The paper presents a novel processing.scheme for the automatic computation of a medial shape model which is representative for an object population with shape variability. The sensitivity of medial descriptions to obj...
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ISBN:
(纸本)0769512720
The paper presents a novel processing.scheme for the automatic computation of a medial shape model which is representative for an object population with shape variability. The sensitivity of medial descriptions to object variations and small boundary perturbations are fundamental problems of any skeletonization technique. These problems are approached with the computation of a model with common medial branching topology and grid sampling. This model is then used for a medial shape description of individual objects via a constrained model fit. The process starts from parametric 3D boundary representations with existing point-to-point homology between objects. The Voronoi diagram of each sampled object boundary is grouped into medial sheets and simplified by a pruning algorithm using a volumetric contribution criterion. Medial sheets are combined to form a common medial branching topology. Finally, the medial sheets are sampled and represented as meshes of medial primitives. We present new results on populations of up to 184 biological objects. For these objects, the common medial branching topology is described by a small number of sheets. Despite the coarse medial sampling, a close approximation of individual objects is achieved.
A problem in uncalibrated stereo reconstruction is that cameras which deviate from the pinhole model have to be pre-calibrated in order to correct for nonlinear lens distortion. If they are not, and point corresponden...
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ISBN:
(纸本)0769512720
A problem in uncalibrated stereo reconstruction is that cameras which deviate from the pinhole model have to be pre-calibrated in order to correct for nonlinear lens distortion. If they are not, and point correspondence is attempted using the uncorrected images, the matching constraints provided by the fundamental matrix must be set so loose that point matching is significantly hampered. This paper shows how linear estimation of the fundamental matrix from two-view point correspondences may be augmented to include one term of radial lens distortion. This is achieved by (1) changing from the standard radial-lens model to another which (as we show) has equivalent power, but which takes a simpler form in homogeneous coordinates, and (2) expressing fundamental matrix estimation as a quadratic eigenvalue problem (QEP), for which efficient algorithms are well known. I derive the new estimator, and compare its performance against bundle-adjusted calibration-grid data. The new estimator is fast enough to be included in a RANSAC-based matching loop, and we show cases of matching being rendered possible by its use. I show how the same lens can be calibrated in a natural scene where the lack of straight lines precludes most previous techniques. The modification when the multi-view relation is a planar homography or trifocal tensor is described.
We propose blind segmentation of images into shape-related 'patches' based on pre-calculated local symmetries (Van Tender, G.J. & Ejima, Y. (1999). (Forthcoming a) Flexible computation of shape symmetries....
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We propose blind segmentation of images into shape-related 'patches' based on pre-calculated local symmetries (Van Tender, G.J. & Ejima, Y. (1999). (Forthcoming a) Flexible computation of shape symmetries. Submitted for publication) in shape boundary contours. First, lateral weights between all points in the boundary contour map are assigned analogous to Euclidean distance maps in watershed segmentation (Beucher, S. & Lantejoul, C. (1979). Use of watersheds in contour detection. proceedings of the International Workshop on imageprocessing. CCETT, Rennes, France.). Lateral weights are then used to: (1) extract local maxima in symmetries;(2) link maxima within locally enclosed boundary contours;and (3) reconstruct shape contours using symmetry maxima as 'seeds'. The new model overcomes weaknesses of watershed segmentation. The new model closes gaps in relatively more solid image contours, but it is fundamentally different from methods based on contour interpolation (Grossberg, S., Mingolla, E. & Todorove, D. (1989). A neural network architecture for preattentive vision, ieee Transactions on Biomedical Engineering 36, 65-84;Heitger, F. & von der Heydt, R. (1993). A computational model of neural contour processing. figure-ground segregation and illusory contours. proceedings of the Fourth International conference on computer Vision, ieeecomputersociety Press, Washington D.C. (pp. 32-40)). images are segmented into shape-relevant color-by-number-like patches which compare well to related methods (Gauch, J. & Pizer, M. (1993). The intensity axis of symmetry and its application to image segmentation, ieee Transactions on pattern Analysis and Machine Intelligence, 15 (8), 753-770;Ilg, W. & Ogniewicz, R. (1995). The application of Voronoi skeletons to perceptual grouping in line images, proceedings of the 11th International conference on patternrecognition, The Hague, The Netherlands, pp. 382-385;Zhu, S.C. & Yuille, A.L. (1996) FORMS: a flexible object recognition and mo
In this paper, we developed a color model to cancel the dependency between color channels, which enables us to separate spectral processing.from spatial processing. We introduced Independent Component Analysis (ICA) t...
