OpenRaiser/Intern-Atlas huggingface dataset:
Grassmann discriminant analysis: a unifying view on subspace-based learning
Authors: Jihun Ham, Daniel D. Lee
Venue: Conference ICML 2008
Year: 2008

In this paper we propose a discriminant learning framework for problems in which data consist of linear subspaces instead of vectors. By treating subspaces as basic elements, we can make learning algorithms adapt naturally to the problems with linear invariant structures. We propose a unifying view on the subspace-based learning method by formulating the problems on the Grassmann manifold, which is the set of fixed-dimensional linear subspaces of a Euclidean space. Previous methods on the problem typically adopt an inconsistent strategy: feature extraction is performed in the Euclidean space while non-Euclidean distances are used. In our approach, we treat each sub-space as a point in the Grassmann space, and perform feature extraction and classification in the same space. We show feasibility of the approach by using the Grassmann kernel functions such as the Projection kernel and the Binet-Cauchy kernel. Experiments with real image databases show that the proposed method performs well compared with state-of-the-art algorithms.
Training linear svms in linear time
Authors: Thorsten Joachims
Venue: Conference KDD 2006
Year: 2006

Linear Support Vector Machines (SVMs) have become one of the most prominent machine learning techniques for high-dimensional sparse data commonly encountered in applications like text classification, word-sense disambiguation, and drug design. These applications involve a large number of examples n as well as a large number of features N, while each example has only s
Masked FFT registration
Authors: Dirk Ryan Padfield
Venue: Conference CVPR 2010
Year: 2010

Registration is a ubiquitous task for image analysis applications. Generally, the requirements of registration algorithms include fast computation and large capture range. For these purposes, registration in the Fourier domain using normalized cross correlation is well suited and has been extensively studied in the literature. Another common requirement is masking, which is necessary for applications where certain regions of the image that would adversely affect the registration result should be ignored. To address these requirements, we have derived a mathematical model that describes an exact form for embedding the masking step fully into the Fourier domain. We also provide an extension of this masked registration approach from simple translation to also include rotation and scale. We demonstrate the computational efficiency of our algorithm and validate its correctness on several synthetic images and real ultrasound images. Our framework enables fast, global, parameter-free registration of images with masked regions.
Alignment by maximization of mutual information
Authors: Paul A. Viola, William M. Wells III
Venue: Conference ICCV 1995
Year: 1995

A new information-theoretic approach is presented for finding the pose of an object in an image. The technique does not require information about the surface properties of the object, besides its shape, and is robust with respect to variations of illumination. In our derivation, few assumptions are made about the nature of the imaging process. As a result, the algorithms are quite general and can foreseeably be used in a wide variety of imaging situations. Experiments are presented that demonstrate the approach in registering magnetic resonance images, aligning a complex 3D object model to real scenes including clutter and occlusion, tracking a human head in a video sequence and aligning a view-based 2D object model to real images. The method is based on a formulation of the mutual information between the model and the image. As applied in this paper, the technique is intensity-based, rather than feature-based. It works well in domains where edge or gradient-magnitude based methods have difficulty, yet it is more robust then traditional correlation. Additionally, it has an efficient implementation that is based on stochastic approximation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Peet: Prototype embedding and embedding transition for matching vehicles over disparate viewpoints
Authors: Yanlin Guo, Ying Shan, Harpreet S. Sawhney, Rakesh Kumar 0001
Venue: Conference CVPR 2007
Year: 2007

This paper presents a novel framework, prototype embedding and embedding transition (PEET), for matching objects, especially vehicles, that undergo drastic pose, appearance, and even modality changes. The problem of matching objects seen under drastic variations is reduced to matching embeddings of object appearances instead of matching the object images directly. An object appearance is first embedded in the space of a representative set of model prototypes (prototype embedding (PE)). Objects captured at disparate temporal and spatial sites are embedded in the space of prototypes that are rendered with the pose of the cameras at the respective sites. Low dimensional embedding vectors are subsequently matched. A significant feature of our approach is that no mapping function is needed to compute the distance between embedding vectors extracted from objects viewed from disparate pose and appearance changes, instead, an embedding transition (ET) scheme is utilized to implicitly realize the complex and non-linear mapping with high accuracy. The heterogeneous nature of matching between high-resolution and low-resolution image objects in PEET is discussed, and an unsupervised learning scheme based on the exploitation of the heterogeneous nature is developed to improve the overall matching performance of mixed resolution objects. The proposed approach has been applied to vehicular object classification and query application, and the extensive experimental results demonstrate the efficacy and versatility of the PEET framework.
Using particles to track varying numbers of interacting people
Authors: Kevin Smith 0001, Daniel Gatica-Perez, Jean-Marc Odobez
Venue: Conference CVPR 2005
Year: 2005

