Sharif Digital Repository

In recent years, there has been a growing research interest in segmenting skin regions in color images. Skin segmentation aims at locating skin regions in an unconstrained input image. Skin detection is considered as an important preprocess in many applications such as face detection, face tracking, and filtering of objectionable web images. The most attractive properties of skin detection include low computational cost, increase of the total processing speed, and being invariance against rotation, scale, partial occlusion, and pose change. Because of the diversity of various image processing tasks, there exists no optimum method that can perform properly for all applications. Most of the... 

Panoramic radiography is known to be one of the preliminary means in diagnoses of maxillofacial intraosseos lesions, which has a big role in increasing the prognosis of such patients. Considering the fact that nowadays most health-care centers are equipped with digital radiography systems, we can rely on image processing techniques to recognize such lesions automatically.In this study, we try to segment mandible (lower jaw) out of panoramic image by means of some innovative algorithms based on edge detection and edge following, and some atlas-based methods. Then by extracting some features such as intensity, homogeneity, local energy and local gradient and with the help of SVM classifier we... 

Most broadcast stations insert their logos to claim video content ownership and/or for business purposes.This process reduces picture quality in the logo region and also causes visual discomfort to viewers. Logo detection has a variety of applications; such as automatic TV commercial removal, broadcast surveillance, and video content understanding. Video logos can be considered as a form of visible watermark. Stations may also overlay their logos over the original logo when rebroadcasting a program produced by another station. Also, most comapnies keep a giant archive of their broadcasted programs which are going to be used in their future programs. Here, we have presented an efficient... 

In this thesis we will first review the problem of deformable modeling. Due to their corss-disciplinary nature, deformable modeling techniques have been the subject of the vigorous research over the past three decades and have found numerous applications in the field of machine vision. Thus the focus will be on general deformable models for computer-based modeling which can be used for computer graphics, visualization, and various image processing applications. So the state of the art of deformable modeling is discussed. Then the focus of the thesis will be on different approaches for the problem of deformable surface reconstruction in 3D space. Amongs these methods there are two main... 

Nowadays, with high performance computers and progress in video recorder devices and their related technologies, price of these devices is being balanced and recording the videos is conventional now. Processing of these videos has been a challenge in industry and science. Control and surveillance of places such as airports and roads and reducing their sizes in memory are some of their research area. Usually one of the initial preprocesses of such applications specially the object tracking is background modeling and background subtraction. This preprocess has an essential effect on the other algorithms that process based on these processes’ results. If this section conducted with fewer... 

In many applications of multi view 3D reconstruction, image mosaicing is one of the most important processes. Image mosaicing is the action of stitching some pictures of a scene so that a complete picture of the scene is constructed. The proposed method is such that for PTZ cameras by extracting features from frame, the homography matrix between frames will be computed. Then by converting plane coordinate into spherical coordinate, a complete picture of the scene will be constructed and forground will be removed. For fixed cameras sufficient corresponding points will be selected for computing the homography matrix between cameras. Using the homography, the frames without forground will be... 

Image Registration is a fundamental task in numerous applications in medical image processing and is defined as the process of determining the correspondence of between images collected at different times or using different imaging modalities. This correspondence can be used for aligning images so that the pair can be directly compared, combined or analyzed. Image-guided surgery systems use registration for establishing an accurate relation between preoperative and intraoperative image space. There have been several methods for rigid registration which are not easily applicable for soft tissues. Indeed, nonrigid deformation of soft tissues will endanger the accuracy of rigid methods, so it... 

In recent years, ability of computers to recognize human actions, because of numerousapplications, has attracted scientists. Surveillancesystems in house, work and public places, human computer interaction, study of human movement problems, remote supervision of ill or old people and sport training are only some of the applications. In this thesis 10 actions are considered. These actions are Walking, Running, Galloping side, Bending, Jump jacking, Jumping, Jumping in place, Skipping, Waving one hand and Waving two hands. All actions exist in Weisemann dataset so this dataset is used as training and testing dataset. Here important objectives are recognising human action so that it is... 

In large databases, availability of labeled training data is mostly prohibitive in classification. Semi-supervised algorithms are employed to tackle the lack of labeled training data problem. Video databases are the epitome for such a scenario; that is why semi-supervised learning has found its niche in it. Graph-based methods are a promising platform for semi-supervised video classification. Based on the multiview characteristic of video data, different features have been proposed (such as SIFT, STIP and MFCC) which can be utilized to build a graph. In this project, we have proposed a new classification method which fuses the results of manifold regularization over different graphs. Our... 

The goal of human action recognition systems is to label the sensory observation data, using one of the predefined action verbs in the system. During recent years, human action recognition has received a growing interest due to its application in automatic scene interpretation. For instance, automatic surveillance systems in public places should be able to discriminate normal and suspicious actions. Human-computer-interface (HCI) systems (which have became popular in recent years) mostly need a similar system to recognize the gesture of their users without using any keyboard (or similar input devices). Human action recognition technologies can also boost the video retrieval systems.
An... 

