OpenRaiser/Intern-Atlas huggingface dataset:
A Two-Stage Level Set Evolution Scheme for Man-Made Objects Detection in Aerial Images
Authors: Guo Cao, Xin Yang 0007, Zhihong Mao
Venue: CVPR
Year: 2005

A novel two-stage level set evolution method for detecting man-made objects in aerial images is described. The method is based on a modified Mumford-Shah model and it uses a two-stage curve evolution strategy to get a preferable detection. It applies fractal error metric, developed by Cooper, et al. (1994) at the first curve evolution stage and adds additional constraint texture edge descriptor that is defined by using DCT (discrete cosine transform) coefficients on the image at the next stage. Man-made objects and natural areas are optimally differentiated by evolving the partial differential equation. The method artfully avoids selecting a threshold to separate the fractal error image, while an improper threshold often results in great segmentation errors. Experiments of the segmentation show that the proposed method is efficient.
The Distinctiveness, Detectability, and Robustness of Local Image Features
Authors: Gustavo Carneiro 0001, Allan D. Jepson
Venue: CVPR
Year: 2005

We introduce a new method that characterizes typical local image features (e.g., SIFT, phase feature) in terms of their distinctiveness, detectability, and robustness to image deformations. This is useful for the task of classifying local image features in terms of those three properties. The importance of this classification process for a recognition system using local features is as follows: a) reduce the recognition time due to a smaller number of features present in the test image and in the database of model features; b) improve the recognition accuracy since only the most useful features for the recognition task are kept in the model database; and c) increase the scalability of the recognition system given the smaller number of features per model. A discriminant classifier is trained to select well behaved feature points. A regression network is then trained to provide quantitative models of the detection distributions for each selected feature point. It is important to note that both the classifier and the regression network use image data alone as their input. Experimental results show that the use of these trained networks not only improves the performance of our recognition system, but it also significantly reduces the computation time for the recognition process.
Formulating Semantic Image Annotation as a Supervised Learning Problem
Authors: Gustavo Carneiro 0001, Nuno Vasconcelos
Venue: CVPR
Year: 2005

We introduce a new method to automatically annotate and retrieve images using a vocabulary of image semantics. The novel contributions include a discriminant formulation of the problem, a multiple instance learning solution that enables the estimation of concept probability distributions without prior image segmentation, and a hierarchical description of the density of each image class that enables very efficient training. Compared to current methods of image annotation and retrieval, the one now proposed has significantly smaller time complexity and better recognition performance. Specifically, its recognition complexity is O(C/spl times/R), where C is the number of classes (or image annotations) and R is the number of image regions, while the best results in the literature have complexity O(T/spl times/R), where T is the number of training images. Since the number of classes grows substantially slower than that of training images, the proposed method scales better during training, and processes test images faster This is illustrated through comparisons in terms of complexity, time, and recognition performance with current state-of-the-art methods.
Unsupervised Learning in Radiology Using Novel Latent Variable Models
Authors: Luke Carrivick, Sanjay Prabhu, Paul Goddard, Jonathan Rossiter
Venue: CVPR
Year: 2005

In this paper we compare a variety of unsupervised probabilistic models used to represent a data set consisting of textual and image information. We show that those based on latent Dirichlet allocation (LDA) out perform traditional mixture models in likelihood comparison. The data set is taken from radiology; a combination of medical images and consultants reports. The task of learning to classify individual tissue, or disease types, requires expert hand labeled data. This is both: expensive to produce and prone to inconsistencies in labeling. Here we present methods that require no hand labeling and also automatically discover sub-types of disease. The learnt models can be used for both prediction and classification of new unseen data.
A Hybrid Graphical Model for Robust Feature Extraction from Video
Authors: Ali Taylan Cemgil, Wojciech Zajdel, Ben J. A. Kröse
Venue: CVPR
Year: 2005

We consider a visual scene analysis scenario where objects (e.g. people, cars) pass through the viewing field of a static camera and need to be detected and segmented from the background. For this purpose, we introduce a hybrid dynamic Bayesian network and derive an expectation propagation (EP) algorithm for robust estimation of object shapes and appearance statistics. We demonstrate the viability of the approximation on an object detection task from real videos, where objects' smooth shapes are segmented from the background. The model is readily extendible to multi-object multi-camera scenarios and can be coupled in a transparent and consistent way with a hierarchical model for object identification under uncertainty.
Level Set Based Shape Prior Segmentation
Authors: Tony F. Chan, Wei Zhu 0003
Venue: CVPR
Year: 2005

