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XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)最新文献

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Performance Analysis of Oriented Feature Detectors 面向特征检测器的性能分析
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.38
F. Ayres, R. Rangayyan
Oriented feature detectors are fundamental tools in image understanding, as many images display relevant information in the form of oriented features. Several oriented feature detectors have been developed; some of the important families of oriented feature detectors are steerable filters and Gabor filters. In this work, a performance analysis is presented of the following oriented feature detectors: the Gaussian second-derivative steerable filter, the quadrature-pair Gaussian second-derivative steerable filter, the real Gabor filter, the complex Gabor filter, and a line operator that has been shown to outperform the Gaussian second-derivative steerable filter in the detection of linear structures in mammograms. The detectors are assessed in terms of their capability to detect the presence of oriented features, as well as their accuracy in the estimation of the angle of the oriented features present in the image. It is shown that the Gabor filters yield the best detection performance and angular accuracy, whereas the steerable filters have the best performance in terms of computational speed.
面向特征检测器是图像理解的基本工具,因为许多图像以面向特征的形式显示相关信息。几种定向特征检测器已经被开发出来;一些重要的定向特征检测器家族是可导向滤波器和Gabor滤波器。在这项工作中,提出了以下定向特征检测器的性能分析:高斯二阶导数可导向滤波器,正交对高斯二阶导数可导向滤波器,实Gabor滤波器,复Gabor滤波器,以及在乳房x光片线性结构检测中表现优于高斯二阶导数可导向滤波器的线算子。根据检测器检测定向特征的存在的能力以及它们在估计图像中存在的定向特征的角度方面的准确性来评估检测器。结果表明,Gabor滤波器具有最佳的检测性能和角精度,而可转向滤波器在计算速度方面具有最佳性能。
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引用次数: 23
Quadtree-Based Inexact Graph Matching for Image Analysis 基于四叉树的非精确图匹配图像分析
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.41
Luís Augusto Consularo, R. M. C. Junior
This paper presents a new method for segmentation and recognition of image objects based on structural pattern recognition. The input image is decomposed into regions through a quadtree algorithm. The decomposed image is represented by an attributed relational graph (ARG) named input graph. The objects to be recognized are also stored in an ARG named model graph. Object segmentation and recognition are accomplished by matching the input graph to the model graph. The possible inexact matches between the two graphs are cliques of the association graph between them. An objective function, to be optimized, is defined for each clique in order to measure how suitable is the match between the graphs. Therefore, recognition is modeled as an optimization procedure. A beam-search algorithm is used to optimize the objective function. Experimental results corroborating the proposed approach are presented.
提出了一种基于结构模式识别的图像目标分割与识别新方法。通过四叉树算法对输入图像进行区域分解。分解后的图像由一个命名为输入图(input graph)的属性关系图(ARG)表示。要识别的对象也存储在一个名为模型图的ARG中。通过将输入图与模型图进行匹配,实现对目标的分割和识别。两个图之间可能的不精确匹配是它们之间关联图的团。为每个团定义一个待优化的目标函数,以衡量图之间匹配的合适程度。因此,识别被建模为一个优化过程。采用波束搜索算法对目标函数进行优化。实验结果证实了所提出的方法。
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引用次数: 8
GEncode: Geometry-Driven Compression in Arbitrary Dimension and Co-Dimension GEncode:任意维和协维的几何驱动压缩
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.27
T. Lewiner, M. Craizer, H. Lopes, S. Pesco, L. Velho, Esdras Medeiros
Among the mesh compression algorithms, different schemes compress better specific categories of model. In particular, geometry-driven approaches have shown outstanding performances on isosurfaces. It would be expected these algorithm to also encode well meshes reconstructed from the geometry, or optimized by a geometric re-meshing. GEncode is a new single-rate compression scheme that compresses the connectivity of these meshes at almost zero-cost. It improves existing geometry-driven schemes for general meshes on both geometry and connectivity compression. This scheme extends naturally to meshes of arbitrary dimensions in arbitrary ambient space, and deals gracefully with non-manifold meshes. Compression results for surfaces are competitive with existing schemes.
