradley, Tamy Boubekeur, Wolfgang Heidrich
Venue: CVPR
Year: 2008

This paper presents a new algorithm for multi-view reconstruction that demonstrates both accuracy and efficiency. Our method is based on robust binocular stereo matching, followed by adaptive point-based filtering of the merged point clouds, and efficient, high-quality mesh generation. All aspects of our method are designed to be highly scalable with the number of views. Our technique produces the most accurate results among current algorithms for a sparse number of viewpoints according to the Middlebury datasets. Additionally, we prove to be the most efficient method among non-GPU algorithms for the same datasets. Finally, our scaled-window matching technique also excels at reconstructing deformable objects with high-curvature surfaces, which we demonstrate with a number of examples.
A factorization approach to structure from motion with shape priors
Authors: Alessio Del Bue
Venue: CVPR
Year: 2008

This paper presents an approach for including 3D prior models into a factorization framework for structure from motion. The proposed method computes a closed-form affine fit which mixes the information from the data and the 3D prior on the shape structure. Moreover, it is general in regards to different classes of objects treated: rigid, articulated and deformable. The inclusion of the shape prior may aid the inference of camera motion and 3D structure components whenever the data is degenerate (i.e. nearly planar motion of the projected shape). A final non-linear optimization stage, which includes the shape priors as a quadratic cost, upgrades the affine fit to metric. Results on real and synthetic image sequences, which present predominant degenerate motion, make clear the improvements over the 3D reconstruction.
Fast and robust numerical solutions to minimal problems for cameras with radial distortion
Authors: Martin Byröd, Zuzana Kukelova, Klas Josephson, Tomás Pajdla, Kalle Åström
Venue: CVPR
Year: 2008

A number of minimal problems of structure from motion for cameras with radial distortion have recently been studied and solved in some cases. These problems are known to be numerically very challenging and in several cases there exist no known practical algorithm yielding solutions in floating point arithmetic. We make some crucial observations concerning the floating point implementation of Gröbner basis computations and use these new insights to formulate fast and stable algorithms for two minimal problems with radial distortion previously solved in exact rational arithmetic only: (i) simultaneous estimation of essential matrix and a common radial distortion parameter for two partially calibrated views and six image point correspondences and (ii) estimation of fundamental matrix and two different radial distortion parameters for two uncalibrated views and nine image point correspondences. We demonstrate on simulated and real experiments that these two problems can be efficiently solved in floating point arithmetic.
Annotating collections of photos using hierarchical event and scene models
Authors: Liangliang Cao, Jiebo Luo 0001, Henry A. Kautz, Thomas S. Huang
Venue: CVPR
Year: 2008

Most image annotation systems consider a single photo at a time and label photos individually. In this work, we focus on collections of personal photos and explore the associated GPS and time information for semantic annotation. First, we employ a constrained clustering method to partition a photo collection into event-based sub-collections, considering that the GPS records may be partly missing (a practical issue). We then use conditional random field (CRF) models to exploit the correlation between photos based on (1) time-location constraints and (2) the relationship between collection-level annotation (i.e., events) and image-level annotation (i.e., scenes). With the introduction of such a multi-level annotation hierarchy, our system addresses the problem of annotating consumer photo collections that requires a more hierarchical description of the customers’ activities than do the simpler image annotation tasks. The efficacy of the proposed system is validated using a geotagged customer photo collection database, which consists of over 100 folders and is labeled for 12 events and 12 scenes.
Semantic-based indexing of fetal anatomies from 3-D ultrasound data using global/semi-local context and sequential sampling
Authors: Gustavo Carneiro 0001, Fernando Amat, Bogdan Georgescu, Sara Good, Dorin Comaniciu
Venue: CVPR
Year: 2008

The use of 3-D ultrasound data has several advantages over 2-D ultrasound for fetal biometric measurements, such as considerable decrease in the examination time, possibility of post-exam data processing by experts and the ability to produce 2-D views of the fetal anatomies in orientations that cannot be seen in common 2-D ultrasound exams. However, the search for standardized planes and the precise localization of fetal anatomies in ultrasound volumes are hard and time consuming processes even for expert physicians and sonographers. The relative low resolution in ultrasound volumes, small size of fetus anatomies and inter-volume position, orientation and size variability make this localization problem even more challenging. In order to make the plane search and fetal anatomy localization problems completely automatic, we introduce a novel principled probabilistic model that combines discriminative and generative classifiers with contextual information and sequential sampling. We implement a system based on this model, where the user queries consist of semantic keywords that represent anatomical structures of interest. After queried, the system automatically displays standardized planes and produces biometric measurements of the fetal anatomies. Experimental results on a held-out test set show that the automatic measurements are within the inter-user variability of expert users. It resolves for position, orientation and size of three different anatomies in less than 10 seconds in a dual-core computer running at 1.7 GHz.
Generalised blurring mean-shift algorithms for nonparametric clustering
Authors: Miguel Á. Carreira-Perpiñán
Venue: CVPR
Year: 2008