We propose a level set based variational approach that incorporates shape priors into Chan-Vese's model for the shape prior segmentation problem. In our model, besides the level set function for segmentation, as in Cremers' work, we introduce another labelling level set function to indicate the regions on which the prior shape should be compared. Our model can segment an object, whose shape is similar to the given prior shape, from a background where there are several objects. Moreover, we provide a proof for a fast solution principle, which was mentioned by F. Gibou et al., and similar to the one proposed in [B. Song et al., (2002)], for minimizing Chan-Vese's segmentation model without length term. We extend the principle to the minimization of our prescribed functionals.
Using Coupled Subspace Models for Recovery of Reflectance Spectra from Airborne Images
Authors: Kartik Chandra, Glenn Healey
Venue: CVPR
Year: 2005

The spectral radiance measured by an airborne sensor is dependent on the spectral reflectance of the ground material, the orientation of the material surface, and the atmospheric and illumination conditions. We present a nonlinear algorithm for estimating surface spectral reflectance of a surface on the ground from the spectral radiance measured by an airborne sensor. The nonlinear separation algorithm uses a low-dimensional subspace model for the reflectance spectra. The algorithm also considers the inter-dependence of the path radiance and illumination spectra by using a coupled subspace model. We have applied the algorithm to a large set of 0.4-1.74 micron sensor radiance spectra. We have examined the use of the recovered reflectance vectors for material identification over a database of materials from the US geological Survey (USGS) library. We also extend the nonlinear algorithm to estimate the reflectance spectra of materials having varying orientations. We have applied the algorithm to 0.42-1.74 micron sensor radiance spectra in digital imaging and remote sensing image generation (DIRSIG) model scenes that contain 3D objects.
Real-Time Tracking with Multiple Cues by Set Theoretic Random Search
Authors: Cheng Chang, Rashid Ansari
Venue: CVPR
Year: 2005

Conventional treatment of visual tracking has been to optimize an objective function in a probabilistic framework. In this formulation, efficient algorithms employing simple prior distributions are usually insufficient to handle clutters (e.g., Kalman filter). On the other hand, distributions that are complex enough to incorporate all a priori knowledge can make the problem computationally intractable (e.g., particle filters (PF)). This paper proposes a new formulation of visual tracking where every piece of information, be it from a priori knowledge or observed data, is represented by a set in the solution space and the intersection of these sets, the feasibility set, represents all acceptable solutions. Based on this formulation, we propose an algorithm whose objective is to find a solution in the feasibility set. We show that this set theoretic tracking algorithm performs effective face tracking and is computationally more efficient than standard PF-based tracking.
Multiple Object Tracking with Kernel Particle Filter
Authors: Cheng Chang, Rashid Ansari, Ashfaq A. Khokhar
Venue: CVPR
Year: 2005

A new particle filter, kernel particle filter (KPF), is proposed for visual tracking for multiple objects in image sequences. The KPF invokes kernels to form a continuous estimate of the posterior density function and allocates particles based on the gradient derived from the kernel density estimate. A data association technique is also proposed to resolve the motion correspondence ambiguities that arise when multiple objects are present. The data association technique introduces minimal amount of computation by making use of the intermediate results obtained in particle allocation. We show that KPF performs robust multiple object tracking with improved sampling efficiency.
Appearance-Guided Particle Filtering for Articulated Hand Tracking
Authors: Wen-Yan Chang, Chu-Song Chen, Yi-Ping Hung
Venue: CVPR
Year: 2005

We propose a model-based tracking method, called appearance-guided particle filtering (AGPF), which integrates both sequential motion transition information and appearance information. A probability propagation model is derived from a Bayesian formulation for this framework, and a sequential Monte Carlo method is introduced for its realization. We apply the proposed method to articulated hand tracking, and show that it performs better than methods that only use either sequential motion transition information or only use appearance information.
A Bayesian Approach to Unsupervised Feature Selection and Density Estimation Using Expectation Propagation
Authors: Shaorong Chang, Nilanjan Dasgupta, Lawrence Carin
Venue: CVPR
Year: 2005

We propose an approximate Bayesian approach for unsupervised feature selection and density estimation, where the importance of the features for clustering is used as the measure for feature selection. Traditional maximum-likelihood (ML) model-parameter optimization schemes estimate the feature saliencies for a fixed model structure (i.e., a fixed number of clusters). In practice, the number of clusters present in the data for mixture-based modeling is unknown. In an ML framework, the number of clusters typically needs to be ascertained prior to estimating the feature saliencies. We propose a density estimation scheme that addresses model complexity (number of clusters present) and model-parameter estimation (feature saliencies) in a single optimization framework. The approximate Bayesian approach presented here, based on the expectation propagation method, obtains a full posterior distribution on the saliency of the features, along with full posterior distribution of other model parameters (including the number of clusters) that represent the underlying statistics of the data. The performance of the algorithm, is analyzed based on its ability to identify the features salient for clustering the multivariate data.
Learning Feature Distance Measures for Image Correspondences
Authors: Xi Chen 0069, Tat-Jen Cham
Venue: CVPR
Year: 2005

