13,599 research outputs found
Guided Curriculum Model Adaptation and Uncertainty-Aware Evaluation for Semantic Nighttime Image Segmentation
Most progress in semantic segmentation reports on daytime images taken under
favorable illumination conditions. We instead address the problem of semantic
segmentation of nighttime images and improve the state-of-the-art, by adapting
daytime models to nighttime without using nighttime annotations. Moreover, we
design a new evaluation framework to address the substantial uncertainty of
semantics in nighttime images. Our central contributions are: 1) a curriculum
framework to gradually adapt semantic segmentation models from day to night via
labeled synthetic images and unlabeled real images, both for progressively
darker times of day, which exploits cross-time-of-day correspondences for the
real images to guide the inference of their labels; 2) a novel
uncertainty-aware annotation and evaluation framework and metric for semantic
segmentation, designed for adverse conditions and including image regions
beyond human recognition capability in the evaluation in a principled fashion;
3) the Dark Zurich dataset, which comprises 2416 unlabeled nighttime and 2920
unlabeled twilight images with correspondences to their daytime counterparts
plus a set of 151 nighttime images with fine pixel-level annotations created
with our protocol, which serves as a first benchmark to perform our novel
evaluation. Experiments show that our guided curriculum adaptation
significantly outperforms state-of-the-art methods on real nighttime sets both
for standard metrics and our uncertainty-aware metric. Furthermore, our
uncertainty-aware evaluation reveals that selective invalidation of predictions
can lead to better results on data with ambiguous content such as our nighttime
benchmark and profit safety-oriented applications which involve invalid inputs.Comment: ICCV 2019 camera-read
Map-Guided Curriculum Domain Adaptation and Uncertainty-Aware Evaluation for Semantic Nighttime Image Segmentation
We address the problem of semantic nighttime image segmentation and improve
the state-of-the-art, by adapting daytime models to nighttime without using
nighttime annotations. Moreover, we design a new evaluation framework to
address the substantial uncertainty of semantics in nighttime images. Our
central contributions are: 1) a curriculum framework to gradually adapt
semantic segmentation models from day to night through progressively darker
times of day, exploiting cross-time-of-day correspondences between daytime
images from a reference map and dark images to guide the label inference in the
dark domains; 2) a novel uncertainty-aware annotation and evaluation framework
and metric for semantic segmentation, including image regions beyond human
recognition capability in the evaluation in a principled fashion; 3) the Dark
Zurich dataset, comprising 2416 unlabeled nighttime and 2920 unlabeled twilight
images with correspondences to their daytime counterparts plus a set of 201
nighttime images with fine pixel-level annotations created with our protocol,
which serves as a first benchmark for our novel evaluation. Experiments show
that our map-guided curriculum adaptation significantly outperforms
state-of-the-art methods on nighttime sets both for standard metrics and our
uncertainty-aware metric. Furthermore, our uncertainty-aware evaluation reveals
that selective invalidation of predictions can improve results on data with
ambiguous content such as our benchmark and profit safety-oriented applications
involving invalid inputs.Comment: IEEE T-PAMI 202
Counting with Focus for Free
This paper aims to count arbitrary objects in images. The leading counting
approaches start from point annotations per object from which they construct
density maps. Then, their training objective transforms input images to density
maps through deep convolutional networks. We posit that the point annotations
serve more supervision purposes than just constructing density maps. We
introduce ways to repurpose the points for free. First, we propose supervised
focus from segmentation, where points are converted into binary maps. The
binary maps are combined with a network branch and accompanying loss function
to focus on areas of interest. Second, we propose supervised focus from global
density, where the ratio of point annotations to image pixels is used in
another branch to regularize the overall density estimation. To assist both the
density estimation and the focus from segmentation, we also introduce an
improved kernel size estimator for the point annotations. Experiments on six
datasets show that all our contributions reduce the counting error, regardless
of the base network, resulting in state-of-the-art accuracy using only a single
network. Finally, we are the first to count on WIDER FACE, allowing us to show
the benefits of our approach in handling varying object scales and crowding
levels. Code is available at
https://github.com/shizenglin/Counting-with-Focus-for-FreeComment: ICCV, 201
Computerized Analysis of Magnetic Resonance Images to Study Cerebral Anatomy in Developing Neonates
The study of cerebral anatomy in developing neonates is of great importance for
the understanding of brain development during the early period of life. This
dissertation therefore focuses on three challenges in the modelling of cerebral
anatomy in neonates during brain development. The methods that have been
developed all use Magnetic Resonance Images (MRI) as source data.
To facilitate study of vascular development in the neonatal period, a set of image
analysis algorithms are developed to automatically extract and model cerebral
vessel trees. The whole process consists of cerebral vessel tracking from
automatically placed seed points, vessel tree generation, and vasculature
registration and matching. These algorithms have been tested on clinical Time-of-
Flight (TOF) MR angiographic datasets.
To facilitate study of the neonatal cortex a complete cerebral cortex segmentation
and reconstruction pipeline has been developed. Segmentation of the neonatal
cortex is not effectively done by existing algorithms designed for the adult brain
because the contrast between grey and white matter is reversed. This causes pixels
containing tissue mixtures to be incorrectly labelled by conventional methods. The
neonatal cortical segmentation method that has been developed is based on a novel
expectation-maximization (EM) method with explicit correction for mislabelled
partial volume voxels. Based on the resulting cortical segmentation, an implicit
surface evolution technique is adopted for the reconstruction of the cortex in
neonates. The performance of the method is investigated by performing a detailed
landmark study.
To facilitate study of cortical development, a cortical surface registration algorithm
for aligning the cortical surface is developed. The method first inflates extracted
cortical surfaces and then performs a non-rigid surface registration using free-form
deformations (FFDs) to remove residual alignment. Validation experiments using
data labelled by an expert observer demonstrate that the method can capture local
changes and follow the growth of specific sulcus
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