Gaussian blurring mean-shift (GBMS) is a nonparametric clustering algorithm, having a single bandwidth parameter that controls the number of clusters. The algorithm iteratively shrinks the data set under the application of a mean-shift update, stops in just a few iterations and yields excellent clusterings. We propose several families of generalised GBMS (GGBMS) algorithms based on explicit, implicit and exponential updates, and depending on a step-size parameter. We give conditions on the step size for the convergence of these algorithms and show that the convergence rate for Gaussian clusters ranges from sublinear to linear, cubic and even higher order depending on the update and step size. We show that the algorithms are related to spectral clustering if using a random-walk matrix with modified eigenvalues and updated after each iteration, and show the relation with methods developed for surface smoothing in the computer graphics literature. Detailed experiments in toy problems and image segmentation show that, while all the GGBMS algorithms can achieve essentially the same result (for appropriate settings of the bandwidth and step size), they significantly differ in runtime, with slightly over-relaxed explicit updates being fastest in practice.
Dimensionality reduction by unsupervised regression
Authors: Miguel Á. Carreira-Perpiñán, Zhengdong Lu
Venue: CVPR
Year: 2008

We consider the problem of dimensionality reduction, where given high-dimensional data we want to estimate two mappings: from high to low dimension (dimensionality reduction) and from low to high dimension (reconstruction). We adopt an unsupervised regression point of view by introducing the unknown low-dimensional coordinates of the data as parameters, and formulate a regularised objective functional of the mappings and low-dimensional coordinates. Alternating minimisation of this functional is straightforward: for fixed low-dimensional coordinates, the mappings have a unique solution; and for fixed mappings, the coordinates can be obtained by finite-dimensional non-linear minimisation. Besides, the coordinates can be initialised to the output of a spectral method such as Laplacian eigenmaps. The model generalises PCA and several recent methods that learn one of the two mappings but not both; and, unlike spectral methods, our model provides out-of-sample mappings by construction. Experiments with toy and real-world problems show that the model is able to learn mappings for convoluted manifolds, avoiding bad local optima that plague other methods.
Globally optimal bilinear programming for computer vision applications
Authors: Manmohan Krishna Chandraker, David J. Kriegman
Venue: CVPR
Year: 2008

We present a practical algorithm that provably achieves the global optimum for a class of bilinear programs commonly arising in computer vision applications. Our approach relies on constructing tight convex relaxations of the objective function and minimizing it in a branch and bound framework. A key contribution of the paper is a novel, provably convergent branching strategy that allows us to solve large-scale problems by restricting the branching dimensions to just one set of variables constituting the bilinearity. Experiments with synthetic and real data validate our claims of optimality, speed and convergence. We contrast the optimality of our solutions with those obtained by a traditional singular value decomposition approach. Among several potential applications, we discuss two: exemplar-based face reconstruction and non-rigid structure from motion. In both cases, we compute the best bilinear fit that represents a shape, observed in a single image from an arbitrary viewpoint, as a combination of the elements of a basis.
Regularizing 3D medial axis using medial scaffold transforms
Authors: Ming-Ching Chang, Benjamin B. Kimia
Venue: CVPR
Year: 2008

This paper addresses a key bottleneck in the use of the 3D medial axis (MA) representation, namely, how the complex MA structure can be regularized so that similar, within-category 3D shapes yield similar 3D MA that are distinct from the non-category shapes. We rely on previous work which (i) constructs a hierarchical MA hypergraph, the medial scaffold (MS), and (ii) the theoretical classification of the instabilities of this structure, or transitions (sudden topological changes due to a small perturbation). The shapes at transition point are degenerate. Our approach is to recognize the transitions which are close-by to a given shape and transform the shape to this transition point, and repeat until no close-by transitions exists. This move towards degeneracy is the basis of simplification of shape. We derive 11 transforms from 7 transitions and follow a greedy scheme in applying the transform. The results show that the simplified MA preserves with-in-category similarity, thus indicating its potential use in various applications including shape analysis, manipulation, and matching.
Improving local learning for object categorization by exploring the effects of ranking
Authors: Tien-Lung Chang, Tyng-Luh Liu, Jen-Hui Chuang
Venue: CVPR
Year: 2008