Standard but ad hoc measures such as sum-of-squared pixel differences (SSD) are often used when comparing and registering two images that have not been previously observed before. In this paper, we propose a framework to address the problem of learning a parametric feature distance measure to measure the dissimilarity between pairs of images. The method is based on optimizing the parameters of the distance measure in order to minimize correspondence classification errors on training data. Because the learning process involves relative (rather than absolute) visual content between image pairs, the learned distance measure may also be applied to other images with very different visual content. Results on matching classification with a wide variety of image content show that the learned feature distance measure clearly outperforms the standard measures of SSD, chamfer and Bhattacharyya histogram distances.
Tone Reproduction: A Perspective from Luminance-Driven Perceptual Grouping
Authors: Hwann-Tzong Chen, Tyng-Luh Liu, Tien-Lung Chang
Venue: CVPR
Year: 2005

We address the tone reproduction problem by integrating local adaptation with global-contrast consistency. Many previous works have tried to compress high-dynamic-range (HDR) luminances into a displayable range in imitation of the local adaptation mechanism of human eyes. Nevertheless, while the realization of local adaptation is not theoretically defined, exaggerating such effects often causes unnatural global contrasts. We propose a luminance-driven perceptual grouping process to derive a sparse representation of HDR luminances, and use the grouped regions to approximate local properties of luminances. The advantage of incorporating a sparse representation is twofold: We can simulate local adaptation based on region information, and subsequently apply piecewise tone mappings to monotonize the relative brightness over only a few perceptually significant regions. Our experimental results show that the proposed framework gives a good balance in preserving local details and maintaining global contrasts of HDR scenes.
Illumination Normalization for Face Recognition and Uneven Background Correction Using Total Variation Based Image Models
Authors: Terrence Chen, Wotao Yin, Xiang Sean Zhou, Dorin Comaniciu, Thomas S. Huang
Venue: CVPR
Year: 2005

We present a new algorithm for illumination normalization and uneven background correction in images, utilizing the recently proposed TV+L/sup 1/ model: minimizing the total variation of the output cartoon while subject to an L/sup 1/-norm fidelity term. We give intuitive proofs of its main advantages, including the well-known edge preserving capability, minimal signal distortion, and scale-dependent but intensity-independent foreground extraction. We then propose a novel TV-based quotient image model (TVQI) for illumination normalization, an important preprocessing for face recognition under different lighting conditions. Using this model, we achieve 100% face recognition rate on Yale face database B if the reference images are under good lighting condition and 99.45% if not. These results, compared to the average 65% recognition rate of the quotient image model and the average 95% recognition rate of the more recent self quotient image model, show a clear improvement. In addition, this model requires no training data, no assumption on the light source, and no alignment between different images for illumination normalization. We also present the results of the related applications - uneven background correction for cDNA mic roar ray films and digital microscope images. We believe the proposed works can serve important roles in the related fields.
MER-DIMES: A Planetary Landing Application of Computer Vision
Authors: Yang Cheng, Andrew E. Johnson 0002, Larry H. Matthies
Venue: CVPR
Year: 2005

During the Mars Exploration Rover (MER) landings, the descent image motion estimation system (DIMES) was used for horizontal velocity estimation. The DIMES algorithm combined measurements from a descent camera, a radar altimeter, and an inertial measurement unit. To deal with large changes in scale and orientation between descent images, the algorithm used altitude and attitude measurements to rectify images to a level ground plane. Feature selection and tracking were employed in the rectified images to compute the horizontal motion between images. Differences of consecutive motion estimates were then compared to inertial measurements to verify correct feature tracking. DIMES combined sensor data from multiple sources in a novel way to create a low-cost, robust, and computationally efficient velocity estimation solution, and DIMES was the first use of computer vision to control a spacecraft during planetary landing. This paper presents the detailed implementation of the DIMES algorithm and the results from the two landings on Mars.
Video Epitomes
Authors: Vincent Cheung, Brendan J. Frey, Nebojsa Jojic
Venue: CVPR
Year: 2005

Recently, "epitomes" were introduced as patch-based probability models that are learned by compiling together a large number of examples of patches from input images. In this paper, we describe how epitomes can be used to model video data and we describe significant computational speedups that can be incorporated into the epitome inference and learning algorithm. In the case of videos, epitomes are estimated so as to model most of the small space-time cubes from the input data. Then, the epitome can be used for various modeling and reconstruction tasks, of which we show results for video super-resolution, video interpolation, and object removal. Besides computational efficiency, an interesting advantage of the epitome as a representation is that it can be reliably estimated even from videos with large amounts of missing data. We illustrate this ability on the task of reconstructing the dropped frames in video broadcast using only the degraded video.
Learning a Similarity Metric Discriminatively, with Application to Face Verification
Authors: Sumit Chopra, Raia Hadsell, Yann LeCun
Venue: CVPR
Year: 2005

