Sharif Digital Repository

Shadows are one of the most important details in graphical images. There exist many shadow generation algorithms each of which suffers from some problems. High processing time and ill-shaped shadow borders, known as alasing, are some of such problems. In this paper, we propose a heuristic method based on standard shadow map technique, named rotated shadow maps, to generate excellent hard shadows. Our method uses some shadow maps which are generated from the same view but objects are slightly rotated around the center of view area. Rotated shadow maps can be considered as an independent hard shadow generation algorithm. Also it can be combined with other shadow map based approaches. Utilizing... 

To overcome challenges such as object appearance changes and environment illumination variations in tracking methods, online algorithms are suggested to be used instead of offline ones. Online algorithms update the model by the information acquired in the last processed frame. The main challenge of using online algorithms is the accumulation of small errors after several steps of updating of the model (drift) which disturbs the model and causes tracking failure. Using the object information in the first frame in each update can be considered as a solution. The proposed online semi-supervised boosting algorithms can overcome the drift problem at the expense of decreasing their capabilities in... 

Detecting emotions and facial expressions, as a means of nonverbal communication between human and machines, has attracted a great deal of attention in recent decades with the developments in artificial intelligence and acknowledging the ties between robotics and future human life. Human face plays a key role in his communications and processing it in a video source for the sake of mood recognition could be employed in different applications such as improving human and machine communication and analysis of emotions in different circumstances. Facial expression detection is useful in understanding not only momentary emotions, but also mental activities, social interactions and psychological... 

Nowadays the number of digital images has largely increased because of progress in internet technology. Management of this volume of data needs an efficient system for browsing, categorizing, and searching the images. The goal of this research is to design a system for automatic annotation of unobserved images for better search in image data bases. Automatic image annotation is a multi-label classification problem with many labels which suggests some words for describing the content of an image. Designing AIA systems faces chanllenges like semantic gap between low level image features and high level human expressions (tags), incompelete tags and imbalance images per tags in the datasets.... 

The Gaussian mixture (cardinalized) probability hypothesis density (GM-(C)PHD) filter is a closed form approximation of multi-target Bayes filter which can overcome most of multi-target tracking problems. Limited field of view, decreasing cost of cameras and its advances induce us to use large-scale camera networks. Increasing the size of camera networks make centralized networks practically inefficient. On the other hand, scalability, simplicity and low data transmission cost has made distributed networks a good replacement for centralized networks. However, data fusion in distributed network is sub-optimal due to unavailable cross-correlation.Among data fusion algorithms which deal with... 

With the advances in technology, Nowadays digital cameras are everywhere. As a result very large amount of images are on the web. Searching through these images intelligently and purposively is an essential need. Recently the possibility of retrieving images with some conceptual words along side of content based image retrieval has been studied in computer vision. For this purpose it’s required that for each image several words that describe its content be assigned automatically. One of the main problems for this task is semantic gap, meaning that the low level features such as color, texture,… don’t have the ability to describe the high level concepts in images which are comprehensible by... 

Nowadays, digital images are easy to manipulate and edit due to availability of powerful image processing and editing software. It is possible to add or remove important features to the image without leaving any obvious traces of tampering. Therefore, proving the authenticity and integrity of digital media becomes increasingly important. In this study, we focus on detection of a special type of digital forgery, the copy-move attack, in which a part of the image is copied and pasted somewhere else in the image with the intent to cover an important image features or to add some fake feature. In this way we propose some novel methods that work in spatial domain, Discrete Cosine domain and... 

Brain cancer is a lump or tumor in the brain caused by abnormal growth of cells. Glioma is a common type of tumor that develops in the brain. In order to plan precise treatment or accurate tumor removal surgery, brain tumor segmentation is critical for detecting all parts of tumor and its surrounding tissues. To visualize the brain anatomy and detect its abnormalities, we use Magnetic Resonance Imaging (MRI) as an input. Due to many differences in the shape and appearance, accurate segmentation of glioma for identifying all parts of the tumor and its surrounding tissues in cancer detection is a challenging task. Moreover, due to the intensity inhomogeneity existing in brain MRI and gray... 

