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  • 1. Blomstrand, F
    et al.
    Khatibi, Siamak
    Muyderman, H
    Olsson, T
    Rönnbäck, L
    Calcium wave communication within the astroglial network via gap junctions1997In: On astrocytes and glutamate neurotransmission: New waves in brain information processing, Springer, R.G. Landes Company , 1997, p. 121-153Chapter in book (Refereed)
  • 2.
    Chen, Jiandan
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Khatibi, Siamak
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Kulesza, Wlodek
    Blekinge Institute of Technology, School of Engineering, Department of Electrical Engineering.
    Depth reconstruction uncertainty analysis and improvement: The dithering approach2010In: Image and Vision Computing, ISSN 0262-8856, E-ISSN 1872-8138, Vol. 29, no 9, p. 1377-1385Article in journal (Refereed)
    Abstract [en]

    The depth spatial quantization uncertainty is one of the factors which influence the depth reconstruction accuracy caused by a discrete sensor. This paper discusses the quantization uncertainty distribution, introduces a mathematical model of the uncertainty interval range, and analyzes the movements of the sensors in an Intelligent Vision Agent System. Such a system makes use of multiple sensors which control the deployment and autonomous servo of the system. This paper proposes a dithering algorithm which reduces the depth reconstruction uncertainty. The algorithm assures high accuracy from a few images taken by low-resolution sensors. The dither signal is estimated and then generated through an analysis of the iso-disparity planes. The signal allows for control of the camera movement. The proposed approach is validated and compared with a direct triangulation method. The simulation results are reported in terms of depth reconstruction error statistics. The physical experiment shows that the dithering method reduces the depth reconstruction error.

  • 3. Chen, Jiandan
    et al.
    Khatibi, Siamak
    Kulesza, Wlodek
    Planning of a Multi Stereo Visual Sensor System Depth Accuracy and Variable Baseline Approach2007Conference paper (Refereed)
  • 4. Chen, Jiandan
    et al.
    Khatibi, Siamak
    Kulesza, Wlodek
    Planning of a Multi Stereo Visual Sensor System for a Human Activities Space2007Conference paper (Refereed)
  • 5. Chen, Jiandan
    et al.
    Khatibi, Siamak
    Wirandi, Jenny
    Kulesza, Wlodek
    Planning of a Multi Sensor System for Human Activities Space – Aspects of Iso-disparrity Surface2007Conference paper (Refereed)
    Abstract [en]

    The Intelligent Vision Agent System, IVAS, is a system for automatic target detection, identification and information processing for use in human activities surveillance. This system consists of multiple sensors, and with control of their deployment and autonomous servo. Finding the optimal configuration for these sensors in order to capture the target objects and their environment to a required specification is a crucial problem. With a stereo pair of sensors, the 3D space can be discretized by an iso-disparity surface, and the depth reconstruction accuracy of the space is closely related to the iso-disparity curve positions. This paper presents a method to enable planning the position of these multiple stereo sensors in indoor environments. The proposed method is a mathematical geometry model, used to analyze the iso-disparity surface. We will show that the distribution of the iso-disparity surface and the depth reconstruction accuracy are controllable by the parameters of such model. This model can be used to dynamically adjust the positions, poses and baselines lengths of multiple stereo pairs of cameras in 3D space in order to get sufficient visibility and accuracy for surveillance tracking and 3D reconstruction. We implement the model and present uncertainty maps of depth reconstruction calculated while varying the baseline length, focal length, stereo convergence angle and sensor pixel length. The results of these experiments show how the depth reconstruction uncertainty depends on stereo pair’s baseline length, zooming and sensor physical properties.

  • 6. Emam, Seyed Mohammad
    et al.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khalili, Khalil
    Improving the Accuracy of Laser Scanning for 3D Model Reconstruction Using Dithering Technique2014In: Procedia Technology / [ed] Moldovan, L, Elsevier , 2014, Vol. 12Conference paper (Refereed)
    Abstract [en]

    Triangulation technique is one of the most commonly techniques used in three dimensional measurements. Depth reconstruction accuracy is a direct impact of the quantization process and this is related to the number of pixels of the sensor. Dithering technique (DT) benefits from relative fine movement between object and sensor to reduce the quantization error. This paper describes the theory of the DT and establishes a mathematical model. To evaluate if DT technique can improve the accuracy in real world, a control rig was designed and built, following which experiments were performed. The results showed that considerable improvement can be achieved in measurement accuracy.

