Search for: edge-detection
0.009 seconds
Total 40 records

    Fundamental limit for gain and resolution in analog optical edge detection

    , Article Optics Express ; Volume 28, Issue 2 , 2020 , Pages 898-911 Karimi, P ; Khavasi, A ; Mousavi Khaleghi , S. S ; Sharif University of Technology
    OSA - The Optical Society  2020
    In this paper, the relation between gain and resolution of an ideal analog optical differentiator in two different cases and their fundamental limits are investigated. Based on this relation, a figure of merit for comparison of the designed differentiators in recent papers is proposed. The differentiators are optimized using this figure of merit, and they are compared with each other to determine the best one. Also, a new differentiator is presented based on the dielectric slab waveguide in which the trade-off between its gain and resolution is easily controllable, and its best operating point is determined. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing... 

    Robust zero watermarking for still and similar images using a learning based contour detection

    , Article Communications in Computer and Information Science ; Vol. 427, issue , Sep , 2014 , p. 13-22 Ehsaee, S ; Jamzad, M ; Sharif University of Technology
    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 reduces 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 paper 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. Experimental... 

    Monocular 3D Human Pose Estimation with a Semi-supervised Graph-Based Method

    , Article 2015 International Conference on 3D Vision, 3DV 2015, 19 October 2015 through 22 October 2015 ; October , 2015 , Pages 518-526 ; 9781467383325 (ISBN) Abbasi, M ; Rabiee, H. R ; Gagne, C ; Brown M ; Kosecka J ; Theobalt C ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    In this paper, a semi-supervised graph-based method for estimating 3D body pose from a sequence of silhouettes, is presented. The performance of graph-based methods is highly dependent on the quality of the constructed graph. In the case of the human pose estimation problem, the missing depth information from silhouettes intensifies the occurrence of shortcut edges within the graph. To identify and remove these shortcut edges, we measure the similarity of each pair of connected vertices through the use of sliding temporal windows. Furthermore, by exploiting the relationships between labeled and unlabeled data, the proposed method can estimate the 3D body poses, with a small set of labeled... 

    The eyelids distance detection in gray scale images

    , Article 2006 International Symposium on Communications and Information Technologies, ISCIT, Bangkok, 18 October 2006 through 20 October 2006 ; 2006 , Pages 937-940 Fathi, A. H ; Mohammadi, F. A ; Manzuri, M. T ; Sharif University of Technology
    in this paper a new method for finding the distance between eyelids, in order to determine the open or closed state of eye, has been introduced. For this aim, first the gray scale image of eye region is converted into a binary image. Next, a differential variance projection function is applied on the binary image of eye region in horizontally direction to show the uppermost and lowest points on the eyelid edges. Having the distance between these two points, the distance between two eyelids will be obtained. This distance may be used as a criterion in recognizing the open or closed state of eye. We have used numerous and different images to evaluate the efficiency of the presented method, and... 

    Multicolored parallelisms of isomorphic spanning trees

    , Article SIAM Journal on Discrete Mathematics ; Volume 20, Issue 3 , 2006 , Pages 564-567 ; 08954801 (ISSN) Akbari, S ; Alipour, A ; Fu, H. L ; Lo, Y. H ; Sharif University of Technology
    A subgraph in an edge-colored graph is multicolored if all its edges receive distinct colors. In this paper, we prove that a complete graph on 2m (m ≠ 2) vertices K2m can be properly edge-colored with 2m - 1 colors in such a way that the edges of K2m can De partitioned into m multicolored isomorphic spanning trees. © 2006 Society for Industrial and Applied Mathematics  

    Two-dimensional edge detection by guided mode resonant metasurface

    , Article IEEE Photonics Technology Letters ; Volume 30, Issue 9 , 1 May , 2018 , Pages 853-856 ; 10411135 (ISSN) Saba, A ; Tavakol, M. R ; Karimi Khoozani, P ; Khavasi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    In this letter, a new approach to perform edge detection is presented using an all-dielectric complimentary metal-oxide-semiconductor-compatible metasurface. Our design is based on the guided-mode resonance, which provides a high quality factor resonance to make the edge detection experimentally realizable. The proposed structure is easy to fabricate, and it can be exploited for detection of edges in two dimensions due to its symmetry. In addition, a tradeoff between gain and the resolution of edge detection is discussed, which can be adjusted using appropriate design parameters. The proposed edge detector potentially can be used in ultrafast analog computing and image processing. ©... 