In this paper, we present a Bayesian framework for the fully automatic tracking of a variable number of interacting targets using a fixed camera. This framework uses a joint multi-object state-space formulation and a trans-dimensional Markov Chain Monte Carlo (MCMC) particle filter to recursively estimates the multi-object configuration and efficiently search the state-space. We also define a global observation model comprised of color and binary measurements capable of discriminating between different numbers of objects in the scene. We present results which show that our method is capable of tracking varying numbers of people through several challenging real-world tracking situations such as full/partial occlusion and entering/leaving the scene.
Abnormal detection using interaction energy potentials
Authors: Xinyi Cui, Qingshan Liu 0001, Mingchen Gao, Dimitris N. Metaxas
Venue: Conference CVPR 2011
Year: 2011

A new method is proposed to detect abnormal behaviors in human group activities. This approach effectively models group activities based on social behavior analysis. Different from previous work that uses independent local features, our method explores the relationships between the current behavior state of a subject and its actions. An interaction energy potential function is proposed to represent the current behavior state of a subject, and velocity is used as its actions. Our method does not depend on human detection or segmentation, so it is robust to detection errors. Instead, tracked spatio-temporal interest points are able to provide a good estimation of modeling group interaction. SVM is used to find abnormal events. We evaluate our algorithm in two datasets: UMN and BEHAVE. Experimental results show its promising performance against the state-of-art methods.
Unsupervised joint alignment of complex images
Authors: Gary B. Huang, Vidit Jain, Erik G. Learned-Miller
Venue: Conference ICCV 2007
Year: 2007

Many recognition algorithms depend on careful positioning of an object into a canonical pose, so the position of features relative to a fixed coordinate system can be examined. Currently, this positioning is done either manually or by training a class-specialized learning algorithm with samples of the class that have been hand-labeled with parts or poses. In this paper, we describe a novel method to achieve this positioning using poorly aligned examples of a class with no additional labeling. Given a set of unaligned examplars of a class, such as faces, we automatically build an alignment mechanism, without any additional labeling of parts or poses in the data set. Using this alignment mechanism, new members of the class, such as faces resulting from a face detector, can be precisely aligned for the recognition process. Our alignment method improves performance on a face recognition task, both over unaligned images and over images aligned with a face alignment algorithm specifically developed for and trained on hand-labeled face images. We also demonstrate its use on an entirely different class of objects (cars), again without providing any information about parts or pose to the learning algorithm.
Predicting query performance
Authors: Stephen Cronen-Townsend, Yun Zhou, W. Bruce Croft
Venue: Conference SIGIR 2002
Year: 2002

We develop a method for predicting query performance by computing the relative entropy between a query language model and the corresponding collection language model. The resulting clarity score measures the coherence of the language usage in documents whose models are likely to generate the query. We suggest that clarity scores measure the ambiguity of a query with respect to a collection of documents and show that they correlate positively with average precision in a variety of TREC test sets. Thus, the clarity score may be used to identify ine#ective queries, on average, without relevance information. We develop an algorithm for automatically setting the clarity score threshold between predicted poorly-performing queries and acceptable queries and validate it using TREC data. In particular, we compare the automatic thresholds to optimum thresholds and also check how frequently results as good are achieved in sampling experiments that randomly assign queries to the two classes.
Sparse representation or collaborative representation: Which helps face recognition?
Authors: Lei Zhang 0006, Meng Yang 0001, Xiangchu Feng
Venue: Conference ICCV 2011
Year: 2011

As a recently proposed technique, sparse representation based classification (SRC) has been widely used for face recognition (FR). SRC first codes a testing sample as a sparse linear combination of all the training samples, and then classifies the testing sample by evaluating which class leads to the minimum representation error. While the importance of sparsity is much emphasized in SRC and many related works, the use of collaborative representation (CR) in SRC is ignored by most literature. However, is it really the l <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> -norm sparsity that improves the FR accuracy? This paper devotes to analyze the working mechanism of SRC, and indicates that it is the CR but not the l1-norm sparsity that makes SRC powerful for face classification. Consequently, we propose a very simple yet much more efficient face classification scheme, namely CR based classification with regularized least square (CRC_RLS). The extensive experiments clearly show that CRC_RLS has very competitive classification results, while it has significantly less complexity than SRC.
Rankboost with l1 regularization for facial expression recognition and intensity estimation
Authors: Peng Yang 0001, Qingshan Liu 0001, Dimitris N. Metaxas
Venue: Conference ICCV 2009
Year: 2009

