692 research outputs found
Enhanced iris recognition: Algorithms for segmentation, matching and synthesis
This thesis addresses the issues of segmentation, matching, fusion and synthesis in the context of irises and makes a four-fold contribution. The first contribution of this thesis is a post matching algorithm that observes the structure of the differences in feature templates to enhance recognition accuracy. The significance of the scheme is its robustness to inaccuracies in the iris segmentation process. Experimental results on the CASIA database indicate the efficacy of the proposed technique. The second contribution of this thesis is a novel iris segmentation scheme that employs Geodesic Active Contours to extract the iris from the surrounding structures. The proposed scheme elicits the iris texture in an iterative fashion depending upon both the local and global conditions of the image. The performance of an iris recognition algorithm on both the WVU non-ideal and CASIA iris database is observed to improve upon application of the proposed segmentation algorithm. The third contribution of this thesis is the fusion of multiple instances of the same iris and multiple iris units of the eye, i.e., the left and right iris at the match score level. Using simple sum rule, it is demonstrated that both multi-instance and multi-unit fusion of iris can lead to a significant improvement in matching accuracy. The final contribution is a technique to create a large database of digital renditions of iris images that can be used to evaluate the performance of iris recognition algorithms. This scheme is implemented in two stages. In the first stage, a Markov Random Field model is used to generate a background texture representing the global iris appearance. In the next stage a variety of iris features, viz., radial and concentric furrows, collarette and crypts, are generated and embedded in the texture field. Experimental results confirm the validity of the synthetic irises generated using this technique
2D Mapping of strongly deformed cell nuclei based on contour warping
The dynamics of genome regions are associated to the functional or dysfunctional behaviour of the human cell. In order to study these dynamics it is necessary to remove perturbations coming from movement and deformation of the nucleus, i.e. the container holding the genome. In literature models have been proposed to cope with the transformations corresponding to nuclear dynamics of healthy cells. However for pathological cells, the nucleus deforms in an apparently random way, making the use of such models a non trivial task. In this paper we propose a mapping of the cell nucleus which is based on the matching of the nuclear contours. The proposed method does not put constraints on the possible shapes nor on the possible deformations, making this method suited for the analysis of pathological nuclei
Manifold Learning for Natural Image Sets, Doctoral Dissertation August 2006
The field of manifold learning provides powerful tools for parameterizing high-dimensional data points with a small number of parameters when this data lies on or near some manifold. Images can be thought of as points in some high-dimensional image space where each coordinate represents the intensity value of a single pixel. These manifold learning techniques have been successfully applied to simple image sets, such as handwriting data and a statue in a tightly controlled environment. However, they fail in the case of natural image sets, even those that only vary due to a single degree of freedom, such as a person walking or a heart beating. Parameterizing data sets such as these will allow for additional constraints on traditional computer vision problems such as segmentation and tracking. This dissertation explores the reasons why classical manifold learning algorithms fail on natural image sets and proposes new algorithms for parameterizing this type of data
Weakly Supervised Geodesic Segmentation of Egyptian Mummy CT Scans
In this paper, we tackle the task of automatically analyzing 3D volumetric
scans obtained from computed tomography (CT) devices. In particular, we address
a particular task for which data is very limited: the segmentation of ancient
Egyptian mummies CT scans. We aim at digitally unwrapping the mummy and
identify different segments such as body, bandages and jewelry. The problem is
complex because of the lack of annotated data for the different semantic
regions to segment, thus discouraging the use of strongly supervised
approaches. We, therefore, propose a weakly supervised and efficient
interactive segmentation method to solve this challenging problem. After
segmenting the wrapped mummy from its exterior region using histogram analysis
and template matching, we first design a voxel distance measure to find an
approximate solution for the body and bandage segments. Here, we use geodesic
distances since voxel features as well as spatial relationship among voxels is
incorporated in this measure. Next, we refine the solution using a GrabCut
based segmentation together with a tracking method on the slices of the scan
that assigns labels to different regions in the volume, using limited
supervision in the form of scribbles drawn by the user. The efficiency of the
proposed method is demonstrated using visualizations and validated through
quantitative measures and qualitative unwrapping of the mummy
Rõivaste tekstureerimine kasutades Kinect V2.0
This thesis describes three new garment retexturing methods for FitsMe virtual fitting room applications
using data from Microsoft Kinect II RGB-D camera.
The first method, which is introduced, is an automatic technique for garment retexturing using
a single RGB-D image and infrared information obtained from Kinect II. First, the garment
is segmented out from the image using GrabCut or depth segmentation. Then texture domain
coordinates are computed for each pixel belonging to the garment using normalized 3D information.
Afterwards, shading is applied to the new colors from the texture image.
The second method proposed in this work is about 2D to 3D garment retexturing where a segmented
garment of a manikin or person is matched to a new source garment and retextured,
resulting in augmented images in which the new source garment is transferred to the manikin
or person. The problem is divided into garment boundary matching based on point set registration
which uses Gaussian mixture models and then interpolate inner points using surface
topology extracted through geodesic paths, which leads to a more realistic result than standard
approaches.
The final contribution of this thesis is by introducing another novel method which is used for
increasing the texture quality of a 3D model of a garment, by using the same Kinect frame
sequence which was used in the model creation. Firstly, a structured mesh must be created
from the 3D model, therefore the 3D model is wrapped to a base model with defined seams and
texture map. Afterwards frames are matched to the newly created model and by process of ray
casting the color values of the Kinect frames are mapped to the UV map of the 3D model
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