    Spectral redundancy compensation in multi-static millimeter-wave imaging

    , Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Volume 65, Issue 5 , May , 2018 , Pages 687-691 ; 15497747 (ISSN) Kazemi, M ; Shabany, M ; Kavehvash, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    This brief introduces a modified backprojection algorithm to compensate the effect of redundancy of captured data in spatial-fourier or k-space domain for multi-static millimeter-wave imaging. The data measured by each transmitter-receiver pair is explained in k-space domain and the redundancies are determined. Such redundancies act as an undesirable filter that distorts the appearance of the resulting image. Our goal is to modify SAR backprojection algorithm to address this problem, where extensive simulation and experimental results are also provided. Our measurements show a significant improvement in the overall quality and edge preservation in the reconstructed image of objects under the... 

    Image Edge Detection Using Ant Algorithms

    , M.Sc. Thesis Sharif University of Technology Moradi Davijani, Hossein (Author) ; Mahdavi - Amiri, Nezameddin (Supervisor)
    Ant algorithms are optimization algorithms inspired by natural behavior of real ants, which can find the shortest path between nest and food. These algorithms are used to solve numerous complex optimization and combinatorial problems. In recent years, ant algorithms have been used in image processing, specially in edge detection. Edge detection being important and having applications in image processing, several edge detection algorithms have been presented. Our goal is to study edge detection processes based on ant algorithms. Four algorithms recently proposed in the literature are implemented, and the results presented by their authors are verified. Furthermore, implemented algorithms are... 

    A robust zero-watermarking scheme using Canny edge detector

    , Article International Journal of Electronic Security and Digital Forensics ; Volume 5, Issue 1 , 2013 , Pages 25-44 ; 1751911X (ISSN) Shakeri, M ; Jamzad, M ; Sharif University of Technology
    By expansion of digital multimedia and networking technology, the problem of ownership protection has become increasingly important. Digital watermarking is an efficient way for copyright protection of digital images. Traditional watermarking techniques degrade the quality of host image by embedding a watermark logo. Facing this problem, a new watermarking approach called zero-watermarking has been proposed. In zero-watermarking methods, the watermark does not require to be embedded into the protected image but it uses both the watermark and the protected image to generate a verification map which is registered to a trusted authority for further protection. In this paper we propose a robust... 

    Configurable ultrasonic flaw classification of oil pipelines

    , Article Nondestructive Testing and Evaluation ; Volume 23, Issue 1 , 2008 , Pages 43-55 ; 10589759 (ISSN) Ravanbod, H ; Jalali, A ; Sharif University of Technology
    To make a decision on the nature of a flaw within a pipeline, it is necessary to detect suspicious regions in ultrasonic inspection images reliably and to, derive geometrical parameters such as shape, position and orientation from each measured signal and finally to collate these parameters intelligently by associating each measured signal with a possible flaw type. These two papers present an innovative method of configurable flaw classification and volume estimation in oil pipelines. This method includes: (1) An adaptive thresholding selection for estimation of the area and volume of the flaws, (2) Dynamic detection of interesting points as feature points at different levels of images by... 