Most previous facial expression analysis works only focused on expression recognition. In this paper, we propose a novel framework of facial expression analysis based on the ranking model. Different from previous works, it not only can do facial expression recognition, but also can estimate the intensity of facial expression, which is very important to further understand human emotion. Although it is hard to label expression intensity quantitatively, the ordinal relationship in temporal domain is actually a good relative measurement. Based on this observation, we convert the problem of intensity estimation to a ranking problem, which is modeled by the RankBoost. The output ranking score can be directly used for intensity estimation, and we also extend the ranking function for expression recognition. To further improve the performance, we propose to introduce l <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> based regularization into the Rankboost. Experiments on the Cohn-Kanade database show that the proposed method has a promising performance compared to the state-of-the-art.
Image retrieval via probabilistic hypergraph ranking
Authors: Yuchi Huang, Qingshan Liu 0001, Shaoting Zhang 0001, Dimitris N. Metaxas
Venue: Conference CVPR 2010
Year: 2010

In this paper, we propose a new transductive learning framework for image retrieval, in which images are taken as vertices in a weighted hypergraph and the task of image search is formulated as the problem of hypergraph ranking. Based on the similarity matrix computed from various feature descriptors, we take each image as a `centroid' vertex and form a hyperedge by a centroid and its k-nearest neighbors. To further exploit the correlation information among images, we propose a probabilistic hypergraph, which assigns each vertex v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> to a hyperedge e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> in a probabilistic way. In the incidence structure of a probabilistic hypergraph, we describe both the higher order grouping information and the affinity relationship between vertices within each hy-peredge. After feedback images are provided, our retrieval system ranks image labels by a transductive inference approach, which tends to assign the same label to vertices that share many incidental hyperedges, with the constraints that predicted labels of feedback images should be similar to their initial labels. We compare the proposed method to several other methods and its effectiveness is demonstrated by extensive experiments on Corel5K, the Scene dataset and Caltech 101.
Sparse reconstruction cost for abnormal event detection
Authors: Yang Cong, Junsong Yuan 0001, Ji Liu 0002
Venue: Conference CVPR 2011
Year: 2011

We propose to detect abnormal events via a sparse reconstruction over the normal bases. Given an over-complete normal basis set (e.g., an image sequence or a collection of local spatio-temporal patches), we introduce the sparse reconstruction cost (SRC) over the normal dictionary to measure the normalness of the testing sample. To condense the size of the dictionary, a novel dictionary selection method is designed with sparsity consistency constraint. By introducing the prior weight of each basis during sparse reconstruction, the proposed SRC is more robust compared to other outlier detection criteria. Our method provides a unified solution to detect both local abnormal events (LAE) and global abnormal events (GAE). We further extend it to support online abnormal event detection by updating the dictionary incrementally. Experiments on three benchmark datasets and the comparison to the state-of-the-art methods validate the advantages of our algorithm.
Saliency detection: A spectral residual approach
Authors: Xiaodi Hou, Liqing Zhang 0001
Venue: Conference CVPR 2007
Year: 2007

The ability of human visual system to detect visual saliency is extraordinarily fast and reliable. However, computational modeling of this basic intelligent behavior still remains a challenge. This paper presents a simple method for the visual saliency detection. Our model is independent of features, categories, or other forms of prior knowledge of the objects. By analyzing the log-spectrum of an input image, we extract the spectral residual of an image in spectral domain, and propose a fast method to construct the corresponding saliency map in spatial domain. We test this model on both natural pictures and artificial images such as psychological patterns. The result indicate fast and robust saliency detection of our method.
Deriving intrinsic images from image sequences
Authors: Yair Weiss
Venue: Conference ICCV 2001
Year: 2001

Intrinsic images are a useful midlevel description of scenes proposed by H.G. Barrow and J.M. Tenenbaum (1978). An image is de-composed into two images: a reflectance image and an illumination image. Finding such a decomposition remains a difficult problem in computer vision. We focus on a slightly, easier problem: given a sequence of T images where the reflectance is constant and the illumination changes, can we recover T illumination images and a single reflectance image? We show that this problem is still imposed and suggest approaching it as a maximum-likelihood estimation problem. Following recent work on the statistics of natural images, we use a prior that assumes that illumination images will give rise to sparse filter outputs. We show that this leads to a simple, novel algorithm for recovering reflectance images. We illustrate the algorithm's performance on real and synthetic image sequences.
Global connectivity potentials for random field models
Authors: Sebastian Nowozin, Christoph H. Lampert
Venue: Conference CVPR 2009
Year: 2009