在网格压缩算法中,不同的方案能更好地压缩特定类别的模型。特别是几何驱动方法在等值面上表现出了优异的性能。期望这些算法也能编码由几何重构的网格,或通过几何重网格优化。GEncode是一种新的单速率压缩方案,它几乎以零成本压缩这些网格的连通性。它在几何压缩和连通性压缩两方面改进了现有的一般网格几何驱动方案。该方案自然地扩展到任意环境空间中任意维的网格,并优雅地处理非流形网格。表面压缩结果与现有方案具有竞争力。
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引用次数: 11
Single-Image Shape from Defocus 从散焦单图像形状
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.47
J. Torreão, João L. Fernandes
The limited depth of field causes scene points at various distances from a camera to be imaged with different amounts of defocus. If images captured under different aperture settings are available, the defocus measure can be estimated and used for 3D scene reconstruction. Usually, defocusing is modeled by gaussian convolution over local image patches, but the estimation of a defocus measure based on that is hampered by the spurious high-frequencies introduced by windowing. Here we show that this can be ameliorated by the use of unnormalized gaussians, which allow defocus estimation from the zero-frequency Fourier component of the image patches, thus avoiding spurious high frequencies. As our main contribution, we also show that the modified shape from defocus approach can be extended to shape estimation from single shading inputs. This is done by simulating an aperture change, via gaussian convolution, in order to generate the second image required for defocus estimation. As proven here, the gaussian-blurred image carries an explicit depth-dependent blur component - which is missing from an ideal shading input -, and thus allows depth estimation as in the multi-image case.
有限的景深导致距离相机不同距离的场景点被成像时具有不同程度的散焦。如果在不同光圈设置下捕获的图像可用,则可以估计离焦度量并用于3D场景重建。通常,散焦是通过对局部图像块的高斯卷积来建模的,但是基于高斯卷积的散焦度量估计受到加窗引入的伪高频的阻碍。在这里,我们表明这可以通过使用非归一化高斯来改善,它允许从图像补丁的零频率傅立叶分量中进行散焦估计,从而避免虚假的高频。作为我们的主要贡献,我们还表明,改进的离焦形状方法可以扩展到从单个阴影输入的形状估计。这是通过模拟孔径变化来完成的,通过高斯卷积,以生成离焦估计所需的第二张图像。正如这里所证明的那样,高斯模糊图像带有一个明确的深度依赖的模糊分量——这在理想的阴影输入中是缺失的——因此可以像在多图像情况下一样进行深度估计。
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引用次数: 9
True Factor Analysis in Medical Imaging: Dealing with High-Dimensional Spaces 医学影像中的真因子分析:处理高维空间
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.50
A. Machado
This article presents a new method for discovering hidden patterns in high-dimensional dataset resulting from image registration. It is based on true factor analysis, a statistical model that aims to find clusters of correlated variables. Applied to medical imaging, factor analysis can potentially identify regions that have anatomic significance and lend insight to knowledge discovery and morphometric investigations related to pathologies. Existent factor analytic methods require the computation of the sample covariance matrix and are thus limited to low-dimensional variable spaces. The proposed algorithm is able to compute the coefficients of the model without the need of the covariance matrix, expanding its spectrum of applications. The method’s efficiency and effectiveness is demonstrated in a study of volumetric variability related to the Alzheimer’s disease.