We present a method for training a similarity metric from data. The method can be used for recognition or verification applications where the number of categories is very large and not known during training, and where the number of training samples for a single category is very small. The idea is to learn a function that maps input patterns into a target space such that the L/sub 1/ norm in the target space approximates the "semantic" distance in the input space. The method is applied to a face verification task. The learning process minimizes a discriminative loss function that drives the similarity metric to be small for pairs of faces from the same person, and large for pairs from different persons. The mapping from raw to the target space is a convolutional network whose architecture is designed for robustness to geometric distortions. The system is tested on the Purdue/AR face database which has a very high degree of variability in the pose, lighting, expression, position, and artificial occlusions such as dark glasses and obscuring scarves.
On Modelling Nonlinear Shape-and-Texture Appearance Manifolds
Authors: C. Mario Christoudias, Trevor Darrell
Venue: CVPR
Year: 2005

Statistical shape-and-texture appearance models employ image metamorphosis to form a rich, compact representation of object appearance. They achieve their efficiency by decomposing appearance into simpler shape-and-texture representations. In general, the shape and texture of an object can vary nonlinearly and in this case the conventional shape-and-texture mappings using principle component analysis (PCA) may poorly approximate the true space. In this paper we propose two nonlinear techniques for modelling shape-and-texture appearance manifolds. Our first method uses a mixture of Gaussians in image space to separate the different parts of the shape and texture spaces. A linear shape-and-texture model is defined at each component to form the overall model. Our second approach employs a nearest-neighbor method to find a local set of shapes and images that can be morphed to explain a new input. We test each approach using a speaking-mouth video sequence and compare both approaches to a conventional active appearance model (AAM).
Real-Time Connectivity Constrained Depth Map Computation Using Programmable Graphics Hardware
Authors: Nico Cornelis, Luc Van Gool
Venue: CVPR
Year: 2005

This paper presents a passive depth map computation algorithm which runs entirely on programmable 3D graphics hardware at real-time speed. Previous implementations relied on the use of either mipmapping or correlation windows to increase the robustness of the calculated depth map. These methods, however, are inherently unable to compute the depths for fine 3D structures. To overcome this obstacle we introduce a pixel-based method which incorporates connectivity information between neighboring pixels, while maintaining the performance boost gained by implementing the algorithm on a highly parallelized architecture such as graphics hardware.
Coherent Regions for Concise and Stable Image Description
Authors: Jason J. Corso, Gregory D. Hager
Venue: CVPR
Year: 2005

We present a new method for summarizing images for the purposes of matching and registration. We take the point of view that large, coherent regions in the image provide a concise and stable basis for image description. We develop a new algorithm for image segmentation that operates on several projections (feature spaces) of the image, using kernel-based optimization techniques to locate local extrema of a continuous scale-space of image regions. Descriptors of these image regions and their relative geometry then form the basis of an image description. We present experimental results of these methods applied to the problem of image retrieval. On a moderate sized database, we find that our method performs comparably to two published techniques: Blobworld and SIFT features. However, compared to these techniques two significant advantages of our method are its 1) stability under large changes in the images and 2) its representational efficiency. As a result we argue our proposed method will scale well with larger image sets.
Polarization Multiplexing for Bidirectional Imaging
Authors: Oana G. Cula, Kristin J. Dana, Dinesh K. Pai, Dongsheng Wang
Venue: CVPR
Year: 2005

Our goal is to incorporate polarization in appearance-based modeling in an efficient and meaningful way. Polarization has been used in numerous prior studies for separating diffuse and specular reflectance components, but in this work we show that it also can be used to separate surface reflectance contributions from individual light sources. Our approach is called polarization multiplexing and it has significant impact in appearance modeling and bidirectional imaging where the image as a function of illumination direction is needed. Multiple unknown light sources can illuminate the scene simultaneously, and the individual contributions to the overall surface reflectance can be estimated. To develop the method of polarization multiplexing, we use a relationship between light source direction and intensity modulation. Inverting this transformation enables the individual intensity contributions to be estimated. In addition to polarization multiplexing, we show that phase histograms from the intensity modulations can be used to estimate scene properties including the number of light sources.
Discriminative Training for Object Recognition Using Image Patches
Authors: Thomas Deselaers, Daniel Keysers, Hermann Ney
Venue: CVPR
Year: 2005

We present a method for automatically learning discriminative image patches for the recognition of given object classes. The approach applies discriminative training of log-linear models to image patch histograms. We show that it works well on three tasks and performs significantly better than other methods using the same features. For example, the method decides that patches containing an eye are most important for distinguishing face from background images. The recognition performance is very competitive with error rates presented in other publications. In particular, a new best error rate for the Caltech motorbikes data of 1.5% is achieved.