We consider the problem of self-calibration of a camera whose intrinsic parameters are known, besides the focal length. In the past, algorithms were mainly proposed for estimating two values of the focal length, for t...
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ISBN:
(纸本)0769512720
We consider the problem of self-calibration of a camera whose intrinsic parameters are known, besides the focal length. In the past, algorithms were mainly proposed for estimating two values of the focal length, for two images taken with different zoom. While there exist closed form solutions based on the fundamental matrix, their applicability is limited due to a generic singularity that occurs whenever the optical axes intersect, leading to numerical instabilities in most practical situations. Here, we consider the case of two views with identical focal length. We derive closed form solutions (one quadratic and two linear equations). Their respective singularity conditions are studied analytically and experimental results on their stability are given.
Mapping textured images on smoothly approximated surfaces is often used to conceal the loss of their real, fine-grained relief A limitation of mapping a fixed texture in such cases is that it will only be correct for ...
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ISBN:
(纸本)0769512720
Mapping textured images on smoothly approximated surfaces is often used to conceal the loss of their real, fine-grained relief A limitation of mapping a fixed texture in such cases is that it will only be correct for one viewing and one illumination direction. The presence of geometric surface details causes changes that simple foreshortening and global color scaling cannot model well. Hence, one would like to synthesize different textures for different viewing conditions. A texture model is presented that takes account of viewpoint dependent changes in texture appearance. It is highly compact and avoids copy-and-paste like repetitions. The model is learned from example images taken from different viewpoints. It supports texture synthesis for previously unseen conditions.
We present a novel technique, called image-Based Surface Detail Transfer, to transfer geometric details from one surface to another with simple 2D image operations. The basic observation is that, without knowing its 3...
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ISBN:
(纸本)0769512720
We present a novel technique, called image-Based Surface Detail Transfer, to transfer geometric details from one surface to another with simple 2D image operations. The basic observation is that, without knowing its 3D geometry, geometric details (local deformations) can be extracted from a single image of an object in a way independent of its surface reflectance, and furthermore, these geometric details can be transferred to modify the appearance of other objects directly in images. We show examples including surface detail transfer between real objects, as well as between real and synthesized objects.
An approach for estimating 3D body pose from multiple, uncalibrated views is proposed. First, a mapping from image features to 2D body joint locations is computed using a statistical framework that yields a set of sev...
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ISBN:
(纸本)0769512720
An approach for estimating 3D body pose from multiple, uncalibrated views is proposed. First, a mapping from image features to 2D body joint locations is computed using a statistical framework that yields a set of several body pose hypotheses. The concept of a "virtual camera" is introduced that makes this mapping invariant to translation, image-plane rotation, and scaling of the input. As a consequence, the calibration matrices (intrinsics) of the virtual cameras can be considered completely known, and their poses are known up to a single angular displacement parameter Given pose hypotheses obtained in the multiple virtual camera views, the recovery of 3D body pose and camera relative orientations is formulated as a stochastic optimization problem. An Expectation-Maximization algorithm is derived that can obtain the locally most likely (self-consistent) combination of body pose hypotheses. Performance of the approach is evaluated with synthetic sequences as well as real video sequences of human motion.
The proceedings contains 115 papers from the 2001 ieeecomputersocietyconference on computer Vision and patternrecognition. Topics discussed include: robot homing based on corner tracking;illumination subspace for ...
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The proceedings contains 115 papers from the 2001 ieeecomputersocietyconference on computer Vision and patternrecognition. Topics discussed include: robot homing based on corner tracking;illumination subspace for multibody motion segmentation;feature reduction and hierarchy of classifiers for fast object detection in video images;construction-models for content-based image retrieval;anti-sequences: event detection by frame stacking;event-based analysis of video;on focal length calibration from two views;a bayesian approach to digital matting;image registration by aligning entropies;a self-correcting projector;and image-based detail transfer.
We present a novel approach for tracking locally planar regions in an image sequence and their grouping into larger planar surfaces. The tracker recovers the affine transformation of the region and therefore yields re...
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ISBN:
(纸本)0769512720
We present a novel approach for tracking locally planar regions in an image sequence and their grouping into larger planar surfaces. The tracker recovers the affine transformation of the region and therefore yields reliable point correspondences between frames. Both edges and texture information are exploited in an integrated way, while not requiring the complete region's contour The tracker withstands zoom, out-of-plane rotations, discontinuous motion and changes in illumination conditions while achieving real-time performance for a region. Multiple tracked regions are grouped into disjoint coplanarity classes. We first define a coplanarity score between each pair of regions, based on motion and texture cues. The scores are then analyzed by a clique-partitioning algorithm yielding the coplanarity classes that best fit the data. The method works in the presence of perspective distortions, discontinuous planar surfaces and considerable amounts of measurement noise.