本文提出了一种从图像配准产生的高维数据集中发现隐藏模式的新方法。它基于真因子分析,这是一种旨在找到相关变量簇的统计模型。应用于医学成像,因子分析可以潜在地识别具有解剖意义的区域,并为与病理相关的知识发现和形态测量调查提供见解。现有的因子分析方法需要计算样本协方差矩阵,因而局限于低维变量空间。该算法无需协方差矩阵即可计算模型的系数,扩大了算法的应用范围。该方法的效率和有效性在与阿尔茨海默病相关的体积变异性研究中得到了证明。
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引用次数: 0
Reconstruction-Diffusion: An Improved Maximum Entropy Reconstruction Algorithm Based on the Robust Anisotropic Diffusion 重建-扩散:一种改进的基于鲁棒各向异性扩散的最大熵重建算法
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.42
H. I. A. Bustos, H. Y. Kim
Maximum entropy (MENT) is a well-known image reconstruction algorithm. If only a small amount of acquisition data is available, this algorithm converges to a noisy and blurry image. We propose an improvement to this algorithm that consists on applying alternately the MENT reconstruction and the robust anisotropic diffusion (RAD). We have tested this idea for the reconstruction from full-angle parallel acquisition data, but the idea can be applied to any data acquisition scenario. The new technique has yielded surprisingly clear images with sharp edges even using extremely small amount of projection data.
最大熵(Maximum entropy, MENT)是一种著名的图像重建算法。当采集数据较少时,该算法会收敛到有噪声和模糊的图像。我们提出了一种改进算法,即交替应用MENT重建和鲁棒各向异性扩散(RAD)。我们已经在全角度平行采集数据的重建中测试了这个想法,但这个想法可以应用于任何数据采集场景。这项新技术即使使用极少量的投影数据,也能产生令人惊讶的清晰图像。
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引用次数: 2
Reduction of Interband Correlation for Landsat Image Compression 陆地卫星图像压缩中的带间相关性降低
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.43
D. Acevedo, Ana M. C. Ruedin
We present a lossless compressor for multispectral images that exploits interband correlations. Each band is divided into blocks, to which a wavelet transform is applied. The wavelet coefficients are predicted by means of a linear combination of coefficients belonging to the same orientation and spatial location. The prediction errors are then encoded with an entropy - based coder. Our original contributions are i) the inclusion, among the candidates for prediction, of coefficients of the same location from other spectral bands, ii) the calculation of weights tuned to the landscape being processed, iii) a fast block classification and a different band-ordering for each landscape. Our compressor reduces the size of an image to about a fourth of its original size. Our method is equivalent to LOCO-I, on 3 of the images tested it was superior. It is superior to other lossless compressors: WinZip, JPEG2000 and PNG.
我们提出了一种利用带间相关性的多光谱图像无损压缩器。每个频带被分成若干块,对这些块进行小波变换。小波系数是通过属于同一方向和空间位置的系数的线性组合来预测的。然后用基于熵的编码器对预测误差进行编码。我们最初的贡献是i)在候选预测中包含来自其他光谱波段的相同位置的系数,ii)计算调整到正在处理的景观的权重,iii)快速块分类和每个景观的不同波段排序。我们的压缩器将图像的大小减小到原始大小的四分之一左右。我们的方法与LOCO-I相当,在3张测试图像上优于LOCO-I。它优于其他无损压缩:WinZip, JPEG2000和PNG。
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引用次数: 8
Object Detection by K-Connected Seed Competition 基于k连通种子竞争的目标检测
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.34
A. Falcão, P. A. Miranda, A. Rocha, F. Bergo
The notion of "strength of connectedness" between pixels has been successfully used in image segmentation. We present an extension to these works, which can considerably increase the efficiency of object definition tasks. A set of pixels is said a ê-connected component with respect to a seed pixel when the strength of connectedness of any pixel in that set with respect to the seed is higher than or equal to a threshold. While the previous approaches either assume no competition with a single threshold for all seeds or eliminate the threshold for seed competition, we found that seed competition with different thresholds can reduce the number of seeds and the need for user interaction during segmentation. We also propose automatic and user-friendly interactive methods for determining the thresholds. The improvements are demonstrated through several segmentation experiments involving medical images.