    An efficient features-based license plate localization method

    , Article 18th International Conference on Pattern Recognition, ICPR 2006, Hong Kong, 20 August 2006 through 24 August 2006 ; Volume 2 , 2006 , Pages 841-844 ; 10514651 (ISSN); 0769525210 (ISBN); 9780769525211 (ISBN) Mahini, H ; Kasaei, S ; Dorri, F ; Sharif University of Technology
    This paper presents a feature-based license plate localization algorithm that copes with multi-object problem in different image capturing conditions. The proposed algorithm is robust against illumination, shadow, scale, rotation, and weather condition. It extracts license plate candidates using edge statistics and morphological operations and removes the incorrect candidates according to the determined features of license plates. We have formed a rather complete database of 269 images in different conditions. The proposed algorithm successfully detecteds the accurate location of the license plates in 96.5% cases, which outperforms the other available approaches in the literature. © 2006... 

    All-Optical Signal Processing Using Compact Photonic Devices

    , M.Sc. Thesis Sharif University of Technology Pour Mohammad Qoli Vafa, Ali (Author) ; Khavasi, Amin (Supervisor)
    Digital computers, comprising universal logic gates, are tremendously versatile. This versatility associated with the increasing integrability of digital electronics due to Moore’s law has left nearly no room for analog computers in the last few decades. However, in the case of some specific problems such as modeling complex and nonlinear systems or pro-cessing large amounts of data, computation time and power is still a serious restriction of digital computing. Optical phenomena are fast enough and offer novel approaches to overcome the mentioned restrictions about the system speed and power consumption. Therefore, optical structures make possible to perform ultra-fast spatial analog... 

    Using Visual Patterns for Precise Automatic Landing of a Quadcopter

    , M.Sc. Thesis Sharif University of Technology Noorian, Hamid Reza (Author) ; Nobahari, Hadi (Supervisor)
    In this study, the method of recognizing image patterns by image processing to guide the quadcopter to the landing point is expressed. For this, first the forces and torques on the quadcopter in the body system are calculated and after transferring to the inertial coordinates, the quadcopter dynamics with the use of Newton-Euler law is simulated in the MATLAB software environment. Then, a simple PID controller is designed to control the attitude, height and position of the quadcopter and create stability in the quadcopter dynamics. Because quadcopter navigation is dependent on visual data, a simulation environment called VRML is used. This environment has the ability to create a... 

    Memristive fuzzy edge detector

    , Article Journal of Real-Time Image Processing ; Vol. 9, issue. 3 , September , 2014 , pp. 479-489 ; Online ISSN: 1861-8219 Merrikh-Bayat, F ; Bagheri Shouraki, S ; Merrikh-Bayat, F ; Sharif University of Technology
    Fuzzy inference systems always suffer from the lack of efficient structures or platforms for their hardware implementation. In this paper, we tried to overcome this difficulty by proposing a new method for the implementation of the fuzzy rule-based inference systems. To achieve this goal, we have designed a multi-layer neuro-fuzzy computing system based on the memristor crossbar structure by introducing a new concept called the fuzzy minterm. Although many applications can be realized through the use of our proposed system, in this study we only show how the fuzzy XOR function can be constructed and how it can be used to extract edges from grayscale images. One main advantage of our... 

    Multi-directional spatial error concealment using adaptive edge thresholding

    , Article IEEE Transactions on Consumer Electronics ; Volume 58, Issue 3 , 2012 , Pages 880-885 ; 00983063 (ISSN) Asheri, H ; Rabiee, H ; Pourdamghani, N ; Ghanbari, M ; Sharif University of Technology
    In this paper, a new method for spatial concealment of missing areas in image and video signals transmitted over error prone infrastructures, is presented. The concealment process is performed in three steps. First, a novel technique is used to estimate the significant edges of missing areas after performing a directional edge analysis on the correctly received neighboring blocks of the missing areas. This technique uses the moments of the neighboring edge magnitudes to obtain an adaptive threshold for rejecting non-significant directions. Second, based on the predicted significant directions, an approximation is obtained for each missing pixel. Finally, for each pixel, we compute a weighted... 

