58 research outputs found
Face Captioning Using Prominent Feature Recognition
Humans rely on prominent feature recognition to correctly identify and describe previously seen faces. Despite this fact, there is little existing work investigating how prominent facial features can be automatically recognized and used to create natural language face descriptions. Facial attribute prediction, a more commonly studied problem in computer vision, has previously been used for this task. However, the evaluation metrics and baseline models currently used to compare different attribute prediction methods are insufficient for determining which approaches are best at classifying highly imbalanced attributes. We also show that CelebA, the largest and most widely used facial attribute dataset, is too poorly labeled to be suitable for prominent feature recognition. To deal with these issues, we propose a method for generating weak prominent feature labels using semantic segmentation and show that we can use these labels to improve attribute-based face description
Feature regularization and learning for human activity recognition.
Doctoral Degree. University of KwaZulu-Natal, Durban.Feature extraction is an essential component in the design of human activity
recognition model. However, relying on extracted features alone for learning often makes the model a suboptimal model. Therefore, this research
work seeks to address such potential problem by investigating feature regularization. Feature regularization is used for encapsulating discriminative
patterns that are needed for better and efficient model learning. Firstly, a
within-class subspace regularization approach is proposed for eigenfeatures
extraction and regularization in human activity recognition. In this ap-
proach, the within-class subspace is modelled using more eigenvalues from
the reliable subspace to obtain a four-parameter modelling scheme. This
model enables a better and true estimation of the eigenvalues that are distorted by the small sample size effect. This regularization is done in one
piece, thereby avoiding undue complexity of modelling eigenspectrum differently. The whole eigenspace is used for performance evaluation because
feature extraction and dimensionality reduction are done at a later stage
of the evaluation process. Results show that the proposed approach has
better discriminative capacity than several other subspace approaches for
human activity recognition. Secondly, with the use of likelihood prior probability, a new regularization scheme that improves the loss function of deep
convolutional neural network is proposed. The results obtained from this
work demonstrate that a well regularized feature yields better class discrimination in human activity recognition. The major contribution of the
thesis is the development of feature extraction strategies for determining
discriminative patterns needed for efficient model learning
Impact and Detection of Facial Beautification in Face Recognition: An Overview
International audienceFacial beautification induced by plastic surgery, cosmetics or retouching has the ability to substantially alter the appearance of face images. Such types of beautification can negatively affect the accuracy of face recognition systems. In this work, a conceptual categorisation of beautification is presented, relevant scenarios with respect to face recognition are discussed, and related publications are revisited. Additionally, technical considerations and trade-offs of the surveyed methods are summarized along with open issues and challenges in the field. This survey is targeted to provide a comprehensive point of reference for biometric researchers and practitioners working in the field of face recognition, who aim at tackling challenges caused by facial beautification
Hierarchical age estimation using enhanced facial features.
Doctor of Philosopy in Computer Science, University of KwaZulu-Natal, Westville, 2018.Ageing is a stochastic, inevitable and uncontrollable process that constantly affect
shape, texture and general appearance of the human face. Humans can easily determine
ones’ gender, identity and ethnicity with highest accuracy as compared to
age. This makes development of automatic age estimation techniques that surpass
human performance an attractive yet challenging task. Automatic age estimation
requires extraction of robust and reliable age discriminative features. Local binary
patterns (LBP) sensitivity to noise makes it insufficiently reliable in capturing age
discriminative features. Although local ternary patterns (LTP) is insensitive to noise,
it uses a single static threshold for all images regardless of varied image conditions.
Local directional patterns (LDP) uses k directional responses to encode image gradient
and disregards not only central pixel in the local neighborhood but also 8 k
directional responses. Every pixel in an image carry subtle information. Discarding
8 k directional responses lead to lose of discriminative texture features. This
study proposes two variations of LDP operator for texture extraction. Significantorientation
response LDP (SOR-LDP) encodes image gradient by grouping eight
directional responses into four pairs. Each pair represents orientation of an edge
with respect to central reference pixel. Values in each pair are compared and the
bit corresponding to the maximum value in the pair is set to 1 while the other is
set to 0. The resultant binary code is converted to decimal and assigned to the central
pixel as its’ SOR-LDP code. Texture features are contained in the histogram of
SOR-LDP encoded image. Local ternary directional patterns (LTDP) first gets the
difference between neighboring pixels and central pixel in 3 3 image region. These
differential values are convolved with Kirsch edge detectors to obtain directional
responses. These responses are normalized and used as probability of an edge occurring
towards a respective direction. An adaptive threshold is applied to derive
LTDP code. The LTDP code is split into its positive and negative LTDP codes. Histograms
of negative and positive LTDP encoded images are concatenated to obtain
texture feature. Regardless of there being evidence of spatial frequency processing
in primary visual cortex, biologically inspired features (BIF) that model visual cortex
uses only scale and orientation selectivity in feature extraction. Furthermore,
these BIF are extracted using holistic (global) pooling across scale and orientations
leading to lose of substantive information. This study proposes multi-frequency BIF
(MF-BIF) where frequency selectivity is introduced in BIF modelling. Local statistical
BIF (LS-BIF) uses local pooling within scale, orientation and frequency in n n
region for BIF extraction. Using Leave-one-person-out (LOPO) validation protocol,
this study investigated performance of proposed feature extractors in age estimation
in a hierarchical way by performing age-group classification using Multi-layer
Perceptron (MLP) followed by within age-group exact age regression using support
vector regression (SVR). Mean absolute error (MAE) and cumulative score (CS) were
used to evaluate performance of proposed face descriptors. Experimental results on
FG-NET ageing dataset show that SOR-LDP, LTDP, MF-BIF and LS-BIF outperform
state-of-the-art feature descriptors in age estimation. Experimental results show that
performing gender discrimination before age-group and age estimation further improves
age estimation accuracies. Shape, appearance, wrinkle and texture features
are simultaneously extracted by visual system in primates for the brain to process
and understand an image or a scene. However, age estimation systems in the literature
use a single feature for age estimation. A single feature is not sufficient enough
to capture subtle age discriminative traits due to stochastic and personalized nature
of ageing. This study propose fusion of different facial features to enhance their
discriminative power. Experimental results show that fusing shape, texture, wrinkle
and appearance result into robust age discriminative features that achieve lower
MAE compared to single feature performance
Object Recognition
Vision-based object recognition tasks are very familiar in our everyday activities, such as driving our car in the correct lane. We do these tasks effortlessly in real-time. In the last decades, with the advancement of computer technology, researchers and application developers are trying to mimic the human's capability of visually recognising. Such capability will allow machine to free human from boring or dangerous jobs
IDENTITY CRISIS: WHEN FACE RECOGNITION MEETS TWINS AND PRIVACY
Ph.DDOCTOR OF PHILOSOPH
- …