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Reducing the optimisation effort in batch mosaicing

AIP Conference Proceedings 2012年第1期1479卷

作者： Armagan Elibol Nuno Gracia Rafael Garcia Dept. of Mathematical Engineering Yildiz Technical University Istanbul Turkey Computer Vision and Robotics Group University of Girona Girona Spain

Image mosaicing methods have become very popular thanks to the rapid progress in obtaining optical data using robotic platforms. Global alignment which is known as finding best image registration parameters taking into account overlapping image pairs is one of the essential steps of image mosaicing process in order to obtain seamless mosaics. Global alignment usually employs non-linear optimisation methods to minimise the error metric defined over correspondences detected between overlapping image pairs. In this paper, we propose a method that uses graph theory principles to reduce the total number of overlapping image pairs used in the global alignment process without disturbing the final mosaic quality. This reduction allows for obtaining image mosaics with reduced computational cost and time. The method is validated through two experiments which involve challenging underwater datasets.

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Joint Probability of Shape and Image Similarities to Retrieve 2D TRUS-MR Slice Correspondence for Prostate Biopsy

Joint Probability of Shape and Image Similarities to Retriev...

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society

作者： J. Mitra S. Ghose D. Sidibé R. Martí A. Oliver X. Lladó J. C. Vilanova J. Comet F. Meriaudeau Le2i CNRS-UMR 6306 Université de Bourgogne Le Creusot France Le2i CNRS-UMR 6306 Université de Bourgogne Le Creusot France. the Computer Vision and Robotics Group University of Girona Girona Spain. the Girona Magnetic Resonance Center Girona Spain. the Hospital Dr. Josep Trueta Girona Spain.

ISBN: (纸本)9781424441198

This paper presents a novel method to identify the 2D axial Magnetic Resonance (MR) slice from a pre-acquired MR prostate volume that closely corresponds to the 2D axial Transrectal Ultrasound (TRUS) slice obtained during prostate biopsy. The method combines both shape and image intensity information. The segmented prostate contours in both the imaging modalities are described by shape-context representations and matched using the Chi-square distance. Normalized mutual information and correlation coefficient between the TRUS and MR slices are computed to find image similarities. Finally, the joint probability values comprising shape and image similarities are used in a rule-based framework to provide the MR slice that closely resembles the TRUS slice acquired during the biopsy procedure. The method is evaluated for 20 patient datasets, of which 18 results match at least one of the two clinical expert choices.

关键词： Joint Probability TRUS-MR Slice Correspondence TRUS

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Surface reconstruction methods for the recovery of 3D models from underwater interest areas

Surface reconstruction methods for the recovery of 3D models...

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OCEANS - Europe

作者： Ricard Campos Rafael Garcia Tudor Nicosevici Computer Vision and Robotics Group University of Girona Spain

3D models of seafloor interest areas having a strong 3D relief are a rich source of information for scientists. In the recent years, the computer vision community has been developing techniques to achieve the discrete reconstruction of these interest areas from a set of images. However, 3D reconstruction methods output a 3D point cloud as a representation of the shape of the observed object/area. This representation lacks connectivity information, and a surface that describes the underlying object is needed for both performing computations on the object and to achieve its correct visualization. In this article we aim to survey the State-of-the-Art of the problem of reconstructing the surface of an object represented by a cloud of points. This set of points is assumed to be the result of a computer vision based 3D reconstruction pipeline.

关键词： Three dimensional displays Surface reconstruction Surface treatment Image reconstruction computer vision Pipelines Cameras

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Attracting talent to increase interest for engineering among secondary school students

Attracting talent to increase interest for engineering among...

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IEEE Education Engineering (EDUCON)

作者： Miquel Villanueva Xevi Cufí Andrés ElFakdi Pere Ridao Rafael Garcia Computer Vision and Robotics Group University of Girona Girona Spain

This paper reports our experience in developing a team-based project activity to promote engineering programs among secondary school students. The aim of the activity is to increase the interest of students for science and technology in general, but also to promote engineering skills, capabilities and values, leading to attract more secondary school students to enrollment for engineering programs. Simple theoretical concepts are illustrated through hands-on experimentation. To achieve this goal, the students build a Remotely Operated Underwater Robot in a 2½-day workshop. The robot is built using low-cost materials and the students customize their own design over the different phases of the workshop. Once the activity is completed, every team understands that with teamwork, effort and a good working strategy, every problem can be overcome. At the end of the activity, a survey is conducted through an assessment survey questionnaire which reflects different aspects related with the development of the activity and the degree to which learning of its different facets has been achieved. The responses and feedback from students serve not only to evaluate the workshop, but also as feedback for future fine-tuning of the different phases as pedagogical learning tools.

