An approach for determining the location and orientation of a camera mounted on an ALV (autonomous land vehicle) is proposed. The authors choose the road boundaries and the objects with vertical edges to be the calibr...
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ISBN:
(纸本)0818621486
An approach for determining the location and orientation of a camera mounted on an ALV (autonomous land vehicle) is proposed. The authors choose the road boundaries and the objects with vertical edges to be the calibration objects. During the calibration process, the ALV is supposed to move with pure translation. The camera models are derived by using two or three images under the assumptions that the height of the camera and the distance during taking images are known in advance. The tilt and swing angles can be computed from the first image. The pan angle can then be derived by using the projections of vertical edges in three images. If the angle between the moving direction of the ALV and the direction of road boundaries is large enough, two images are enough to find the pan angle. Two translational parameters can be found by employing the projections of vertical edges in two or three images.
An 'aura' framework is used to rewrite the nonlinear energy function of a homogeneous anisotropic Markov/Gibbs random field (MRF) as a linear sum of aura measures. The formulation relates MRFs to co-occurrence...
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ISBN:
(纸本)0818621486
An 'aura' framework is used to rewrite the nonlinear energy function of a homogeneous anisotropic Markov/Gibbs random field (MRF) as a linear sum of aura measures. The formulation relates MRFs to co-occurrence matrices. It also provides a physical interpretation of MRF textures in terms of the mixing and separation of gray-level sets, and in terms of boundary maximization and minimization. Within this framework, the authors introduce the use of temperature for texture modeling and show how the parameters of the MRF can be interpreted as temperature annealing rates. In particular, they show evidence for a transition temperature, above which all patterns generated will be visually similar, and below which a pattern evolves down to its ground state. Results which characterize the ground state patterns are described.
A method for recovering shape from shading that solves directly for the surface height is presented. By using a discrete formulation of the problem, it is possible to achieve good convergence behavior by employing num...
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ISBN:
(纸本)0818621486
A method for recovering shape from shading that solves directly for the surface height is presented. By using a discrete formulation of the problem, it is possible to achieve good convergence behavior by employing numerical solution techniques more powerful than gradient descent methods derived from variational calculus. Because this method solves directly for height, it avoids the problem of finding an integrable surface maximally consistent with surface orientation. Furthermore, since additional constraints are not needed to make the problem well posed, a smoothness constraint is used only to drive the system towards a good solution;the weight of the smoothness term is eventually reduced to near zero. By solving directly for height, stereo processing.may be used to provide initial and boundary conditions. The shape from shading technique, as well as its relation to stereo, is demonstrated on both synthetic and real imagery.
A direct method called fixation is introduced for solving the general motion vision problem, arbitrary motion relative to an arbitrary rigid scene. This method results in a linear constraint equation which explicitly ...
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ISBN:
(纸本)0818621486
A direct method called fixation is introduced for solving the general motion vision problem, arbitrary motion relative to an arbitrary rigid scene. This method results in a linear constraint equation which explicitly expresses rotational velocity in terms of translational velocity. By combining this constraint equation with the brightness-change constraint equation, general solutions are found for translational and rotational velocities, and the shape. Avoiding correspondence and optical flow has been the motivation behind this direct method, which uses the brightness gradients directly. Partial implementation of the fixation method on real images has shown encouraging results which support some of the presented algorithms.
An edge-based trinocular stereovision algorithm is presented. The primitives it works on are cubic B-spline approximations of the 2-D edges. This allows one to deal conveniently with curvature and to extend to some no...
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ISBN:
(纸本)0818621486
An edge-based trinocular stereovision algorithm is presented. The primitives it works on are cubic B-spline approximations of the 2-D edges. This allows one to deal conveniently with curvature and to extend to some non-polyhedral scenes to previous stereo algorithms. To build a matching primitive, the principle of the algorithm is, first, to find a triplet of corresponding points on three splines. This is provided by the bootstrapping part. Second, the algorithm propagates along the three supporting splines to find other matching points. This provides a set of ordered point triplets along these three splines, for which all the matching constraints are verified. This primitive constitutes a trinocular hypothesis. The set of all hypotheses is obtained by propagating from all the point triplets provided by the bootstrapping process. A criterion based on the size of the hypotheses is then used to choose among them a compatible set with respect to the uniqueness constraint. Results of several 3-D reconstructed scenes are shown.
The authors present region-based imageprocessing.algorithms participating in task sequencing for stereo vision. The algorithms described are prior to stereo matching. Requirements in image similarity provide helpful ...
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The authors present region-based imageprocessing.algorithms participating in task sequencing for stereo vision. The algorithms described are prior to stereo matching. Requirements in image similarity provide helpful additional knowledge for their improvement. A recursive region division algorithm using a threshold method based on contrast maximization is described. The regions are processed in parallel and absorb their noise before being thresholded. Subsequent morphological processes improve similarity and matching results. Additional knowledge is produced by analytical processes, and is useful for both segmentation and match control. Results are presented for a stereo pair of gray-level images.< >
A vectorization method for line patterns which converts digital binary images into line-segment vectors is proposed. The proposed method suppresses shape distortion as well as pseudo-feature points, so it produces mor...
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A vectorization method for line patterns which converts digital binary images into line-segment vectors is proposed. The proposed method suppresses shape distortion as well as pseudo-feature points, so it produces more compact and natural-shaped vector data than existing methods. The experimental results of applying the proposed method to geographical maps show that the vectorization method reduces data volume by 74%-87% and suppresses shape distortion more than is possible with a straightforward method.< >
A facial feature classification technique that independently captures both the geometric configuration and the image detail of a particular feature is described. The geometric configuration is first extracted by fitti...
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A facial feature classification technique that independently captures both the geometric configuration and the image detail of a particular feature is described. The geometric configuration is first extracted by fitting a deformable template to the shape of the feature (for example, an eye) in the image. This information is then used to geometrically normalize the image in such a way that the feature in the image attains a standard shape. The normalized image of the facial feature is then classified in terms of a set of principal components previously obtained from a representative set of training images of similar features. This classification stage yields a representation vector which can be used for recognition matching of the feature in terms of image detail alone without the complication of changes in facial expression. Implementation of the system is described and results are given for its application to a set of test faces. These results show that features can be reliably recognized using the representation vectors obtained.< >
An approach which allows an arbitrary structure estimation to be embedded into a recursive estimation process that incrementally improves a structure estimate with every new frame that becomes available is discussed. ...
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An approach which allows an arbitrary structure estimation to be embedded into a recursive estimation process that incrementally improves a structure estimate with every new frame that becomes available is discussed. The approach is based on Bayesian estimation theory and the Kalman filter. The authors demonstrate how it may be applied to such domains as depth from motion and depth from shading.< >
A unified approach to boundary perception is presented. The model consists of a hierarchical system which extracts and groups salient features in the image at different spatial scales. In the first stage a Gabor wavel...
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A unified approach to boundary perception is presented. The model consists of a hierarchical system which extracts and groups salient features in the image at different spatial scales. In the first stage a Gabor wavelet decomposition provides a representation of the image which is orientation selective, has optimal localization properties, and provides a good model for early feature detection. Following this, local competitive interactions are introduced which help in reducing the effects of noise and illumination variations. Scale interactions help in localizing line ends and corners, and play an important role in boundary perception. The final stage groups similar features aiding in boundary completion. Experimental results on detecting edges, texture boundaries, and illusory contours are provided.< >
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