    Audio image rendering for the severely visually impaired

    , Article 2009 IEEE International Conference on Rehabilitation Robotics, ICORR 2009, Kyoto, 23 June 2009 through 26 June 2009 ; 2009 , Pages 893-898 ; 9781424437894 (ISBN) Hajipour, S ; Khosravi, N ; Zahedi, E ; Sharif University of Technology
    In this paper, a solution is proposed to render both rough and detailed images information using only audio-range sound. The procedure is implemented in consecutive stages with stage-dependent parameters selected by the user. The first stage consists of edge detection and tracking of the boundaries of the objects to obtain the sketch of the image. In the second stage, the user can selectively access the details of the image, such as brightness, texture and spatial position of the objects. Practical methods are proposed and tested which accelerate the training process. As a particular application, an educational module is presented which assists students of a special school for the blind by... 

    Video cut detection in E-learning applications

    , Article 2007 9th International Symposium on Signal Processing and its Applications, ISSPA 2007, Sharjah, 12 February 2007 through 15 February 2007 ; 2007 ; 1424407796 (ISBN); 9781424407798 (ISBN) Koohi, S ; Babagoli, M ; Lotfi, T ; Kasaei, S ; Sharif University of Technology
    Real-time video transmission is considered as an important means for information distribution. One major application of it is E-learning, which requires real-time video processing and transmission. On the other hand, the process of cut detection is a fundamental component in automatic video browsing, indexing, searching, retrieval, and archiving. This paper introduces a new video cut detection technique that uses dominant lines and angles extracted from edge information of the video contents. To the best of our knowledge, it is the first works done for cut detection in E-learning application. This method is compatible with our application's requirements and has a low complexity and high... 

    Improving the quality of active millimeter wave standoff imaging by incorporating the cross-polarized scattering wave

    , Article Optics Express ; Volume 29, Issue 20 , 2021 , Pages 32603-32614 ; 10944087 (ISSN) Shojaeian, S ; Ahmadi Boroujeni, M ; Hajitabarmarznaki, S ; Sharif University of Technology
    The Optical Society  2021
    In this paper, we study the feasibility of incorporating the cross-polarized scattered wave in active standoff millimeter-wave imaging in order to improve the edge detection and background suppression for metallic objects. By analyzing the scattering from a perfectly conducting (PEC) patch of a simple geometrical shape we show that the edge diffraction is the major source of cross-polarized scattering. A similar scattering behavior is also observed for a PEC patch placed on a dielectric medium. Hence, the cross-polarized scattered field conveys valuable information about the edges of the object. In addition, the cross-polarized scattering can be utilized to resolve the object from an... 

    Composition of MPEG-7 color and edge descriptors based-on human vision perception

    , Article Visual Communications and Image Processing 2005, Beijing, 12 July 2005 through 15 July 2005 ; Volume 5960, Issue 1 , 2005 , Pages 568-575 ; 0277786X (ISSN) Lakdashti, A ; Kialashaki, N ; Ghonoodi, A ; Soltani, M ; Sharif University of Technology
    In content based image retrieval similarity measurement is one of the most important aspects in a large image database for efficient search and retrieval to find the best answer for a user query. Color and texture are among the more expressive of the visual features. Considerable work has been done in designing efficient descriptors for these features for applications such as similarity retrieval. The MPEG-7 specifies a standard set of descriptors for color, texture and shape. In the Human Vision System (HVS), visual information is not perceived equally; some information may be more important than other information. The purpose of this paper is to show how the MPEG-7 descriptor based on... 

    Unique list-colourability and the fixing chromatic number of graphs

    , Article Discrete Applied Mathematics ; Volume 152, Issue 1-3 , 2005 , Pages 123-138 ; 0166218X (ISSN) Daneshgar, A ; Hajiabolhassan, H ; Sharif University of Technology
    In this paper we introduce a chromatic parameter, called the fixing chromatic number, which is related to unique colourability of graphs, in the sense that it measures how one can embed the given graph G in G∪Kt by adding edges between G and Kt to make the whole graph uniquely t-colourable. We study some basic properties of this parameter as well as its relationships to some other well-known chromatic numbers as the acyclic chromatic number. We compute the fixing chromatic number of some graph products by applying a modified version of the exponential graph construction. © 2005 Elsevier B.V. All rights reserved