Markov random field (MRF, CRF) models are popular in computer vision. However, in order to be computationally tractable they are limited to incorporate only local interactions and cannot model global properties, such as connectedness, which is a potentially useful high-level prior for object segmentation. In this work, we overcome this limitation by deriving a potential function that enforces the output labeling to be connected and that can naturally be used in the framework of recent MAP-MRF LP relaxations. Using techniques from polyhedral combinatorics, we show that a provably tight approximation to the MAP solution of the resulting MRF can still be found efficiently by solving a sequence of max-flow problems. The efficiency of the inference procedure also allows us to learn the parameters of a MRF with global connectivity potentials by means of a cutting plane algorithm. We experimentally evaluate our algorithm on both synthetic data and on the challenging segmentation task of the PASCAL VOC 2008 data set. We show that in both cases the addition of a connectedness prior significantly reduces the segmentation error.
The bayesian group-lasso for analyzing contingency tables
Authors: Sudhir Raman, Thomas J. Fuchs, Peter J. Wild, Edgar Dahl, Volker Roth 0001
Venue: Conference ICML 2009
Year: 2009

Group-Lasso estimators, useful in many applications, suffer from lack of meaningful variance estimates for regression coefficients. To overcome such problems, we propose a full Bayesian treatment of the Group-Lasso, extending the standard Bayesian Lasso, using hierarchical expansion. The method is then applied to Poisson models for contingency tables using a highly efficient MCMC algorithm. The simulated experiments validate the performance of this method on artificial datasets with known ground-truth. When applied to a breast cancer dataset, the method demonstrates the capability of identifying the differences in interactions patterns of marker proteins between different patient groups.
SVM optimization: inverse dependence on training set size
Authors: Shai Shalev-Shwartz, Nathan Srebro
Venue: Conference ICML 2008
Year: 2008

We discuss how the runtime of SVM optimization should decrease as the size of the training data increases. We present theoretical and empirical results demonstrating how a simple subgradient descent approach indeed displays such behavior, at least for linear kernels.
Local intensity order pattern for feature description
Authors: Zhenhua Wang 0002, Bin Fan 0001, Fuchao Wu
Venue: Conference ICCV 2011
Year: 2011

This paper presents a novel method for feature description based on intensity order. Specifically, a Local Intensity Order Pattern(LIOP) is proposed to encode the local ordinal information of each pixel and the overall ordinal information is used to divide the local patch into subregions which are used for accumulating the LIOPs respectively. Therefore, both local and overall intensity ordinal information of the local patch are captured by the proposed LIOP descriptor so as to make it a highly discriminative descriptor. It is shown that the proposed descriptor is not only invariant to monotonic intensity changes and image rotation but also robust to many other geometric and photometric transformations such as viewpoint change, image blur and JEPG compression. The proposed descriptor has been evaluated on the standard Oxford dataset and four additional image pairs with complex illumination changes. The experimental results show that the proposed descriptor obtains a significant improvement over the existing state-of-the-art descriptors.
Mode-seeking by medoidshifts
Authors: Yaser Sheikh, Erum A. Khan, Takeo Kanade
Venue: Conference ICCV 2007
Year: 2007

We present a nonparametric mode-seeking algorithm, called medoidshift, based on approximating the local gradient using a weighted estimate of medoids. Like meanshift, medoidshift clustering automatically computes the number of clusters and the data does not have to be linearly separable. Unlike meanshift, the proposed algorithm does not require the definition of a mean. This property allows medoidshift to find modes even when only a distance measure between samples is defined. In this sense, the relationship between the medoidshift algorithm and the meanshift algorithm is similar to the relationship between the k-medoids and the k-means algorithms. We show that medoidshifts can also be used for incremental clustering of growing datasets by recycling previous computations. We present experimental results using medoidshift for image segmentation, incremental clustering for shot segmentation and clustering on nonlinearly separable data.
The application of adaboost for distributed, scalable and on-line learning
Authors: Wei Fan, Salvatore J. Stolfo, Junxin Zhang
Venue: Conference KDD 1999
Year: 1999

1 Introduction Learning from very large and distributed databases imposes major performance challenges for data mining. Many databases have grown too large to fit into main memory. Learning a monolithic classifier will be very slow since it requires all data be held in main memory. Some databases are inherently distributed and cannot be brought into a single site for a variety of reasons. It is very hard to learn a single classifier under these constraints. One such application is to learn a fraud detection model from different participating credit card companies whose datasets are huge and strictly distributed. Yet there are some databases that have large amounts of new data available periodically or in real time. To re-learn a new model of the whole data set each time an increment is provided is both expensive and inefficient.