Computer Graphics, Image Processing, and Vision, 1998. Proceedings. SIBGRAPI '98. International Symposium on

The point containment predicate which specifies if a point is part of a mathematically defined shape or not is a crucial problem in computer graphics. This paper presents a stroking technique that counteracts the main disadvantage of point containment algorithms: their quadratic time complexity with increasing resolution. It is also presented an efficient algorithm to perform simultaneously the fi... View full abstract»

In this paper we present a method for applying 2D textures onto composite and articulated objects defined by implicit functions. The method generates a particle system associated with the gradient vector field of an implicit function which acquires texture coordinates at a support surface. By extending this method to composite objects, an implicit surface may change its shape in time, while mainta... View full abstract»

This paper describes a novel method for recovering the perspective geometry of textured surfaces from local spectral analysis. We recover 3-D orientation of planar surfaces based on angular properties of the local spectral description of the surface markings. We also show a geometrical relationship between local spectral components and the vanishing point of the texture plane. Our method is a two-... View full abstract»

The problem of determining the generators of brain electromagnetic activity has no unique solution. The only way to deal this problem, sometimes denominated “the problem of the non-uniqueness”, is to restrict the set of possible solutions by using either physiological or mathematical constraints or a combination of both. The main purpose of this work is to propose a method for obtainin... View full abstract»

This paper describes the architecture of an integrated multi-modal sensory (vision and touch) computational system. We propose to use an approach based on robotics control theory that is motivated by biology and developmental psychology, in order to integrate the haptic and visual information processing. We show some results carried out in simulation and discuss the implementation of this system u... View full abstract»

Boron carbide microscopic images may present grains crossed by twins (or macles) viewed as straight lines in the inner part of each grain. The twins preclude the segmentation because they are very similar to the grain borders. To eliminate the twins a preprocessing step, which relies on mathematical morphology tools, is applied to the image. The main operation used is a directional opening, using ... View full abstract»

This paper describes a system architecture that enables the use of different techniques of warping and morphing applied to various classes of graphical objects (images, surfaces, plane curves, volumetric data, implicit surfaces etc.) Combinations of warping and morphing techniques can lead to more powerful and expressive results. The possibility of experimenting with alternative techniques for dis... View full abstract»

The localization of the neural generators of the brain's electromagnetic activity based an electrical or magnetic recordings requires the solution of an ill-posed inverse problem. In its general form, this inverse problem has no unique solution. The only way to deal with this problem, is to restrict the set of possible solutions by using either anatomical or mathematical constraints or a combinati... View full abstract»

A novel disparity estimation method is presented that increases the robustness of the estimator by replacing the classical approach of dynamic programming with finding the maximum flow in a graph. Once solved, the minimum cut associated to the maximum flow yields a disparity surface for the whole image at once. The results show improved depth estimations as well as better handling of depth discont... View full abstract»

Oil reservoirs searching is based on several exploratory methods, which produce a large quantity of data that must be interpreted and analyzed by geologists. Graphic systems can help these tasks by providing three-dimensional representations to convey information in a more natural and efficient way to the users. Therefore, they are typical scientific visualization applications. This paper presents... View full abstract»

Random modeling is an important technique for solving hard problems in coding, quantitative description and restoration of images. In the sixties. Matheron introduced the theory of Random Closed Sets (RACS), that permits the creation of models by morphological transformations of primitive processes. A limitation of this theory is that not all transformation of a RACS produces a new RACS. Recently ... View full abstract»

Reduced pyramids, i.e. pyramids without analysis filters are known to produce excellent results when used for lossless signal and image compression. The paper introduces a novel method for the construction of reduced pyramids with synthesis filters adapted to the orientation of local image features. It is shown that this construction produces more accurate interpolation than conventional reduced p... View full abstract»

The problem of matching two images can be posed as finding a displacement field which assigns each point of the reference image to a point in the test image. In this paper we present an iterative algorithm to estimate the probability density function relating the intensity distribution of two MR scanners, based on the topological constraints embedded in the elastic matching model. The set of image... View full abstract»

This paper investigates computer vision techniques for three-dimensional reconstruction having as source of information non-professional images captured from cameras of arbitrary position and orientation. The main purpose is to compose a methodology for 3D reconstruction, aiming specially at its use in the documentation of historic buildings and monuments through their three-dimensional modeling. ... View full abstract»

This work reports developments on a system for 3D visualization based on “Holoprojection”, a depth coding technique. This system allows visualization using several planes of depth of textured images, such that all depth cues are present under certain limits. The 3D volume can be observed with no auxiliary devices, such as stereo glasses View full abstract»

Due to the concentration of users in certain regions of the virtual world, distributed virtual reality systems-DVRS-may become unbalanced, resulting in low performance and bad utilization of system resources. The authors studied this problem and proposed a queueing model and load balancing algorithms to reduce these effects. Some experiments showed how the utilization and response time of the syst... View full abstract»

The correction of handwritten word skew is an arduous task that must be independent of due to style and writing conditions variations. We propose here a morphology-based method to detect and correct handwritten word skew in the treatment of dates written on bank checks. Our aim is to limit the number of parameters and heuristic features necessary for a good skew correction. Our approach is based o... View full abstract»

An image compression/decompression method is proposed, based on a new interpolation formula of Hermite-Birkhoff type. It is based on a function representation that uses a truncated multipoint Taylor (MT) series. Given a regularly tabulated image, first spatial derivatives (up to a chosen order) are computed by a FFT algorithm. Secondly a knot placing strategy selects sample point positions. The im... View full abstract»

This paper presents a system for automatic extraction of the user-entered data from Brazilian bankchecks. We have assumed that the layout structure of bankchecks is standardized, that any bankcheck can be identified through the MICR line and that a sample of the background pattern is available for every bankcheck. Based on these assumptions, a template is designed for extracting the user-entered i... View full abstract»

This paper describes a technique developed to analyze and recognize paper based electronic circuit diagram images. One of the key aspects of this recognition system relies on the identification of feature points used to guide a new line vectorization method developed for circuit diagram images. The feature paints are also used as a discriminate element in the symbol classification process. Once th... View full abstract»

We measured narrow-band human frequency response functions for four harmonic angular frequency filters whose test frequencies were centered at either 2, 4, 8 or 16 cycles using a supra-threshold summation method. The four filter response functions of 17 experimental conditions (each) were measured eight to nine times among five observers (NAS, MMM, ERB, MC and TPL). The results show that, for the ... View full abstract»

The paper is devoted to the pattern recognition procedure based on the set of expert rules with unprecisely formulated weights understood as conditional probabilities. Adopting the probabilistic model, the recognition algorithm is derived and evaluation of its probability of misclassification is given. Furthermore, the case with both expert rules and the learning set is considered. The proposed al... View full abstract»

This paper describes a method to correct lens distortion for digital cameras. A simple but effective distortion model using local spatial transformation will be used. In addition, the effect of effective focal length on the distortion model will be considered, and we will discuss how to introduce this factor to enhance the model. Finally we have some theoretical analysis and experiments demonstrat... View full abstract»