  • 7. Hansson, H
    et al.
    Blomstrand, F
    Khatibi, Siamak
    Olsson, T
    Glutamate induced astroglial swelling1997In: On astrocytes and glutamate neurotransmission: New waves in brain information processing, Neuroscience Intelligence Unit, Springer, R.G. Landes Company , 1997, p. 106-120Chapter in book (Refereed)
  • 8. Jamshid, Homayoun
    et al.
    Lukaszewicz, Thomas
    Kashi, Amin
    Berghuvud, Ansel
    Zepernick, Hans-Jürgen
    Khatibi, Siamak
    Fusion of Digital Map Traffic Signs and Camera-detected Signs2011Conference paper (Refereed)
    Abstract [en]

    In this paper, we present several fusion approaches to merge speed limits reported in digital maps with detected speed limit signs using an onboard camera. Digital maps holding speed limits signs are required to be updated to cover speed limit changes and are unable to support variable speed limits. On the other hand, a camera system placed onboard a vehicular can detect variable speed limits as well as temporary speed limits at construction sites. However, an onboard camera cannot detect implicit speed limits. As such, a combination of digital map and camera system can provide more accurate speed limit information for driver assistance and support vehicle safety features. In this paper, the digital map and camera system are fused to obtain the desired more accurate speed limit information. The fused speed limits as well as those from the individual sources are compared with ground truth data obtained from an extensive measurement campaign spanning over 15000 km driving distance in five European countries. Specifically, five fusion approaches are defined, modeled and evaluated. Four of them are based on prioritizing information while the remaining approach is based on the classical Dempster-Shafer data fusion technique. The performance of the approaches are presented in terms of the percentage of correct speed limit detection with respect to the driving distance. The obtained results clearly show that fusion techniques can significantly increase the amount of correctly detected speed limits. A MATLAB based graphical user interface was designed to load test data, evaluate and present the results as fast and as efficient as possible.

  • 9. Kulesza, Wlodek
    et al.
    Chen, Jiandan
    Khatibi, Siamak
    Arrangement of a Multi Stereo Visual Sensor System for a Human Activities Space2008In: Stereo Vision / [ed] Bhatti, Asim, Vienna: InTech Education and Publishing , 2008, p. 152-172Chapter in book (Refereed)
    Abstract [en]

    The first part of this chapter introduces a mathematical geometry model which is used to analyze the iso-disparity surface. This model can be used to dynamically adjust the positions, poses and baseline lengths of multiple stereo pairs of cameras in 3D space in order to get sufficient visibility and accuracy for surveillance, tracking and 3D reconstruction. The depth reconstruction accuracy is quantitatively analyzed by the proposed model. The proposed iso-disparity mathematical model presents possibility of reliable control of the iso-disparity curves’ shapes and intervals by applying the systems configuration and target properties. In the second part of this chapter, the key factors affecting the accuracy of 3D reconstruction are analysed. It shows that the convergence angle and target distance influence the depth reconstruction accuracy most significantly. The depth accuracy constraints are implemented in the model to control the stereo pair’s baseline length, position and pose. It guarantees a certain accuracy in the 3D reconstruction. The reconstruction accuracy is verified by a cubic reconstruction method. The optimization is implemented by applying the camera, object and stereo pair constraints into the integer linear programming.

  • 10.
    Shahid, Muhammad
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Tuemay, Yared
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Popularity index through video semantic quality assessment2014Conference paper (Refereed)
    Abstract [en]

    Popularity of the streaming media content such as videos can be ascribed to the perceptual quality, to some extent, of the content. The traditional methods of audio/video quality assessment lack in provision of the input from higher cognitive of the human perception. Some studies have revealed that liking or disliking of a certain content can bias the human judgement towards video quality. In this paper, we have examined the impact of the use of semantic quality indicators namely audio content, audio quality, video content, and video quality in the assessment of quality of a video. Further, we have proposed a methodology to use these indicators for designing a prediction model for the popularity of streaming videos.

  • 11. Siddiqui, Rafid
    et al.
    Havaei, Mohammad
    Khatibi, Siamak
    Lindley, Craig
    PLASE: A novel planar surface extraction method for the autonomous navigation of micro-air vehicle2011Conference paper (Refereed)
    Abstract [en]

    A Planar Surface Extraction (PLASE) method is proposed for the indoor navigation of a micro-air vehicle (MAV). The algorithm finds planar clusters from the unorganized point clouds. This is achieved by implementing a novel approach that first segments the data points into clusters and then each cluster is estimated for its planarity. The method is tested on indoor point cloud data obtained by 3D PrimeSense based sensor. In order to validate the algorithm, a simulated model containing a set of planes has been constructed, with noise injected into the model. The results of the empirical evaluation suggest that the method performs well even in the presence of the noise and non-planar objects, suggesting that the method will be a viable one for use in MAV navigation in the presence of noisy sensor data.

