On Designing Tattoo Registration and Matching Approaches in the Visible and SWIR Bands

Face, iris and fingerprint based biometric systems are well explored areas of research. However, there are law enforcement and military applications where neither of the aforementioned modalities may be available to be exploited for human identification. In such applications, soft biometrics may be the only clue available that can be used for identification or verification purposes. Tattoo is an example of such a soft biometric trait. Unlike face-based biometric systems that used in both same-spectral and cross-spectral matching scenarios, tattoo-based human identification is still a not fully explored area of research. At this point in time there are no pre-processing, feature extraction and matching algorithms using tattoo images captured at multiple bands. This thesis is focused on exploring solutions on two main challenging problems. The first one is cross-spectral tattoo matching. The proposed algorithmic approach is using as an input raw Short-Wave Infrared (SWIR) band tattoo images and matches them successfully against their visible band counterparts. The SWIR tattoo images are captured at 1100 nm, 1200 nm, 1300 nm, 1400 nm and 1500 nm. After an empirical study where multiple photometric normalization techniques were used to pre-process the original multi-band tattoo images, only one was determined to significantly improve cross spectral tattoo matching performance. The second challenging problem was to develop a fully automatic visible-based tattoo image registration system based on SIFT descriptors and the RANSAC algorithm with a homography model. The proposed automated registration approach significantly improves the operational cost of a tattoo image identification system (using large scale tattoo image datasets), where the alignment of a pair of tattoo images by system operators needs to be performed manually. At the same time, tattoo matching accuracy is also improved (before vs. after automated alignment) by 45.87% for the NIST-Tatt-C database and 12.65% for the WVU-Tatt database

Enhanced contextual based deep learning model for niqab face detection

Human face detection is one of the most investigated areas in computer vision which plays a fundamental role as the first step for all face processing and facial analysis systems, such as face recognition, security monitoring, and facial emotion recognition. Despite the great impact of Deep Learning Convolutional neural network (DL-CNN) approaches on solving many unconstrained face detection problems in recent years, the low performance of current face detection models when detecting highly occluded faces remains a challenging problem and worth of investigation. This challenge tends to be higher when the occlusion covers most of the face which dramatically reduce the number of learned representative features that are used by Feature Extraction Network (FEN) to discriminate face parts from the background. The lack of occluded face dataset with sufficient images for heavily occluded faces is another challenge that degrades the performance. Therefore, this research addressed the issue of low performance and developed an enhanced occluded face detection model for detecting and localizing heavily occluded faces. First, a highly occluded faces dataset was developed to provide sufficient training examples incorporated with contextual-based annotation technique, to maximize the amount of facial salient features. Second, using the training half of the dataset, a deep learning-CNN Occluded Face Detection model (OFD) with an enhanced feature extraction and detection network was proposed and trained. Common deep learning techniques, namely transfer learning and data augmentation techniques were used to speed up the training process. The false-positive reduction based on max-in-out strategy was adopted to reduce the high false-positive rate. The proposed model was evaluated and benchmarked with five current face detection models on the dataset. The obtained results show that OFD achieved improved performance in terms of accuracy (average 37%), and average precision (16.6%) compared to current face detection models. The findings revealed that the proposed model outperformed current face detection models in improving the detection of highly occluded faces. Based on the findings, an improved contextual based labeling technique has been successfully developed to address the insufficient functionalities of current labeling technique. Faculty of Engineering - School of Computing183http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:150777 Deep Learning Convolutional neural network (DL-CNN), Feature Extraction Network (FEN), Occluded Face Detection model (OFD

Computational Face Recognition Using Machine Learning Models

Faces are among the most complex stimuli that the human visual system processes. Growing commercial interest in face recognition is encouraging, but it also turns out to be a challenging endeavour. These challenges arise when the situations are complex and cause varied facial appearance due to e.g., occlusion, low-resolution, and ageing. The problem of computer-based face recognition using partial facial data is still largely an unexplored area of research and how does computer interpret various parts of the face. Another challenge is age progression and regression, which is considered to be the most revealing topic for understanding the human face changes during life. In this research, the various computational face recognition models are investigated to overcome the challenges posed by ageing and occlusions/partial faces. For partial face-based face recognition, a pre-trained VGGF model is employed for feature extraction and then followed by popular classifiers such as SVMs and Cosine Similarity CS for classification. In this framework, parts of faces such as eyes, nose, forehead, are used individually for training and testing. The results showing that there is an improvement in recognition in small parts, such as recognition rate in forehead enhanced form about 0% to nearly 35%, eyes from about 22% to approximately 65%. In the second framework, five sub-models were built based on Convolutional Neural Networks (CNNs) and those models are named Eyes-CNNs, Nose-CNNs, Mouth-CNNs, Forehead-CNNs, and combined EyesNose-CNNs. The experimental results illustrate a high recognition rate when it comes to small parts, for example, eyes increased up to about 90.83% and forehead reached about 44.5%. Furthermore, the challenge of face ageing is also approached by proposing an age-template based framework, generating an age-based face template for enhanced face generation and recognition. The results showing that generated new aged faces are more reliable comparing with state-of-the-art

Restoration and Domain Adaptation for Unconstrained Face Recognition

Face recognition (FR) has received great attention and tremendous progress has been made during the past two decades. While FR at close range under controlled acquisition conditions has achieved a high level of performance, FR at a distance under unconstrained environment remains a largely unsolved problem. This is because images collected from a distance usually suffer from blur, poor illumination, pose variation etc. In this dissertation, we present models and algorithms to compensate for these variations to improve the performance for FR at a distance. Blur is a common factor contributing to the degradation of images collected from a distance, e.g., defocus blur due to long range acquisition, motion blur due to movement of subjects. For this purpose, we study the image deconvolution problem. This is an ill-posed problem, and solutions are usually obtained by exploiting prior information of desired output image to reduce ambiguity, typically through the Bayesian framework. In this dissertation, we consider the role of an example driven manifold prior to address the deconvolution problem. Specifically, we incorporate unlabeled image data of the object class in the form of a patch manifold to effectively regularize the inverse problem. We propose both parametric and non-parametric approaches to implicitly estimate the manifold prior from the given unlabeled data. Extensive experiments show that our method performs better than many competitive image deconvolution methods. More often, variations from the collected images at a distance are difficult to address through physical models of individual degradations. For this problem, we utilize domain adaptation methods to adapt recognition systems to the test data. Domain adaptation addresses the problem where data instances of a source domain have different distributions from that of a target domain. We focus on the unsupervised domain adaptation problem where labeled data are not available in the target domain. We propose to interpolate subspaces through dictionary learning to link the source and target domains. These subspaces are able to capture the intrinsic domain shift and form a shared feature representation for cross domain recognition. Experimental results on publicly available datasets demonstrate the effectiveness of our approach for face recognition across pose, blur and illumination variations, and cross dataset object classification. Most existing domain adaptation methods assume homogeneous source domain which is usually modeled by a single subspace. Yet in practice, oftentimes we are given mixed source data with different inner characteristics. Modeling these source data as a single domain would potentially deteriorate the adaptation performance, as the adaptation procedure needs to account for the large within class variations in the source domain. For this problem, we propose two approaches to mitigate the heterogeneity in source data. We first present an approach for selecting a subset of source samples which is more similar to the target domain to avoid negative knowledge transfer. We then consider the scenario that the heterogenous source data are due to multiple latent domains. For this purpose, we derive a domain clustering framework to recover the latent domains for improved adaptation. Moreover, we formulate submodular objective functions which can be solved by an efficient greedy method. Experimental results show that our approaches compare favorably with the state-of-the-art