像素间“连通性强度”的概念已被成功地应用于图像分割。我们对这些工作进行了扩展,这可以大大提高对象定义任务的效率。当一组像素相对于种子像素的任何像素的连通性强度高于或等于阈值时,该像素集被称为相对于种子像素的ê-connected组件。虽然之前的方法要么假设所有种子都没有竞争,要么取消种子竞争的阈值,但我们发现不同阈值的种子竞争可以减少种子数量和用户在分割过程中的交互需求。我们还提出了自动和用户友好的交互式方法来确定阈值。通过若干医学图像分割实验证明了该方法的有效性。
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引用次数: 6
Boolean Operations on Surfel-Bounded Objects Using Constrained BSP-Trees 基于约束bsp树的冲浪界对象布尔运算
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.17
Marcus A. C. Farias, C. Scheidegger, J. Comba, L. Velho
Point-based modeling and rendering is an active area of research in Computer Graphics. The concept of points with attributes (e.g. normals) is usually referred to as surfels, and many algorithms have been devised to their effi- cient manipulation and rendering. Key to the efficiency of many methods is the use of partitioning schemes, and usually axis-aligned structures such as octrees and KD-trees are preferred, instead of more general BSP-trees. In this work we introduce a data structure called Constrained BSP-tree (CBSP-tree) that can be seen as an intermediate structure between KD-trees and BSP-trees. The CBSP-tree is characterized by allowing arbitrary cuts as long as the complexity of its cells remains bounded, allowing better approximation of curved regions. We discuss algorithms to build CBSP-trees using the flexibility that the structure offers, and present a modified algorithm for boolean operations that uses a new inside-outside object classification. Results show that CBSP-trees generate fewer cells than axis-aligned structures.
基于点的建模和渲染是计算机图形学研究的一个活跃领域。具有属性(例如法线)的点的概念通常被称为surfels,并且已经设计了许多算法来有效地处理和渲染它们。许多方法效率的关键是使用分区方案,通常首选轴对齐结构,如八叉树和kd树,而不是更一般的bsp树。在这项工作中,我们引入了一种称为约束bsp树(cbsp树)的数据结构,它可以被视为kd树和bsp树之间的中间结构。cbsp树的特点是允许任意切割,只要它的细胞的复杂性保持有界,允许更好地逼近弯曲区域。我们讨论了利用结构提供的灵活性来构建cbsp树的算法,并提出了一种改进的布尔运算算法,该算法使用了新的内外对象分类。结果表明,cbsp树比轴向结构产生更少的细胞。
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引用次数: 5
Computing Box Dimensions from Single Perspective Images in Real Time 实时计算单视角图像的盒子尺寸
Pub Date : 2005-10-09 DOI: 10.1109/SIBGRAPI.2005.22
Leandro A. F. Fernandes, Manuel M. Oliveira, Roberto da Silva, G. Crespo
We present a new method for computing the dimensions of boxes from single perspective projection images in real time. Given a picture of a box, acquired with a camera whose intrinsic parameters are known, the dimensions of the box are computed from the extracted box silhouette and the projection of two parallel laser beams on one of its visible faces. We also present a statistical model for background removal that works with a moving camera, and an efficient voting scheme for identifying approximately collinear segments in the context of a Hough Transform. We demonstrate the proposed approach and algorithms by building a prototype of a scanner for computing box dimensions and using it to automatically compute the dimensions of real boxes. The paper also presents some statistics over measurements obtained with our scanner prototype.
提出了一种从单视角投影图像中实时计算方框尺寸的新方法。给定一个盒子的图片,用已知其内在参数的相机获取,盒子的尺寸是通过提取的盒子轮廓和两个平行激光束在其可见面上的投影来计算的。我们还提出了一种用于移动摄像机的背景去除的统计模型,以及一种用于在霍夫变换背景下识别近似共线片段的有效投票方案。我们通过构建一个用于计算盒子尺寸的扫描仪原型并使用它来自动计算真实盒子的尺寸来演示所提出的方法和算法。本文还介绍了用我们的扫描仪原型所获得的一些测量数据。
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引用次数: 2
期刊
XVIII Brazilian Symposium on Computer Graphics and Image Processing (SIBGRAPI'05)
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