One major problem in sport match analysis and interpretation is that there are restricted viewpoints of the game. 3D reconstruction allows us to have virtual replay from any viewpoint so that the events such as penalties can be detected easily. For achieving this purpose, we use many cameras with overlapped views that cover almost all parts of the field. After some preprocessing, 3D reconstruction and texture mapping, we can enhance the viewer experience by having arbitrary viewpoint of the match. In this research, we use two different visual hull methods for 3D reconstruction. In the first method, the visual hull of an object is computed efficiently and robustly from image contours. This... 

Object recognition is a field of image processing with the purpose of object detection and determining its pose. There was a wide research of object recognition using 2d information. These methods are less efficient due to their sensitivity to view and scale. Today with development of 3d technology, 3d reconstruction of objects has been eased, thus there is a new trend of 3d methods. 3d object recognition uses 3d data and model to recognize objects more efficiently in different views and in occlusion and clutter. The related works are classified in three category of view-based, feature matching, and classification. In this research we attempted to improve one of the best feature matching... 

Today, advances in technology caused the emergence of a need for intelligent systems which can operate without human supervision, and have variety of applications in security, industry, transportation and sport events. Most of these systems require faster and more accurate object tracking. Lots of surveillance and computer vision applications need a process to detect and track objects. For example, the exact location of objects or people is part of the input for applications like movement analysis, counting the number of items, and recognition of people’s behavior. Occlusion is one of the major obstacles in performance of auto-tracking systems. There are several methods to address this... 

During past decade, human pose estimation has become a very important topic in computer vision with many applications; such as robotic, human computer interaction, and analyzing sport videos. Pose estimation is the process of estimating the configuration of the body joints from one or more images. Pose estimation in 2D space has been performed by processing of the images of a single camera. Recently, the multi-view methods have been emerged to estimate 3D human pose.The purpose of this thesis is 3D human pose estimation from multi-view images, captured in football matches. Pictorial structure is an efficient method in 2D human pose estimation. The 3D extension of this method is studied in... 

Simultaneous localization and mapping (SLAM) is the action of detecting robot pose in an unknown environment and building the environment map by use of input data that captured from robot sensors. In visual SLAM, the input data for the robot, is limited to camera sensors. Nowadays, SLAM is one of the main challenges in robotic research.For autonomous action, we need robot pose in the map of the environment. The map production in the indoor environment, there is no GPS data, is one of the research issue in robotic community, in last decade. In this thesis, a new and efficient method is proposed for SLAM at the level of objects. The maps produced by state of the art methods don’t have a... 

Nowadays TV broadcasting of soccer matches has attracted a lot of viewers. With advancement of technology, the broadcasting is also going under changes. One of these changes is using free-viewpoint video. In free-viewpoint video users can interactively choose any view to watch the match from. Generally free-viewpoint problem is defined as follows. We have sequential frames of a soccer match video from different views as input. We want to create sequential frames of the same video from a different view as output. There are several methods for solving this problem. We can classify these methods into to general approaches. Image-based and geometry-based. We will examine these approaches in... 

Camera calibration in sport videos has applications such as sport video analysis, insertion of virtual graphical elements, and 3D reconstruction. Our goal in this research is to fully calibrate cameras in soccer match videos. By calibration parameters, we mean the internal and the external camera parameters. We can have a mapping from world coordinates to image coordinates if we have all the calibration parameters. The cameras used in this research are stationary pan-tilt-zoom cameras. The main challenges in camera calibration are noise, blur, bad lighting conditions, lack of useful information image,fast movement of camera and radial distortion. In addition, as another challenge, we assume... 

Fine-grained image classification is image classification where the considered classes are all sub-classes of a certain, more general class. In this setting of the problem, the classes are visually very similar to each other, such that an unskilled human cannot discriminate between them. In this case, proposed methods for the ordinary image classification problem do not obtain good classification accuracy. So proposing new methods for solving this problem is necessary. In this thesis two new methods, based on recent advances in deep learning are proposed for solving the fine-grained image classification problem. First by improving several parts of one of the recent proposed methods for this... 

In computer vision literature, tracking problems are considered to be among the open and sophisticated issues. 3D object tracking is also an interesting problem which not only needs knowledge in computer vision, but it also requires knowledge of 3D geometry. Tracking soccer ball as a small and speedy obejct with PTZ cameras has several challenges such as blurring, blocking and getting lost. In this thesis, we aim to solve these issues with detection and learning frameworks. Current methods in tracking soccer balls usually exploit heuristic features, which as a result, creates dependency on the problem and its data type. Also, since ball tracking problem is directly related to the sports... 

Hand gesture recognition is one of the most applicable and hot research topics in computer vision community. The recent advances in imaging devices, like Microsoft Kinect, have received a great deal of attention from researchers to reconsider problems such as gesture recognition from depth information. Hand gesture recognition refers to the classification of dynamic hand movements in action videos. Generally, hand gesture recognition includes three main steps: hand detection, feature extraction and classification. The first step plays an important role in hand gesture recognition. The most challenging part of hand gesture recognition is the second step which is the process of extracting high...