  • 12.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, School of Computing.
    Havaei, Mohammad
    Siamak, Khatibi
    Blekinge Institute of Technology, School of Computing.
    Lindley, Craig
    Blekinge Institute of Technology, School of Computing.
    A novel plane extraction approach using supervised learning2013In: Machine Vision and Applications, ISSN 0932-8092, E-ISSN 1432-1769, Vol. 24, no 6, p. 1229-1237Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel approach for the classification of planar surfaces in an unorganized point clouds. A feature-based planner surface detection method is proposed which classifies a point cloud data into planar and non-planar points by learning a classification model from an example set of planes. The algorithm performs segmentation of the scene by applying a graph partitioning approach with improved representation of association among graph nodes. The planarity estimation of the points in a scene segment is then achieved by classifying input points as planar points which satisfy planarity constraint imposed by the learned model. The resultant planes have potential application in solving simultaneous localization and mapping problem for navigation of an unmanned-air vehicle. The proposed method is validated on real and synthetic scenes. The real data consist of five datasets recorded by capturing three-dimensional(3D) point clouds when a RGBD camera is moved in five different indoor scenes. A set of synthetic 3D scenes are constructed containing planar and non-planar structures. The synthetic data are contaminated with Gaussian and random structure noise. The results of the empirical evaluation on both the real and the simulated data suggest that the method provides a generalized solution for plane detection even in the presence of the noise and non-planar objects in the scene. Furthermore, a comparative study has been performed between multiple plane extraction methods.

  • 13.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Bio-inspired Metaheuristic based Visual Tracking and Ego-motion Estimation2014Conference paper (Refereed)
    Abstract [en]

    The problem of robust extraction of ego-motion from a sequence of images for an eye-in-hand camera configuration is addressed. A novel approach toward solving planar template based tracking is proposed which performs a non-linear image alignment and a planar similarity optimization to recover camera transformations from planar regions of a scene. The planar region tracking problem as a motion optimization problem is solved by maximizing the similarity among the planar regions of a scene. The optimization process employs an evolutionary metaheuristic approach in order to address the problem within a large non-linear search space. The proposed method is validated on image sequences with real as well as synthetic image datasets and found to be successful in recovering the ego-motion. A comparative analysis of the proposed method with various other state-of-art methods reveals that the algorithm succeeds in tracking the planar regions robustly and is comparable to the state-of-the art methods. Such an application of evolutionary metaheuristic in solving complex visual navigation problems can provide different perspective and could help in improving already available methods.

  • 14.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Robust Place Recognition with an Application to Semantic Topological Mapping2013Conference paper (Refereed)
    Abstract [en]

    The problem of robust and invariant representation of places is being addressed. A place recognition technique is proposed followed by an application to a semantic topological mapping. The proposed technique is evaluated on a robot localization database which consists of a large set of images taken under various weather conditions. The results show that the proposed method can robustly recognize the places and is invariant to geometric transformations, brightness changes and noise. The comparative analysis with the state-of-the-art semantic place description methods show that the method outperforms the competing methods and exhibits better average recognition rates.

  • 15.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Robust Visual Odometry Estimation of Road Vehicle from Dominant Surfaces for Large Scale Mapping2015In: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 9, no 3, p. 314-322Article in journal (Refereed)
    Abstract [en]

    Every urban environment contains a rich set of dominant surfaces which can provide a solid foundation for visual odometry estimation. In this work visual odometry is robustly estimated by computing the motion of camera mounted on a vehicle. The proposed method first identifies a planar region and dynamically estimates the plane parameters. The candidate region and estimated plane parameters are then tracked in the subsequent images and an incremental update of the visual odometry is obtained. The proposed method is evaluated on a navigation dataset of stereo images taken by a car mounted camera that is driven in a large urban environment. The consistency and resilience of the method has also been evaluated on an indoor robot dataset. The results suggest that the proposed visual odometry estimation can robustly recover the motion by tracking a dominant planar surface in the Manhattan environment. In addition to motion estimation solution a set of strategies are discussed for mitigating the problematic factors arising from the unpredictable nature of the environment. The analyses of the results as well as dynamic environmental strategies indicate a strong potential of the method for being part of an autonomous or semi-autonomous system.

