Showing papers by "Peter Meer published in 2002"

Mean shift: a robust approach toward feature space analysis

Abstract: A general non-parametric technique is proposed for the analysis of a complex multimodal feature space and to delineate arbitrarily shaped clusters in it. The basic computational module of the technique is an old pattern recognition procedure: the mean shift. For discrete data, we prove the convergence of a recursive mean shift procedure to the nearest stationary point of the underlying density function and, thus, its utility in detecting the modes of the density. The relation of the mean shift procedure to the Nadaraya-Watson estimator from kernel regression and the robust M-estimators; of location is also established. Algorithms for two low-level vision tasks discontinuity-preserving smoothing and image segmentation - are described as applications. In these algorithms, the only user-set parameter is the resolution of the analysis, and either gray-level or color images are accepted as input. Extensive experimental results illustrate their excellent performance.

Synergism in low level vision

Abstract: Guiding image segmentation with edge information is an often employed strategy in low level computer vision. To improve the trade-off between the sensitivity of homogeneous region delineation and the over-segmentation on of the image, we have incorporated a recently proposed edge magnitude/confidence map into a color image segmenter based on the mean shift procedure. The new method can recover regions with weak but sharp boundaries and thus can provide a more accurate input for high level interpretation modules. The edge detection and image segmentation (EDISON) system, available for download, implements the proposed technique and provides a complete toolbox for discontinuity preserving filtering, segmentation and edge detection.

Robust Computer Vision through Kernel Density Estimation

Abstract: Two new techniques based on nonparametric estimation of probability densities are introduced which improve on the performance of equivalent robust methods currently employed in computer vision. The first technique draws from the projection pursuit paradigm in statistics, and carries out regression M-estimation with a weak dependence on the accuracy of the scale estimate. The second technique exploits the properties of the multivariate adaptive mean shift, and accomplishes the fusion of uncertain measurements arising from an unknown number of sources. As an example, the two techniques are extensively used in an algorithm for the recovery of multiple structures from heavily corrupted data.

Balanced Recovery of 3D Structure and Camera Motion from Uncalibrated Image Sequences

Abstract: Metric reconstruction of a scene viewed by an uncalibrated camera undergoing an unknown motion is a fundamental task in computer vision. To obtain accurate results all the methods rely on bundle adjustment, a nonlinear optimization technique which minimizes the reprojection error over the structural and camera parameters. Bundle adjustment is optimal for normally distributed measurement noise, however, its performance depends on the starting point. The initial solution is usually obtained by solving a linearized constraint through a total least squares procedure, which yields a biased estimate. We present a more balanced approach where in main computational modules of an uncalibrated reconstruction system, the initial solution is obtained from a statistically justified estimator which assures its unbiasedness. Since the quality of the new initial solution is already comparable with that of the result of bundle adjustment, the burden on the latter is drastically reduced while its reliability is significantly increased. The performance of our system was assessed for both synthetic data and standard image sequences.