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In this paper, we developed a color model to cancel the dependency between color channels, which enables us to separate spectral processing.from spatial processing. We introduced Independent Component Analysis (ICA) transformation in the wavelet domain to decorrelate the subband color joint statistics. The decorrelated joint color conditional histograms display scaling of variance. Gaussian Scale Mixture (GSM) was used to model the subband color statistics and a normalization scheme was adapted to cancel the pair-wise color subband statistical dependency. This color model was combined with the Portilla/Simoncelli texture model to construct the color texture model. Based on this model, features were extracted and the corresponding color texture synthesis scheme was developed.
The measurement of object reflectance from color images is carried out. Illumination and geometrical invariant properties are derived from a physical reflectance model based on the Kubelka-Munk theory. Invariance, dis...
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The measurement of object reflectance from color images is carried out. Illumination and geometrical invariant properties are derived from a physical reflectance model based on the Kubelka-Munk theory. Invariance, discriminative power and localization accuracy of the color invariants are extensively studied. Experiments show the different invariants to be highly discriminative while maintaining invariance properties.
In this paper, a novel scheme of extracting multiple illuminant directions from an image of a Lambertian sphere of known size is proposed. The illuminant direction detection process is based on the concept of critical...
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In this paper, a novel scheme of extracting multiple illuminant directions from an image of a Lambertian sphere of known size is proposed. The illuminant direction detection process is based on the concept of critical points introduced in the paper. We show that the illuminant directions have a close relationship to those critical points and that, by identifying those critical points as many as possible, illuminant directions may be recovered if certain conditions are satisfied. Our preliminary experimental results show that illumination information can be obtained accurately.
We will demonstrate our CVPR2000 paper 'Measurement of Color Invariants' for the cases of image retrieval based on query by example and for color image segmentation. Both are of importance in content based acc...
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We will demonstrate our CVPR2000 paper 'Measurement of Color Invariants' for the cases of image retrieval based on query by example and for color image segmentation. Both are of importance in content based access of image and video data. We demonstrate the usefulness of the proposed color invariants in image retrieval by example systems. We show that an image retrieval query should include the type of invariance expected in the result. We demonstrate such queries by using the 'imageSurf' retrieval system. Segmentation of images based on the proposed color invariants is demonstrated by the 'PicToVision' system. The system provides imageprocessing.functionality through the world wide web, and is publicly accessible at ***/research/isis/***.
We present two families of reflective surfaces that are capable of providing a wide field of view, and yet still approximate a perspective projection to a high degree. These surfaces are derived by considering a plane...
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ISBN:
(纸本)0769507042;0769507050
We present two families of reflective surfaces that are capable of providing a wide field of view, and yet still approximate a perspective projection to a high degree. These surfaces are derived by considering a plane perpendicular to the axis of a surface of revolution and finding the equations governing the distortion of the image of the plane in this surface. We then view this relation as a differential equation and prescribe the distortion term to be linear. By choosing appropriate initial conditions for the differential equation and solving it numerically, we derive the surface shape and obtain a precise estimate as to what degree the resulting sensor can approximate a perspective projection. Thus these surfaces act as computational sensors, allowing for a wide-angle perspective view of a scene without processing.the image in software. The applications of such a sensor should be numerous, including surveillance, robotics and traditional photography.
The design of an effective architecture for content-based retrieval from visual libraries requires careful consideration of the interplay between feature selection, feature representation, and similarity metric. We pr...
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The design of an effective architecture for content-based retrieval from visual libraries requires careful consideration of the interplay between feature selection, feature representation, and similarity metric. We present a solution where all the modules strive to optimize the same performance criteria: the probability of retrieval error. This solution consists of a Bayesian retrieval criteria (shown to generalize the most prevalent similarity metrics in current use) and an embedded mixture representation over a multiresolution feature space (shown to provide a good trade-off between retrieval accuracy, invariance, perceptual relevance of similarity judgments, and complexity). The new representation extends standard models (histogram and Gaussian) by providing simultaneous support for high-dimensional features and multi-modal densities and performs well on color, texture, and generic image databases.
This paper examines the problem of image retrieval from large, heterogeneous image databases. We present a technique that fulfills several needs identified by surveying recent research in the field. This technique fai...
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This paper examines the problem of image retrieval from large, heterogeneous image databases. We present a technique that fulfills several needs identified by surveying recent research in the field. This technique fairly integrates a diverse and expandable set of image properties (for example, color, texture, and location) in a retrieval framework, and allows end-users substantial control over their use. We propose a novel set of evaluation methods in addition to applying established tests for image retrieval;our technique proves competitive with state-of-the-art methods in these tests and does better on certain tasks. Furthermore, it improves on many standard image retrieval algorithms by supporting queries based on subsections of images. For certain queries this capability significantly increases the relevance of the images retrieved, and further expands the user's control over the retrieval process.
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