3,254 research outputs found
Efficiently Tracking Homogeneous Regions in Multichannel Images
We present a method for tracking Maximally Stable Homogeneous Regions (MSHR)
in images with an arbitrary number of channels. MSHR are conceptionally very
similar to Maximally Stable Extremal Regions (MSER) and Maximally Stable Color
Regions (MSCR), but can also be applied to hyperspectral and color images while
remaining extremely efficient. The presented approach makes use of the
edge-based component-tree which can be calculated in linear time. In the
tracking step, the MSHR are localized by matching them to the nodes in the
component-tree. We use rotationally invariant region and gray-value features
that can be calculated through first and second order moments at low
computational complexity. Furthermore, we use a weighted feature vector to
improve the data association in the tracking step. The algorithm is evaluated
on a collection of different tracking scenes from the literature. Furthermore,
we present two different applications: 2D object tracking and the 3D
segmentation of organs.Comment: to be published in ICPRS 2017 proceeding
A robust nonlinear scale space change detection approach for SAR images
In this paper, we propose a change detection approach based on nonlinear scale space analysis of change images for robust detection of various changes incurred by natural phenomena and/or human activities in Synthetic Aperture Radar (SAR) images using Maximally Stable Extremal Regions (MSERs). To achieve this, a variant of the log-ratio image of multitemporal images is calculated which is followed by Feature Preserving Despeckling (FPD) to generate nonlinear scale space images exhibiting different trade-offs in terms of speckle reduction and shape detail preservation. MSERs of each scale space image are found and then combined through a decision level fusion strategy, namely "selective scale fusion" (SSF), where contrast and boundary curvature of each MSER are considered. The performance of the proposed method is evaluated using real multitemporal high resolution TerraSAR-X images and synthetically generated multitemporal images composed of shapes with several orientations, sizes, and backscatter amplitude levels representing a variety of possible signatures of change. One of the main outcomes of this approach is that different objects having different sizes and levels of contrast with their surroundings appear as stable regions at different scale space images thus the fusion of results from scale space images yields a good overall performance
A Lovelock black hole bestiary
We revisit the study of (A)dS black holes in Lovelock theories. We present a
new tool that allows to attack this problem in full generality. In analyzing
maximally symmetric Lovelock black holes with non-planar horizon topologies
many distinctive and interesting features are observed. Among them, the
existence of maximally symmetric vacua do not supporting black holes in vast
regions of the space of gravitational couplings, multi-horizon black holes, and
branches of solutions that suggest the existence of a rich diagram of phase
transitions. The appearance of naked singularities seems unavoidable in some
cases, raising the question about the fate of the cosmic censorship conjecture
in these theories. There is a preferred branch of solutions for planar black
holes, as well as non-planar black holes with high enough mass or temperature.
Our study clarifies the role of all branches of solutions, including
asymptotically dS black holes, and whether they should be considered when
studying these theories in the context of AdS/CFT.Comment: 40 pages, 16 figures; v2: references added and minor amendments; v3:
title changed to improve its accuracy and general reorganization of the
results to ameliorate their presentatio
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