Local learning for classification is useful in dealing with various vision problems. One key factor for such approaches to be effective is to find good neighbors for the learning procedure. In this work, we describe a novel method to rank neighbors by learning a local distance function, and meanwhile to derive the local distance function by focusing on the high-ranked neighbors. The two aspects of considerations can be elegantly coupled through a well-defined objective function, motivated by a supervised ranking method called P-Norm Push. While the local distance functions are learned independently, they can be reshaped altogether so that their values can be directly compared. We apply the proposed method to the Caltech-101 dataset, and demonstrate the use of proper neighbors can improve the performance of classification techniques based on nearest-neighbor selection.
Hybrid body representation for integrated pose recognition, localization and segmentation
Authors: Cheng Chen, Guoliang Fan
Venue: CVPR
Year: 2008

We propose a hybrid body representation that represents each typical pose by both template-like view information and part-based structural information. Specifically, each body part as well as the whole body are represented by an off-line learned shape model where both region-based and edge-based priors are combined in a coupled shape representation. Part-based spatial priors are represented by a “star” graphical model. This hybrid body representation can synergistically integrate pose recognition, localization and segmentation into one computational flow. Moreover, as an important step for feature extraction and model inference, segmentation is involved in the low-level, mid-level and high-level vision stages, where top-down prior knowledge and bottom-up data processing is well integrated via the proposed hybrid body representation.
An adaptive learning method for target tracking across multiple cameras
Authors: Kuan-Wen Chen, Chih-Chuan Lai, Yi-Ping Hung, Chu-Song Chen
Venue: CVPR
Year: 2008

This paper proposes an adaptive learning method for tracking targets across multiple cameras with disjoint views. Two visual cues are usually employed for tracking targets across cameras: spatio-temporal cue and appearance cue. To learn the relationships among cameras, traditional methods used batch-learning procedures or hand-labeled correspondence, which can work well only within a short period of time. In this paper, we propose an unsupervised method which learns both spatio-temporal relationships and appearance relationships adaptively and can be applied to long-term monitoring. Our method performs target tracking across multiple cameras while also considering the environment changes, such as sudden lighting changes. Also, we improve the estimation of spatio-temporal relationships by using the prior knowledge of camera network topology.
Sketching in the air: A vision-based system for 3D object design
Authors: Yu Chen 0009, Jianzhuang Liu, Xiaoou Tang
Venue: CVPR
Year: 2008

3D object design has many applications including flexible 3D sketch input in CAD, computer game, webpage content design, image based object modeling, and 3D object retrieval. Most current 3D object design tools work on a 2D drawing plane such as computer screen or tablet, which is often inflexible with one dimension lost. On the other hand, virtual reality based methods have the drawbacks that there are awkward devices worn by the user and the virtual environment systems are expensive. In this paper, we propose a novel vision-based approach to 3D object design. Our system consists of a PC, a camera, and a mirror. We use the camera and mirror to track a wand so that the user can design 3D objects by sketching in 3D free space directly with out having to wear any cumbersome devices. A number of new techniques are developed for working in this system, including input of object wireframes, gestures for editing and drawing objects, and optimization-based planar and curved surface generation. Our system provides designers a new user interface for designing 3D objects conveniently.
The statistical modelling of fingerprint minutiae distribution with implications for fingerprint individuality studies
Authors: Jiansheng Chen 0001, Yiu Sang Moon
Venue: CVPR
Year: 2008

The spatial distribution of fingerprint minutiae is a core problem in the fingerprint individuality study, the cornerstone of the fingerprint authentication technology. Previously, the assumption in most research that minutiae distribution is random has been proved to be inaccurate and may lead to significant overestimates of fingerprint uniqueness. In this paper, we propose a stochastic model for describing and simulating fingerprint minutiae patterns. Through coupling a pair potential Markov point process with a thinned process, this model successfully depicts the complex statistical behavior of fingerprint minutiae. Parameters of this model can be determined by nonlinear minimization. Furthermore, experiment results show that the statistical properties of our proposed model dovetails nicely with real minutiae data in terms of the false fingerprint correspondence probability. Such evidences indicate that the proposed model is a more accurate foundation for minutiae based fingerprint individuality studies as well as the artificial fingerprint synthesis when compared to the model of random distribution.