Sign Language Recognition using cameras is an alternative way of human communication with personal computers. These systems don’t need to use keyboard. They are used when touching keyboard is not possible or for what ever reason, when we don’t want to use keyboard. In this problem the person shows one of the alphabets with his hand and we capture and process that in real-time to recognize the letter. The problem of previous works in this area are the decreasing rate of detection in condition where the angle of sign and viewer changes. The purpose of our work is getting better result by using depth image from Kinect. We use Pugeault and Bowden dataset (that has fingerspelling sign in multiple... 

Motion planning in an autonomous vehicle is responsible for providing smooth, safe and efficient actions. Besides reducing the risk of collision with static and moving obstacles, the ability to make suitable decisionsencountering sudden changes in environment is very important. Many solutions for dealing this problem have been offered, one of which is, Artificial Potential Fields (APF). APF is a simple and computationally low cost method which keeps the robot away from the obstacles in the environment. However, this approach suffers from trapping in local minima’s of potential function and then fails to produce a plan. Furthermore,Oscillation in presence of obstacles or in narrow passages... 

The advent of digital age with the Internet revolution has made it extremely convenient for users to access, create, process, copy, or exchange multimedia data. This has created an urgent need for protecting intellectual property in both the digital and the print media. Digital watermarking is a suitable way to do this. In this technology, some hidden information called watermark are embedded into host signal and extracted to confirm copyright protection. However, the watermark should be embedded in the host in such a way that the attacks could not destroy it. Print and scan is a popular attack that is applied on digital images. This attack has complex nature and can be implemented easily.... 

Aautomatic image annotation that assigns some labels to input images and provides a textual description for the contents of images has become an active field in machine vision community. To design an annotation system, we need a dataset that contains images and labels for them. However, a large amount of manual efforts is required to annotate all images in a dataset. To reduce the demand of annotation systems on the labeled images, one solution is to exploit useful information embedded into the unlabeled images and incorporate them into learning process. In machine learning community, semi-supervised learning (SSL) has been introduced with the aim of incorporating unlabeled samples into the... 

Recently many works has been focused on Automatic Security Systems. Car type and color recognition systems are needed in vehicle based access control systems in buildings, outdoor sites and even housing estates. Another usage of car type and color recognition is when a certain model of car is being investigated in highways and streets. In this thesis two independent systems are designed; one for car type recognition and another for car color recognition. They both require to know the license plate location, so we proposed a license plate detection system. In the license plate detection system, first the plate candidates are extracted from image by gradient and morphological operations, then... 

Digital watermarking is an efficacious technique to protect the copyright and ownership of digital information. Traditional image watermarking algorithms embed a logo in the image that could reduce its visual quality. A new approach in watermarking called zero watermarking doesn’t need to embed a logo in the image. In this algorithm we find a feature from the main image and combine it with a logo to obtain a key. This key is securely kept by a trusted authority. In this thesis we show that we can increase the robustness of digital zero watermarking by a new counter detection method in comparison to Canny Edge detection and morphological dilatation that is mostly used by related works.... 

Steganalysis is the art of detecting hidden message in a cover such as an image. All steganalysis methods either are designed for a specific steganographer or are blind. Since for a stego image, the steganography method is not available, this is important to detect a stego image without any knowledge about the steganography method using which the secret image was embedded. Therefore in order to dominate all steganography method, if a given image is a stego one, we need to use voting over several steganalysis methods applied on the stego image to improve the accuracy of detection. But this approach needs a long time to process that is not practical for most steganalysis applications. We know... 

Human activity recognition is an important and useful area in computer vision that application include surveillance systems, patient monitoring systems, human-computer interaction and analyse video data from big websites.Traditional Human action recognition use the RGB videos as default input that unable describe motion and action as full. On the other hand Kinect camera sendsthe RGB data to output in addition to the Depth Data that allows us to extract skeleton of human easily. Recently Space-time features have been particulary popular in RGB Videos because of their structure. These features are describedby their descriptor and send the good and important information to output.Finally we...