  • 16.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, School of Computing.
    Khatibi, Siamak
    Blekinge Institute of Technology, School of Computing.
    Semantic indoor maps2013Conference paper (Refereed)
    Abstract [en]

    The cumbersome process of construction and incremental update of large indoor maps can be simplified by semantic maps. A novel semantic mapping method for indoor environments is proposed which employs a flash-n-extend strategy for constructing and updating the map. At the exposure of every flash event, a 3D snapshot of the environment is taken which is extended until flash event reoccurs. A flash event occurs at a motion state transition of a mobile robot which is detected by the decomposition of motion estimates. The proposed method is evaluated on a set of image sequences and is found to be robust in building indoor maps which are suitable for robust autonomous navigation. The constructed maps provide simplistic representation of the environment which makes it ideal for high-level reasoning tasks.

  • 17.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Semantic Urban Maps2014In: International Conference on Pattern Recognition, IEEE , 2014, p. 4050-4055Conference paper (Refereed)
    Abstract [en]

    A novel region based 3D semantic mapping method is proposed for urban scenes. The proposed Semantic Urban Maps (SUM) method labels the regions of segmented images into a set of geometric and semantic classes simultaneously by employing a Markov Random Field based classification framework. The pixels in the labeled images are back-projected into a set of 3D point-clouds using stereo disparity. The point-clouds are registered together by incorporating the motion estimation and a coherent semantic map representation is obtained. SUM is evaluated on five urban benchmark sequences and is demonstrated to be successful in retrieving both geometric as well as semantic labels. The comparison with relevant state-of-art method reveals that SUM is competitive and performs better than the competing method in average pixel-wise accuracy.

  • 18.
    Siddiqui, Rafid
    et al.
    Blekinge Institute of Technology, School of Computing.
    Khatibi, Siamak
    Blekinge Institute of Technology, School of Computing.
    Bitra, Sridhar
    Blekinge Institute of Technology, School of Computing.
    Tavassoli, Sam
    Blekinge Institute of Technology, School of Computing.
    Scene perception by context-aware dominant surfaces2013Conference paper (Refereed)
    Abstract [en]

    Most of the computer vision algorithms operate pixel-wise and process image in a small neighborhood for feature extraction. Such a feature extraction strategy ignores the context of an object in the real world. Taking geometric context into account while classifying various regions in a scene, we can discriminate the similar features obtained from different regions with respect to their context. A geometric context based scene decomposition method is proposed and is applied in a context-aware Augmented Reality (AR) system. The proposed system segments a single image of a scene into a set of semantic classes representing dominant surfaces in the scene. The classification method is evaluated on an urban driving sequence with labeled ground truths and found to be robust in classifying the scene regions into a set of dominant applicable surfaces. The classified dominant surfaces are used to generate a 3D scene. The generated 3D scene provides an input to the AR system. The visual experience of 3D scene through the contextually aware AR system provides a solution for visual touring from single images as well as an experimental tool for improving the understanding of human visual perception.

  • 19.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    A New Methodology for Evaluating Various Methods of 3D Reconstruction from Single Image2012In: Image and Signal Processing (CISP), 2012 5th International Congress on, IEEE, 2012, p. 582-586Conference paper (Refereed)
    Abstract [en]

    Consumer market is recently experiencing 3D display. To prepare the market for new era of 3D TV, the 3D display popularity can be increased by making ease of capturing or generating of stereo information. The results of recent research on 3D structure modeling from single images can be used to generate stereo images. We evaluate some of typical 3D reconstruction methods from single images in relation of using the results in 3D display. The evaluation is not only based on the experts' opinions and statistic test but also an objective methodology is introduced. Only planar surfaces, like as in any man made structure scenes, are used in the objective evaluation. The number of planes is varied in a controlled way. Three popular and classic methods are chosen for the evaluation with this new methodology. And the evaluation result is consistent with the statistical result of human inquiries.

