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22nd brazilian symposium on computer graphics and image processing

作者： Dorini, Leyza Baldo Leite, Neucimar Jeronimo UTFPR Fed Univ Technol Parana Dept Informat Curitiba Parana Brazil Univ Estadual Campinas Inst Comp Campinas Brazil

ISBN: (纸本)9781424449798

Multiscale approaches have been largely considered in several signal processing applications. They play an important role when designing automatic methods to cope with real world measurements where, in most of the cases, there is no prior information about which would be the appropriate scale. The basic idea behind a multiscale analysis is to embed the original signal into a family of derived signals, thus allowing the analysis of different representation levels and, further, the choice of the ones exhibiting the interest features. This paper presents a brief survey of two broadly used multiscale formulations, namely, wavelets and scale-space filtering. We present the basic definitions and some possible applications of these approaches in image processing.

关键词： multiscale image analysis wavelets scale-space filtering mathematical morphology

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Detecting Buildings in Historical Photographs Using Bag-of-Keypoints

Detecting Buildings in Historical Photographs Using Bag-of-K...

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22nd brazilian symposium on computer graphics and image processing

作者： Batista, Natalia C. Lopes, Ana Paula B. Araujo, Arnaldo de A. Fed Univ Minas Gerais UFMG Dept Comp Sci BR-31270010 Belo Horizonte MG Brazil

ISBN: (纸本)9781424449781

The strategies for the preservation of historical documents can include their digitization, which is an effective way to make them publicly available while preventing degradation of the original sources. The Arquivo Public Mineiro (APM), the Archives of the State of Minas Gerais, has a collection of historical photographs from Brazil, and some of them have been digitized. The availability of digital copies of historical photographs makes it possible to apply Content-Based image Retrieval (CBIR) techniques to alleviate the huge manual effort that is put nowadays into their description and indexing. On the other side, such images are usually more challenging than modern photographs, because of the poor quality of the originals and several degradation effects. In this work, it is proposed a technique based on a bag-of-keypoints representation to identify images containing buildings in the APM photographic collection. The bag-of-keypoints is an efficient image representation technique, which has been proved robust to occlusion and variations due to pose, scale, illumination and several transformations. Experiments were performed on the images from the APM collection, to classify them between building and non-building, using bag-of-keypoints representations of those images. Results show that, despite of the poor quality of the images, the bag-of-keypoints representation is able to provide good detection rates, indicating the suitability of the proposed method for the task.

关键词： Historical photographs image classification Buildings recognition Bag-of-keypoints

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Stereo Based Structure Recovery of Underwater Scenes from Automatically Restored images

Stereo Based Structure Recovery of Underwater Scenes from Au...

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22nd brazilian symposium on computer graphics and image processing

作者： Nascimento, Erickson Campos, Mario Barros, Wagner Univ Fed Minas Gerais Dept Ciencia Comp Belo Horizonte MG Brazil

ISBN: (纸本)9781424449781

In this paper we present a fully automatic methodology for underwater image restoration which is based on classical physical models of light propagation in participating media. The technique uses pairs of images acquired from distinct viewpoints under the same environmental conditions. At the kernel of the method is an iterative algorithm that is based on a contrast metric that automatically estimates all parameters of the model with good accuracy at a significantly low computational cost. We then present an algorithm that uses the model with the estimated parameters to improve the quality of images of underwater scenes taken under natural illumination, (i.e. without any special light source). First we show the quality of parameters estimated by our approach by comparing against the same parameters obtained manually like in other works in the literature. Once better estimated parameters greatly influence the quality of restored images, we performed experiments with images taken from both synthesized and real scenes to verify the performance of the proposed method. Two main aspects were considered: image quality and quality of disparity maps produced by a standard stereo algorithm. image quality was assessed by a quantitative measure of contrast, which is typically used in related literature. We also compare the results obtained by our methodology with those obtained with classic image enhancement tools. The results obtained with our methodology demonstrate improvement both in scene contrast of recovered underwater images and in the accuracy of the disparity maps under different water turbidity levels.

关键词： underwater physics based vision stereo image restoration visibility scattering attenuation

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Digital image processing in Remote Sensing

Digital Image Processing in Remote Sensing

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22nd brazilian symposium on computer graphics and image processing

作者： Fonseca, Leila M. G. Namikawa, Laercio M. Castejon, Emiliano F. Natl Inst Space Res INPE Image Proc Div BR-12227010 Sao Jose Dos Campos SP Brazil

ISBN: (纸本)9781424449798

Imaging systems, particularly those on board satellites, provide a repetitive and consistent view of the earth that has been used in many remote sensing applications such as urban growth, deforestation and crop monitoring, weather prediction, land use mapping, land cover mapping and so on. For each application it is necessary to develop a specific methodology to extract information from the image data. To develop a methodology it is necessary to identify a procedure based on image processing techniques that is more adequate to the problem solution. In spite of the application complexity, some basic techniques are common in most of the remote sensing applications named as image registration, image fusion, image segmentation and classification. Hence, this paper aims to present an overview about the use of image processing techniques to solve a general problem on remote sensing application. A case study on an urban application is provided to illustrate the use of remote sensing technologies for solving the problem.

