A spatiotemporal (ST) image cube, created by stacking a temporally dense sequence of images together, is a temporally coherent data representation. Using ST surface flow, i.e., the extension of optical flow to ST surf...
详细信息
ISBN:
(纸本)0818621486
A spatiotemporal (ST) image cube, created by stacking a temporally dense sequence of images together, is a temporally coherent data representation. Using ST surface flow, i.e., the extension of optical flow to ST surfaces, it is shown how ST flow curves can be recovered and then used to detect groups of flow curves such that each group represents a single object or surface in the scene undergoing motion. The algorithm forms clusters of similar flow curves and is based on constraints called the temporal uniqueness constraints. First, a point in an image can only move to at most one point in the next image. Second, a point in an image can come from at most one point in the previous image. When these constraints are violated, or it appears that they are violated, occlusion or disocclusion has occurred and therefore can also be detected. Successful grouping of coherent regions of the ST cube for two gray-level image sequences is shown.
A 3-D deformable model is introduced which evolves in true 3-D images, under the action of internal forces (describing some elasticity properties of the surface), and external forces attracting the surface toward some...
详细信息
ISBN:
(纸本)0818621486
A 3-D deformable model is introduced which evolves in true 3-D images, under the action of internal forces (describing some elasticity properties of the surface), and external forces attracting the surface toward some detected edgels. The formalism leads to the minimization of an energy which is expressed as a functional. The authors use a variational approach and a finite-element method to express the surface in a discrete basis of continuous functions. This leads to a reduced computational complexity and a better numerical stability. The power of the approach to segment 3-D images is demonstrated by a set of experimental results on various complex medical 3-D images.
The major direct solutions to the three-point perspective pose estimation problems are reviewed from a unified perspective. The numerical stability of these three-point perspective solutions are discussed. It is shown...
详细信息
ISBN:
(纸本)0818621486
The major direct solutions to the three-point perspective pose estimation problems are reviewed from a unified perspective. The numerical stability of these three-point perspective solutions are discussed. It is shown that even in cases where the solution is not near the geometric unstable region considerable care must be exercised in the calculation. Depending on the order of the substitutions utilized, the relative error can change over a thousand to one. This difference is due entirely to the way the calculations are performed and not to any geometric structural instability of any problem instance. An analytical method is presented which produces a numerically stable calculation.
An optimal deformable contour approximation algorithm using a cardinal-form piecewise cubic spline (PCS) curve representation is presented. The approximation is optimal in the sense of least square errors in both loca...
详细信息
ISBN:
(纸本)0818621486
An optimal deformable contour approximation algorithm using a cardinal-form piecewise cubic spline (PCS) curve representation is presented. The approximation is optimal in the sense of least square errors in both location and orientation. The knots are set automatically at high curvature positions. The sample data are generated by a robust edge fragment detection algorithm which is optimal in the sense of a weighted absolute error. An initial contour placement algorithm uses a penalized maximum likelihood algorithm to group the edge fragments together for an initial contour. A controlled deformable contour algorithm refines the initial contour to cover meaningful edge features.
A noniterative approach to determine displacement vector fields with discontinuities is described. In order to overcome the limitations of current methods, the problem is regarded as a general modeling problem. From t...
详细信息
ISBN:
(纸本)0818621486
A noniterative approach to determine displacement vector fields with discontinuities is described. In order to overcome the limitations of current methods, the problem is regarded as a general modeling problem. From this point of view the imaging field consists of a set of regions with common properties and their boundaries. The strategy proposed is an analysis of consistency of the displacement estimators between different levels of regularization. This gives local but noisy evidence of possible model boundaries at multiple scales. With the two constraints of continuous lines of discontinuities and the spatial coincidence assumption, consistent boundary evidence is found. Based on this combined evidence the model is updated so that it describes homogeneous regions with sharp discontinuities.
A unified theoretical framework for motion transparency and motion boundaries by devising fundamental constraint equations of multiple optical flow is proposed. This framework can handle flow discontinuities at motion...
详细信息
ISBN:
(纸本)0818621486
A unified theoretical framework for motion transparency and motion boundaries by devising fundamental constraint equations of multiple optical flow is proposed. This framework can handle flow discontinuities at motion boundaries as well as flow multiplicities due to transparency of objects in a unified manner. The constraint equations are formulated by a composition of homogeneously parametrized differential operators on the space-time image. Fitting algorithms for the constraints which result in eigensystem analyses are described. To determine the number of flows, the authors use the margin energy, a measure of goodness of fit which is the difference between the first and the second lower eigenenergy of the eigensystem. They also hypothesize a criterion for multiplicity. The measure and the criterion are derived from the analogy of quantum mechanics. It is demonstrated that the margin energy can determine the transparency and discontinuities of the flow field as regions of more than one flow.
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...
详细信息
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 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 ...
详细信息
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.
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...
详细信息
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.
An algorithm that identifies inter-reflection by using chromatic information in color images is presented. Several experimental results from test images show that the proposed method could play the role of an added en...
详细信息
ISBN:
(纸本)0818621486
An algorithm that identifies inter-reflection by using chromatic information in color images is presented. Several experimental results from test images show that the proposed method could play the role of an added enhancement stage in the segmentation method using the dichromatic reflection model, and could be an independent identification scheme by itself. The algorithm does not consider multiple bounces of light and deals with body-to-body interreflection only. This model must be combined with other intrinsic models of surface properties such as metals which exhibit strong surface reflection but not body reflection.
暂无评论