关键词： Robots Conferences DC motors Educational institutions Vehicles Engineering education Wires

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Detection of interest points in turbid underwater images

Detection of interest points in turbid underwater images

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OCEANS - Europe

作者： Rafael Garcia Nuno Gracias Computer Vision and Robotics Group University of Girona Girona Spain

Our research is motivated by an evident lack of evaluation of recent image matching techniques for applications in underwater vision. This paper is a first step in this direction. This work compares the performance of popular salient keypoint detectors on images degraded by turbidity. We show that, as opposed to over-land, on images acquired in water medium, Hessian-based approaches outperform their Laplacian and Harris counterparts. Fast Hessian, the detector of the Speeded Up Robust Features (SURF) matching technique, is recognized to be the best method for scale-invariant detection. Conversely, when invariance to scale is not required, a combination of standard Hessian and Harris with sub-pixel accuracy and non-maxima suppression is more accurate. The objective of our work was also to create and distribute a reference set of turbid images, which can be used to evaluate processing, detection, description and matching techniques for underwater applications. We present a collection of 36 images acquired by a specially designed trinocular system under 12 gradually increasing turbidity levels. We also draw attention to image quality assessment method called SSIM, Structural SIMilarity index, which reliably quantifyes degradation of image quality caused by turbidity. As a whole, the major goal of this paper is to provide an updated reference for researchers dealing with keypoint detection in underwater imaging.

关键词： Detectors Cameras Scattering Visualization Laplace equations Accuracy Dairy products

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Supervised texture segmentation through a multi-level pixel-based classifier based on specifically designed filters

Supervised texture segmentation through a multi-level pixel-...

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IEEE International Conference on Image Processing

作者： Jaime Melendez Xavier Girones Domenec Puig Intelligent Robotics and Computer Vision Group Department of Computer Science and Mathematics Rovira i Virgili University Spain

This paper presents a new, efficient technique for supervised texture segmentation based on a set of specifically designed filters and a multi-level pixel-based classifier. Filter design is carried out by means of a neural network, which is trained to maximize the filters' discrimination power among the texture classes under consideration. Texture features obtained with these filters are then processed by a classification scheme that utilizes multiple evaluation window sizes following a top-down approach, which iteratively refines the resulting segmentation. The proposed technique is compared to previous supervised texture segmenters by using both synthetic compositions and real outdoor textured images.

关键词： Filter banks Image segmentation Feature extraction Gabor filters Adaptive filters Conferences Support vector machines

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A non-linear diffeomorphic framework for prostate multimodal registration

A non-linear diffeomorphic framework for prostate multimodal...

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2011 International Conference on Digital Image Computing: Techniques and Applications, DICTA 2011

作者： Mitra, Jhimli Kato, Zoltan Martí, Robert Oliver, Arnau Lladó, Xavier Ghose, Soumya Vilanova, Joan C. Meriaudeau, Fabrice Le2i-UMR CNRS 5158 Université de Bourgogne Le Creusot France Computer Vision and Robotics Group Universitat de Girona Girona Spain Department of Image Processing and Computer Graphics University of Szeged Szeged Hungary Girona Magnetic Resonance Center Girona Spain

ISBN: (纸本)9780769545882

This paper presents a novel method for non-rigid registration of prostate multimodal images based on a nonlinear framework. The parametric estimation of the non-linear diffeomorphism between the 2D fixed and moving images has its basis in solving a set of non-linear equations of thin-plate splines. The regularized bending energy of the thin-plate splines along with the localization error of established correspondences is jointly minimized with the fixed and transformed image difference, where, the transformed image is represented by the set of non-linear equations defined over the moving image. The traditional thin-plate splines with established correspondences may provide good registration of the anatomical targets inside the prostate but may fail to provide improved contour registration. On the contrary, the proposed framework maintains the accuracy of registration in terms of overlap due to the non-linear thinplate spline functions while also producing smooth deformations of the anatomical structures inside the prostate as a result of established corrspondences. The registration accuracies of the proposed method are evaluated in 20 pairs of prostate midgland ultrasound and magnetic resonance images in terms of Dice similarity coefficient with an average of 0.982 ± 0.004, average 95% Hausdorff distance of 1.54 ± 0.46 mm and mean target registration and target localization errors of 1.90±1.27 mm and 0.15 ± 0.12 mm respectively. © 2011 IEEE.