  • 20.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    A Software Method to Extend Tonal Levels and Widen Tonal Range of CCD Sensor Images2015In: 2015 9TH INTERNATIONAL CONFERENCE ON SIGNAL PROCESSING AND COMMUNICATION SYSTEMS (ICSPCS), IEEE Communications Society, 2015Conference paper (Refereed)
    Abstract [en]

    As one of important outcomes of the past decades of researches on sensor arrays for digital cameras, the manufacturers of sensor array technology have responded to the necessity and importance of obtaining an optimal fill factor, which has great impact on collection of incident photons on the sensor, with hardware solution e.g. by introducing microlenses. However it is still impossible to make a fill factor of 100% due to the physical limitations in practical development and manufacturing of digital camera. This has been a bottle neck problem for improving dynamic range and tonal levels for digital cameras e.g. CCD cameras. In this paper we propose a software method to not only widen the recordable dynamic range of a captured image by a CCD camera but also extend its tonal levels. In the method we estimate the fill factor and by a resampling process a virtual fill factor of 100% is achieved where a CCD image is rearranged to a new grid of virtual subpixels. A statistical framework including local learning model and Bayesian inference is used for estimating new sub-pixel intensity values. The highest probability of sub-pixels intensity values in each resampled pixel area is used to estimate the pixel intensity values of the new image. The results show that in comparison to the methods of histogram equalization and image contrast enhancement, which are generally used for improving the displayable dynamic range on only one image, the tonal levels and dynamic range of the image is extended and widen significantly and respectively.

  • 21.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Back to basics: Towards novel computation and arrangement of spatial sensory in images2016In: Acta Polytechnica, ISSN 1210-2709, Vol. 56, no 5, p. 409-416Article in journal (Refereed)
    Abstract [en]

    The current camera has made a huge progress in the sensor resolution and the low-luminance performance. However, we are still far from having an optimal camera as powerful as our eye is. The study of the evolution process of our visual system indicates attention to two major issues: the form and the density of the sensor. High contrast and optimal sampling properties of our visual spatial arrangement are related directly to the densely hexagonal form. In this paper, we propose a novel software-based method to create images on a compact dense hexagonal grid, derived from a simulated square sensor array by a virtual increase of the fill factor and a half a pixel shifting. After that, the orbit functions are proposed for a hexagonal image processing. The results show it is possible to achieve image processing operations in the orbit domain and the generated hexagonal images are superior, in detection of curvature edges, to the square images. We believe that the orbit domain image processing has a great potential to be the standard processing for hexagonal images.

  • 22.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Novel Software-based Method to Widen Dynamic Range of CCD Sensor Images2015In: / [ed] Yu-Jin Zhang, Springer, 2015, Vol. 9218, p. 572-583Conference paper (Refereed)
    Abstract [en]

    In the past twenty years, CCD sensor has made huge progress in improving resolution and low-light performance by hardware. However due to physical limits of the sensor design and fabrication, fill factor has become the bottle neck for improving quantum efficiency of CCD sensor to widen dynamic range of images. In this paper we propose a novel software-based method to widen dynamic range, by virtual increase of fill factor achieved by a resampling process. The CCD images are rearranged to a new grid of virtual pixels com-posed by subpixels. A statistical framework consisting of local learning model and Bayesian inference is used to estimate new subpixel intensity. By knowing the different fill factors, CCD images were obtained. Then new resampled images were computed, and compared to the respective CCD and optical image. The results show that the proposed method is possible to widen significantly the recordable dynamic range of CCD images and increase fill factor to 100 % virtually.

  • 23.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    The impact of curviness on four different image sensor forms and structures2018In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, no 2, article id 429Article in journal (Refereed)
    Abstract [en]

    The arrangement and form of the image sensor have a fundamental effect on any further image processing operation and image visualization. In this paper, we present a software-based method to change the arrangement and form of pixel sensors that generate hexagonal pixel forms on a hexagonal grid. We evaluate four different image sensor forms and structures, including the proposed method. A set of 23 pairs of images; randomly chosen, from a database of 280 pairs of images are used in the evaluation. Each pair of images have the same semantic meaning and general appearance, the major difference between them being the sharp transitions in their contours. The curviness variation is estimated by effect of the first and second order gradient operations, Hessian matrix and critical points detection on the generated images; having different grid structures, different pixel forms and virtual increased of fill factor as three major properties of sensor characteristics. The results show that the grid structure and pixel form are the first and second most important properties. Several dissimilarity parameters are presented for curviness quantification in which using extremum point showed to achieve distinctive results. The results also show that the hexagonal image is the best image type for distinguishing the contours in the images. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

  • 24.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Towards Measuring of Depth Perception from Monocular Shadow Technique with Application in a Classical Painting2016In: Journal of Computers, ISSN 1796-203X, Vol. 11, p. 310-319Article in journal (Refereed)
    Abstract [en]

    Depth perception is one of important abilities of the human visual system to perceive the three dimensional world. Shadow technique that offers different depth information from different viewing points, known as Da Vinci stereopsis, has been used in classical paintings. In this paper, we report a method towards measuring the relative depth information stimulated by Da Vinci stereopsis in a classical painting. We set up a positioning array of cameras for capturing images from the portrait using a high resolution camera, where the changes of shadow areas are measured by featuring the effects as point and line changes. The result shows that 3D effects of the classical painting are not only a perceptual phenomenon but they are also physically tangible and can be measured. We confirm validity of the method by its implementation even on a typical single image and comparison of results between the single image and the portrait.