We present two new algorithms for multimodal, dense matching of two images using a variational approach. These algorithms complete and generalise our previous work by treating the case of semi-local energy functionals...
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ISBN:
(纸本)0769512720
We present two new algorithms for multimodal, dense matching of two images using a variational approach. These algorithms complete and generalise our previous work by treating the case of semi-local energy functionals. In brief they are derived from the maximization of two statistical criteria (mutual information and correlation ratio) estimated from corresponding regions around each pixel (or voxel in the 3D case). As a second contribution, we present a result of existence and uniqueness of the solution of the abstract evolution problems associated to these algorithms, as well as those of the corresponding global ones (the proofs could not be reproduced here but can be found in [10]). This is important since it shows the well-posedness of the problems to solve. We finish by showing some applications of our methods to one synthetic and four real examples.
We describe a dataset of several thousand calibrated, geo-referenced, high dynamic range color images, acquired under uncontrolled, variable illumination in an outdoor region spanning hundreds of meters. All image, fe...
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ISBN:
(纸本)0769512720
We describe a dataset of several thousand calibrated, geo-referenced, high dynamic range color images, acquired under uncontrolled, variable illumination in an outdoor region spanning hundreds of meters. All image, feature, calibration, and geo-referencing data are available at http://***/data. Calibrated imagery is of fundamental interest in a wide variety of applications. We have made this data available in the belief that researchers in computer graphics, computer vision, photogrammetry and digital cartography will find it useful in several ways: as a test set for their own algorithms;as a calibrated image set for applications such as image-based rendering, metric 3D reconstruction, and appearance recovery;and as controlled imagery for integration into existing GIS systems and applications. The web-based interface to the data provides interactive viewing of high-dynamic-range images and mosaics;extracted edge and point features;intrinsic and extrinsic calibration, along with maps of the ground context in which the images were acquired;the spatial adjacency relationships among images;the epipolar geometry relating adjacent images;, compass and absolute scale overlays;and quantitative consistency measures for the calibration data.
In this work we demonstrate that a recently introduced shape descriptor, the "shape context", can be used to quickly prune a search for similar shapes. Our representation for a shape is a discrete set of n p...
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ISBN:
(纸本)0769512720
In this work we demonstrate that a recently introduced shape descriptor, the "shape context", can be used to quickly prune a search for similar shapes. Our representation for a shape is a discrete set of n points sampled from its internal and external contours. For each of these points, the shape context is a histogram of the relative positions of the n - 1 remaining points. We present two methods for rapid shape retrieval: one that does comparisons based on a small number of shape contexts and another that uses vector quantization in the space of shape contexts. We verify the discriminative power of these methods with tests on the Columbia (COIL-100) 3D object database and the Snod-grass and Vanderwart line drawings. The shape context-based methods are shown to quickly produce an accurate shortlist of candidates suitable for a more exact matching engine in spite of pose variation and occlusion.
Grouping by graph partitioning is an effective engine for perceptual organization. This graph partitioning process, mainly motivated by computational efficiency considerations, is usually implemented as recursive bi-p...
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ISBN:
(纸本)0769512720
Grouping by graph partitioning is an effective engine for perceptual organization. This graph partitioning process, mainly motivated by computational efficiency considerations, is usually implemented as recursive bi-partitioning, where at each step the graph is broken into two parts based on a partitioning measure. We study four such measures, namely, the minimum cut [11], average cut [6], Shi-Malik normalized cut [7], and a variation of the Shi-Malik normalized cut. Using probabilistic analysis we show that the minimization of the average cut and the normalized cut measure, using recursive bi-partitioning will, on an average, result in the correct segmentation. The minimum cut and the variation of the normalized cut will, on an average, not result in the correct segmentation and we can precisely express the conditions. Based on a rigorous empirical evaluation, we also show that, in practice, the quality of the groups generated using minimum, average or normalized cuts are statistically equivalent for object recognition, i.e. the best, the mean, and the variation of the qualities are statistically equivalent. We also find that for certain image classes, such as aerial and scenes with man-made objects in man-made surroundings, the performance of grouping by partitioning is the worst, irrespective of the cut measure.
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