183 research outputs found
FACE RECOGNITION AND VERIFICATION IN UNCONSTRAINED ENVIRIONMENTS
Face recognition has been a long standing problem in computer vision. General
face recognition is challenging because of large appearance variability due to
factors including pose, ambient lighting, expression, size of the face, age, and distance
from the camera, etc. There are very accurate techniques to perform face
recognition in controlled environments, especially when large numbers of samples
are available for each face (individual). However, face identification under uncontrolled(
unconstrained) environments or with limited training data is still an unsolved
problem. There are two face recognition tasks: face identification (who is who in
a probe face set, given a gallery face set) and face verification (same or not, given
two faces). In this work, we study both face identification and verification in unconstrained
environments.
Firstly, we propose a face verification framework that combines Partial Least
Squares (PLS) and the One-Shot similarity model[1]. The idea is to describe a
face with a large feature set combining shape, texture and color information. PLS
regression is applied to perform multi-channel feature weighting on this large feature
set. Finally the PLS regression is used to compute the similarity score of an image
pair by One-Shot learning (using a fixed negative set).
Secondly, we study face identification with image sets, where the gallery and
probe are sets of face images of an individual. We model a face set by its covariance
matrix (COV) which is a natural 2nd-order statistic of a sample set.By exploring an
efficient metric for the SPD matrices, i.e., Log-Euclidean Distance (LED), we derive
a kernel function that explicitly maps the covariance matrix from the Riemannian
manifold to Euclidean space. Then, discriminative learning is performed on the
COV manifold: the learning aims to maximize the between-class COV distance and
minimize the within-class COV distance.
Sparse representation and dictionary learning have been widely used in face
recognition, especially when large numbers of samples are available for each face
(individual). Sparse coding is promising since it provides a more stable and discriminative
face representation. In the last part of our work, we explore sparse
coding and dictionary learning for face verification application. More specifically,
in one approach, we apply sparse representations to face verification in two ways
via a fix reference set as dictionary. In the other approach, we propose a dictionary
learning framework with explicit pairwise constraints, which unifies the discriminative
dictionary learning for pair matching (face verification) and classification (face
recognition) problems
Deep Adaptive Feature Embedding with Local Sample Distributions for Person Re-identification
Person re-identification (re-id) aims to match pedestrians observed by
disjoint camera views. It attracts increasing attention in computer vision due
to its importance to surveillance system. To combat the major challenge of
cross-view visual variations, deep embedding approaches are proposed by
learning a compact feature space from images such that the Euclidean distances
correspond to their cross-view similarity metric. However, the global Euclidean
distance cannot faithfully characterize the ideal similarity in a complex
visual feature space because features of pedestrian images exhibit unknown
distributions due to large variations in poses, illumination and occlusion.
Moreover, intra-personal training samples within a local range are robust to
guide deep embedding against uncontrolled variations, which however, cannot be
captured by a global Euclidean distance. In this paper, we study the problem of
person re-id by proposing a novel sampling to mine suitable \textit{positives}
(i.e. intra-class) within a local range to improve the deep embedding in the
context of large intra-class variations. Our method is capable of learning a
deep similarity metric adaptive to local sample structure by minimizing each
sample's local distances while propagating through the relationship between
samples to attain the whole intra-class minimization. To this end, a novel
objective function is proposed to jointly optimize similarity metric learning,
local positive mining and robust deep embedding. This yields local
discriminations by selecting local-ranged positive samples, and the learned
features are robust to dramatic intra-class variations. Experiments on
benchmarks show state-of-the-art results achieved by our method.Comment: Published on Pattern Recognitio
Hyperbolic Deep Neural Networks: A Survey
Recently, there has been a rising surge of momentum for deep representation
learning in hyperbolic spaces due to theirhigh capacity of modeling data like
knowledge graphs or synonym hierarchies, possessing hierarchical structure. We
refer to the model as hyperbolic deep neural network in this paper. Such a
hyperbolic neural architecture potentially leads to drastically compact model
withmuch more physical interpretability than its counterpart in Euclidean
space. To stimulate future research, this paper presents acoherent and
comprehensive review of the literature around the neural components in the
construction of hyperbolic deep neuralnetworks, as well as the generalization
of the leading deep approaches to the Hyperbolic space. It also presents
current applicationsaround various machine learning tasks on several publicly
available datasets, together with insightful observations and identifying
openquestions and promising future directions
HIER: Metric Learning Beyond Class Labels via Hierarchical Regularization
Supervision for metric learning has long been given in the form of
equivalence between human-labeled classes. Although this type of supervision
has been a basis of metric learning for decades, we argue that it hinders
further advances of the field. In this regard, we propose a new regularization
method, dubbed HIER, to discover the latent semantic hierarchy of training
data, and to deploy the hierarchy to provide richer and more fine-grained
supervision than inter-class separability induced by common metric learning
losses. HIER achieved this goal with no annotation for the semantic hierarchy
but by learning hierarchical proxies in hyperbolic spaces. The hierarchical
proxies are learnable parameters, and each of them is trained to serve as an
ancestor of a group of data or other proxies to approximate the semantic
hierarchy among them. HIER deals with the proxies along with data in hyperbolic
space since geometric properties of the space are well-suited to represent
their hierarchical structure. The efficacy of HIER was evaluated on four
standard benchmarks, where it consistently improved performance of conventional
methods when integrated with them, and consequently achieved the best records,
surpassing even the existing hyperbolic metric learning technique, in almost
all settings
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