  • 25.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Creative Technologies. Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Virtual deformable image sensors: Towards to a general framework for image sensors with flexible grids and forms2018In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, no 6, article id 1856Article in journal (Refereed)
    Abstract [en]

    Our vision system has a combination of different sensor arrangements from hexagonal to elliptical ones. Inspired from this variation in type of arrangements we propose a general framework by which it becomes feasible to create virtual deformable sensor arrangements. In the framework for a certain sensor arrangement a configuration of three optional variables are used which includes the structure of arrangement, the pixel form and the gap factor. We show that the histogram of gradient orientations of a certain sensor arrangement has a specific distribution (called ANCHOR) which is obtained by using at least two generated images of the configuration. The results showed that ANCHORs change their patterns by the change of arrangement structure. In this relation pixel size changes have 10-fold more impact on ANCHORs than gap factor changes. A set of 23 images; randomly chosen from a database of 1805 images, are used in the evaluation where each image generates twenty-five different images based on the sensor configuration. The robustness of ANCHORs properties is verified by computing ANCHORs for totally 575 images with different sensor configurations. We believe by using the framework and ANCHOR it becomes feasible to plan a sensor arrangement in the relation to a specific application and its requirements where the sensor arrangement can be planed even as combination of different ANCHORs. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

  • 26.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Siamak, Khatibi
    Blekinge Institute of Technology, Faculty of Computing, Department of Technology and Aesthetics.
    Estimation of Image Sensor Fill Factor Using a Single Arbitrary Image2017In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 17, no 3, p. 620-Article in journal (Refereed)
    Abstract [en]

    Achieving a high fill factor is a bottleneck problem for capturing high-quality images. There are hardware and software solutions to overcome this problem. In the solutions, the fill factor is known. However, this is an industrial secrecy by most image sensor manufacturers due to its direct effect on the assessment of the sensor quality. In this paper, we propose a method to estimate the fill factor of a camera sensor from an arbitrary single image. The virtual response function of the imaging process and sensor irradiance are estimated from the generation of virtual images. Then the global intensity values of the virtual images are obtained, which are the result of fusing the virtual images into a single, high dynamic range radiance map. A non-linear function is inferred from the original and global intensity values of the virtual images. The fill factor is estimated by the conditional minimum of the inferred function. The method is verified using images of two datasets. The results show that our method estimates the fill factor correctly with significant stability and accuracy from one single arbitrary image according to the low standard deviation of the estimated fill factors from each of images and for each camera.

  • 27.
    Zepernick, Hans-Jürgen
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Iqbal, Muhammad Imran
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Quality of Experience of Digital Multimedia Broadcasting Services: An Experimental Study2016In: 2016 IEEE Sixth International Conference on Communications and Electronics (ICCE), IEEE, 2016, p. 437-442Conference paper (Refereed)
    Abstract [en]

    Digital multimedia broadcasting (DMB), also know as mobile TV, has been developed as a digital radio transmission technology that supports multimedia services such as TV, radio and datacasting. Especially, the terrestrial version of DMB, referred to as T-DMB, has been widely deployed in South Korea to deliver multimedia services to mobile devices ranging from smartphones to laptops, car navigation systems, and telematic devices for automotives. Although T-DMB is claimed to theoretically work without difficulties in vehicles with speeds up to 300 km/h, in practice, occasional skips and other temporal and spatial artifacts have been observed. In this paper, we provide an experimental study of the Quality of Experience (QoE) of T-DMB with focus on TV services. The study is based on a measurement campaign that was conducted in a live T-DMB system in South Korea consisting of TV broadcasters and DMB receivers in vehicles. In particular, a comprehensive subjective test has been conducted on the DMB test material that was obtained in the measurement campaign. A statistical analysis of the user ratings obtained from the subjective tests is reported to quantify the QoE of T-DMB in terms of mean opinion scores (MOSs) and higher order statistics. The obtained results may be used to develop related QoE models for this type of systems and services. In particular, the results may suggest to exploit insights obtained from higher order statistics such as skewness and kurtosis into QoE modeling rather than considering only MOS and variance.

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