关键词： image processing remote sensing open source software satellite images

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Extraction and compression of hierarchical isocontours from image data

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computerIZED MEDICAL IMAGING And graphics 2006年第4期30卷 231-242页

作者： Lewiner, Thomas Lopes, Helio Velho, Luiz Mello, Vinicius PUC Dept Math Rio De Janeiro Brazil INRIA Geometr Project Sophia Antipolis France IMPA Visgraf Project Rio De Janeiro Brazil

In this work, we introduce a new scheme to extract hierarchical isocontours from regular and irregular 2D sampled data and to encode it at single rate or progressively. A dynamic tessellation is used to represent and adapt the 2D data to the isocontour. This adaptation induces a controlled multi-resolution representation of the isocontour. This representation can then be encoded while controlling the geometry and topology of the decoded isocontour. The resulting algorithms form an efficient and flexible isocontour extraction and compression scheme. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： level sets data compression simplicial methods progressive transmission geometry processing

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Adaptive deformable models

Adaptive deformable models

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17th brazilian symposium on computer graphics and image processing/2nd Ibero-American symposium on computer graphics

作者： Goldenstein, S Vogler, C Velho, L Univ Estadual Campinas BR-13083971 Campinas SP Brazil

ISBN: (纸本)0769522270

Deformable models are a powerful tool in both computer graphics and computer vision. The description and implementation of the deformations have to be simultaneously flexible and powerful, otherwise the technique may not satisfy the requirements of all the distinct applications. In this paper we introduce a new method for deformable model specification: deformable fields. Deformable fields are conceptually simple, lead to an easy implementation, and are suitable for adaptive models. We apply our new technique to describe an adaptive deformable face, and compare three different adaptation strategies. Additionally, we show how our technique is suitable to describe different individuals.

关键词： computer graphics

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Software shaders in interactive environments using relief impostors

Software shaders in interactive environments using relief im...

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17th brazilian symposium on computer graphics and image processing/2nd Ibero-American symposium on computer graphics

作者： Clua, EWG Feijó, B Dreux, M Fonseca, F ICAD/IGames/VisionLab Department of Computer Science PUC-Rio Brazil Department of Mechanical Engineering PUC-Rio Brazil

ISBN: (纸本)0769522270

This work presents an architecture for real-time visualization, which is able to render a set of 3D objects by using the CPU idle time. The objects being rendered are sent to the graphics pipeline as relief impostors. Their depth maps are used to apply 3D image-warping operations in order to prolong the life cycle of the synthesized images. While an image is within the graphics pipeline the CPU idle time is used to generate additional necessary images. With this method, it is possible to render images with special illumination models and effects that are impossible or unsuitable to be implemented with the shaders of the available graphics cards.

关键词： computer science

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Fast polygonization of variational implicit surfaces

Fast polygonization of variational implicit surfaces

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17th brazilian symposium on computer graphics and image processing/2nd Ibero-American symposium on computer graphics

作者： Cuno, A Esperança, C Oliveira, A Cavalcanti, PR Univ Fed Rio de Janeiro COPPE BR-21941 Rio De Janeiro Brazil

ISBN: (纸本)0769522270

This article presents a simple hierarchical adaptation of the Marching Cubes algorithm for polygonizing variational implicit surfaces used in modelling and reconstruction applications. The technique relies on placing the normal and boundary constraint points respecting a pseudo-Euclidean distance metrics. This procedure makes it possible to quickly prune the space and minimize the number of costly function evaluations and thus converge rapidly to the surface. Timings show that this technique tends to perform faster than Bloomenthal's continuation polygonizer [5].

关键词： computer graphics

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Data-based motion simulation through a Green's function approach

Data-based motion simulation through a Green's function appr...

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17th brazilian symposium on computer graphics and image processing/2nd Ibero-American symposium on computer graphics

作者： Ferreira, PE Torreao, JRA Carvalho, PCP IMPA Inst Nacl Matemat Pura & Aplicada Lab Visgraf BR-22460320 Rio De Janeiro Brazil

ISBN: (纸本)0769522270

We describe a data-driven motion simulation algorithm based on an affine image-matching equation. Solving such equation via the Green's function approach, we have obtained a pair of filters which, when applied over an input image, allow the generation of virtual sequences that convey a compelling motion impression. Complex rigid and nonrigid motions have been simulated this way, such as those of a pulsating heart, a twig in the wind and a levitating ball.

关键词： computer vision

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A load-balancing strategy for sort-first distributed rendering

A load-balancing strategy for sort-first distributed renderi...

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17th brazilian symposium on computer graphics and image processing/2nd Ibero-American symposium on computer graphics

作者： Abraham, F Celes, W Cerqueira, R Campos, JL Pontificia Univ Catolica Rio de Janeiro Dept Comp Sci Tecgraf BR-22450900 Rio de Janeiro RJ Brazil

ISBN: (纸本)0769522270

In this paper, we present a multi-threaded sort-first distributed rendering system. In order to achieve load balance among the rendering nodes, we propose a new partitioning scheme based on the rendering time of the previous frame. The proposed load-balancing algorithm is very simple to be implemented and works well for both geometry and rasterization-bound models. We also propose a strategy to assign tiles to rendering nodes that effectively uses the available graphics resources, thus improving rendering performance.

关键词： computer graphics

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