Proceedings. XV Brazilian Symposium on Computer Graphics and Image Processing

This article presents a method for the segmentation of substructures based on exploratory factor analysis. In this approach, a set of high-dimensional shape-related variables is examined with the purpose of finding clusters with strong correlation. This clustering can potentially identify regions that have anatomic significance and thus lend insight to morphometric investigations. View full abstract»

Functional magnetic resonance imaging (fMRI) uses MRI to noninvasively map areas of increased neuronal activity in human brain without the use of an exogenous contrast agent. Low signal-to-noise ratio of fMRI images makes it necessary to use sophisticated image processing techniques, such as statistical parametric map (SPM), to detect activated brain areas. This paper presents a new technique to o... View full abstract»

This paper describes the current state of research and development of a system for the partial automation of quantitative funduscopy. Image processing techniques are used to segment the optic disk and estimate the parameters of the circumference associated with it. The global objective is to facilitate the diagnosis of pathologies like systemic arterial hypertension and diabetes mellitus. View full abstract»

In this paper we present a new approach which integrates the T-surfaces model and isosurface generation methods in a general framework for surface reconstruction in 3D medical images. T-surfaces is a deformable model based on a triangulation of the image domain, a discrete surface model and an image threshold. Two types of isosurface generation methods are considered: the continuation ones and the... View full abstract»

Distribution of the visualization process over the World Wide Web allows remote access to expensive resources, and the cooperation amongst teams of experts that are located in different places. This paper presents an architecture and a corresponding prototype implementation of a distributed system for visualization and sonification of scientific data. The distribution is accomplished by the additi... View full abstract»

We present an output-sensitive occlusion culling algorithm for densely occluded dynamic scenes where both the viewpoint and objects move arbitrarily. Our method works on a regular grid that represents a volumetric discretization of the space and uses the opaque regions of the scene as virtual occluders. We introduce new techniques of efficient traversal of voxels, object discretization and occlusi... View full abstract»

With the evolution of medical image acquisition techniques, the capacity and fidelity of image-based diagnosis were extended. The current trend is to acquire information using multiple sources to help medical diagnosis, but the integration of the multivariate data into a single 3D representation is non-trivial. Techniques for the visualization of multimodal volume data have been developed with the... View full abstract»

This paper describes a pipeline for the acquisition and rendering of large real-world environments. In the acquisition phase, we use a laser rangefinder to capture the geometry of an environment, and a digital camera to capture its colors. In the rendering phase, we use a cluster of commodity PCs to render high-resolution images of the environment at interactive frame rates. In this paper, we desc... View full abstract»

Synthetic aperture radar (SAR) images are corrupted by speckle noise, which degrades the quality and interpretation of the images. Speckle removal provides a better interpretability of SAR images if the technique performs the filtering without loss of spatial resolution and preserves fine details and edges. This work aims to redefine the neighborhood areas around the noisy pixel and in this area t... View full abstract»

The problem of image data fusion includes several techniques for data integration from different sensors about a given object. The process can be divided in two stages: (a) pixel interpolation on each observed image to equalize their resolutions; and (b) synthesis of the fused image using the interpolated images. This work proposes the use of projection onto convex sets (POCS) techniques in both s... View full abstract»

Digital change detection methods have been broadly divided into either pre-classification spectral change detection or post-classification change detection. Since all spectral change detection methods are based on pixel-wise operations, or scene-wise plus pixel-wise operations, accuracy in image registration and scene-to-scene radiometric normalization is more critical for these methods than for o... View full abstract»

Texture information is useful for image data browsing and retrieval. The goal of this paper is to present a texture classification system for remote sensing images aimed at the administration of large collections of those images. The proposed classifier is a hybrid system composed by an unsupervised neural network and a supervised one. Starting from a small portion of the image (pattern) the syste... View full abstract»

This paper presents a new method for structuring and tracking of objects in video sequences. Our approach is based on image moments and the BSP-tree data structure. We use invariant properties of these moments to construct a BSP-tree and determine an ellipsis that approximates the object's shape. Then, we employ this information to track objects frame by frame through the image sequence. The metho... View full abstract»

We address the problem of filtering three-dimensional sparse data representing real objects. The main application is to eliminate points that are not structured on surfaces. Points classified as organized can be the input for other processes. An accumulation process infers the organization of each input element. The tensorial fields used in our method act as three-dimensional structuring elements.... View full abstract»

We present a hybrid system using computer vision and graphics methods that effectively combines fast automatic 3D model extraction with view-dependent texture mapping for the purpose of real-time person-to-person 3D video teleconferencing. In our approach the problem of creating a dense disparity map is bypassed. We compute only a sparse geometric model, which is textured from multiple cameras usi... View full abstract»

An improved Zernike moment using as a region-based shape descriptor is presented. The improved Zernike moment not only has rotation invariance, but also has scale invariance that the unimproved Zernike moment does not have. The experimental results show that the improved Zernike moment has better invariant properties than unimproved Zernike moment using as region-based shape descriptor. View full abstract»

The watershed transform has been used for image segmentation relying mostly on image gradients. However, background noise tends to produce spurious gradients, that cause over-segmentation and degrade the output of the watershed transform. Also, low-contrast edges produce gradients with small magnitudes, which may cause different regions to be erroneously merged. In this paper, a new technique is p... View full abstract»

Cement is an essential material for the development of the civil construction. The analysis of cement-based materials is useful in the evaluation of mechanical properties, water absorption, air permeability and evolution of hydration degree. The latter is the motivation of this paper. New advantageous techniques of analysis based on the image information are possible using electronic microscopy. W... View full abstract»

The watershed transform and the morphological reconstruction are two of the most important operators for image segmentation in the framework of mathematical morphology. In many situations, the segmentation requires the classical watershed transform of a reconstructed image. In this paper, we introduce the IFT-watershed from gray scale marker-a method to compute at same time, the reconstruction and... View full abstract»

This paper presents an automatic method to assess telangiectasia degreeing, by estimating the reduction of the varicose area from pre to post-treatment using digital image analysis techniques. First both images are geometrically transformed and color space reduced, in order to make them suitable for processing. Next, the varicose veins are segmented via watershed transform and the varicose areas i... View full abstract»

We show how to use affine arithmetic to represent a parametric curve with a strip tree. The required bounding rectangles for pieces of the curve are computed by exploiting the linear correlation information given by affine arithmetic. As an application, we show how to compute approximate distance fields for parametric curves. View full abstract»

CoMo is a prototype of a collaborative 3D geometric modeling environment designed to support temporally and geographically dispersed work teams. In this environment participants may work in different parts of the space and have distinct perspective viewing of the space. Maintaining workspace awareness, therefore, becomes much more difficult. In this paper we present graphics solutions we adopted f... View full abstract»

We present a fast and memory efficient algorithm that generates a manifold triangular mesh S with or without boundary passing through a set of unorganized points P/spl sub//spl Rscr//sup 3/ with no other additional information. Nothing is assumed about the geometry or topology of the sampled manifold model, except for its reasonable smoothness. The speed of our algorithm is derived from a projecti... View full abstract»

A new three-dimensional reconstruction technique is presented that uses an integer control parameter, denoted /spl beta/, to produce a family of models from a given set of planar cross-sections. Parameter /spl beta/ supports multiple choices for solving the correspondence problem, i.e., the problem of deciding which regions from two consecutive cross-sections must be connected into a single compon... View full abstract»