关键词： Ultrasonics

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An adaptable vision system for the automatic inspection of surface defects in automotive headlamp lenses

An adaptable vision system for the automatic inspection of s...

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IEEE International Conference on Automation Science and Engineering (CASE)

作者： S. Satorres Martínez J. Gómez Ortega A. Sánchez García J. Gámez García Corresponding author is with the Group of Robotics Automation and Computer Vision University of Jaen Spain Universidad de Jaen Jaen JaÃ©n ES

As a great part of the industrial inspection problems require specific, expensive, and highly complex solutions, there is the need to build flexible systems capable to be easily adapted to different models of a part. In this context, this paper proposes the use of a component-based methodology for designing and building flexible inspection systems for automotive headlamp lenses. Through computer vision, and taking into account the different elements that can be utilized in an industrial environment, we propose the use of a component based architecture for easily designing and building industrial inspection systems for this kind of parts. Within this architecture, each software, or hardware element, is encapsulated in a component with a predefined input/ouput layout and, later, it can be used considering the task inspection requirements. The main advantages of the proposed working philosophy are its flexibility, that the resulting machine vision can be easily adapted to any kind of headlamp lens, and that it is fully open to any new component (lighting system, process algorithm, industrial conveyor, etc.). This proposition has been successfully validated building an industrial prototype that was tested in both, the lab, and in a production line.

关键词： Inspection Lenses Lighting Cameras Machine vision Software Hardware

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Statistical shape and probability prior model for automatic prostate segmentation

Statistical shape and probability prior model for automatic ...

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2011 International Conference on Digital Image Computing: Techniques and Applications, DICTA 2011

作者： Ghose, Soumya Oliver, Arnau Martí, Robert Lladó, Xavier Freixenet, Jordi Mitra, Jhimli Vilanova, Joan C. Comet, Josep Meriaudeau, Fabrice Le2i-UMR CNRS 5158 Université de Bourgogne Le Creusot France Computer Vision and Robotics Group Universitat de Girona Girona Spain Girona Magnetic Resonance Center Girona Spain University Hospital Dr. Josep Trueta Girona Spain

ISBN: (纸本)9780769545882

Accurate prostate segmentation in Trans Rectal Ultra Sound (TRUS) images is an important step in different clinical applications. However, the development of computer aided automatic prostate segmentation in TRUS images is a challenging task due to low contrast, heterogeneous intensity distribution inside the prostate region, imaging artifacts like shadow, and speckle. Significant variations in prostate shape, size and contrast between the datasets pose further challenges to achieve an accurate segmentation. In this paper we propose to use graph cuts in a Bayesian framework for automatic initialization and propagate multiple mean parametric models derived from principal component analysis of shape and posterior probability information of the prostate region to segment the prostate. The proposed framework achieves a mean Dice similarity coefficient value of 0.974±0.006, mean mean absolute distance value of 0.49±0.20 mm and mean Hausdorff distance of 1.24±0.56 mm when validated with 23 datasets in a leave-one-patient-out validation framework. © 2011 IEEE.

关键词： Principal component analysis

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An accurate 3D feature tracking system with wide-baseline stereo smart cameras

An accurate 3D feature tracking system with wide-baseline st...

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ACM/IEEE International Conference on Distributed Smart Cameras, ICDSC

作者： Dominik Rueß Kristian Manthey Ralf Reulke German AeroSpace Center Optical Information Systems Institute of Robotics and Mechatronics Berlin Germany Department of Computer Science Research and Lecture Group Computer Vision Humboldt-Universität zu Berlin Berlin Germany

A typical video surveillance system consists of at least one camera, controlled by an operator. To decrease the human error rate and to generally lessen the burden of operators, many object tracking systems have been implemented, most of which work in 2D image space. If used centralized, this is a very expensive task. Furthermore, if several views are to be fused, large inaccuracies arise due to ground plane assumptions, for instance. Lastly, in outdoor setups, quite often there is a need for slower channels like Wireless LAN which cannot cope with the full resolution data stream. We provide a smart camera system which performs the intensive tasks like background estimation or feature extraction. A central unit only has to process the received data in feature space, increasing scalability. Additionally, the object tracking problem is converted to an accurate 3D feature tracking, avoiding difficulties such as proper object segmentation and adding increased trajectory accuracy. The feature regions are computed within the smart camera. A wide-baseline feature matching approach has been employed to allow more freedom in the placement of the single smart cameras.

关键词： Trajectory Three dimensional displays Cameras Smart cameras Estimation Image reconstruction Feature extraction

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