Proceedings XIV Brazilian Symposium on Computer Graphics and Image Processing

In this paper we present an algorithm for estimating the rotation index of a closed loop from the number of singular points on it. On the basis of this index we also devise a procedure that guarantees to have an arbitrary loop being traced only once. Combining this procedure with a higher-order stepping algorithm, a robust intersection technique is resulted. View full abstract»

We present an algorithm for computing a robust adaptive polygonal approximation of an implicit curve in the plane. The approximation is adapted to the geometry of the curve because the length of the edges varies with the curvature of the curve. Robustness is achieved by combining interval arithmetic and automatic differentiation. View full abstract»

This paper presents an object-oriented approach for creating multi-region non-manifold models with NURBS. The main motivation is that the geometry and shape of realistic engineering objects are intrinsically complex, usually composed by several materials and regions. Therefore, automatic and/or adaptive meshing algorithms have become revealed themselves quite useful to increase the reliability of ... View full abstract»

To reconstruct a topologically consistent 3D surface model is a challenging problem. In this paper we present an algorithm that estimates from a range image, without registering and converting it into a volumetric data, the most probable topology of a surface to be reconstructed. In our algorithm we start with a closed initial mesh and preserve its "closeness" during the reconstruction process. So... View full abstract»

In this paper we discuss the use of high-level verification on handwritten numeral strings. First of all, we introduce the concept of levels of verification and present the baseline system used to carry out the experiments. Two different strategies were developed: absolute and one-to-one verifiers. A thorough error analysis is also presented in order to identify under which conditions high-level v... View full abstract»

Prototype selection is primarily effective in improving the classification performance of nearest neighbor (NN) classifier and also partially in reducing its storage and computational requirements. This paper reviews some prototype selection algorithms for NN classification and experimentally evaluates their performance using a number of real data sets. Finally, new approaches based on combining t... View full abstract»

The paper presents a procedure to implement an automatic system for supervised pattern recognition with an ongoing learning capability. The purpose is to continuously increase the knowledge of the system and, accordingly, to enhance its performance in classification tasks. The nearest neighbor rule is employed as the central classifier and several techniques are added to cope with the increase in ... View full abstract»

The paper recalls the idea of classification trees in OCR (optical character recognition) systems and proposes a technique for the automatic design of these classification trees. The design of both the classification trees and of the classification operators are based on training from sample pairs of observed-ideal images, allowing the development of customized OCRs. View full abstract»

Scale spaces allow us to organize, compare and analyse differently sized structures of an object. The linear scale space of a monochromatic image is the solution of the heat equation using that image as an initial condition. Alternatively, this linear scale space can also be obtained by applying Gaussian filters of increasing variances to the original image. The authors compare (by looking at theo... View full abstract»

In order to fully achieve automated mammogram analysis one has to tackle two problems: classification of radial, circumscribed microcalcifications, and normal samples; and classification of benign, malignant, and normal samples. How to extract and select the best features from the images for classification is a very difficult task, since all of those classes are basically irregular textures with a... View full abstract»

The article reports on the development of a system for automatic analysis of retinal angiographic images. Particularly, we focus on the segmentation of the blood vessels in these images. We started by implementing a previously known technique based on mathematical morphology. Due to some shortcomings of this method for our data, we have developed a new approach based on the continuous wavelet tran... View full abstract»

An important application of fractals is image texture analysis. The main aspect of fractal geometry used in this application is the concept of fractal dimensions to characterize the texture-scaling behavior. A new idea is presented: the use of fractals for texture identification in multiband image analysis. This is not a simple extension of the usual characterization of multifractal from its local... View full abstract»

The paper presents a novel Euclidean distance transform algorithm formulated under the mathematical morphology approach. The distance transform is an erosion by a structuring function dependent on the distance metric used. To achieve high speed performance, the squared Euclidean distance structuring function is decomposed into a family of four one-dimensional two-point structuring functions. The e... View full abstract»

Machine design of a signal or image operator involves estimating the optimal filter from sample data. In principle, relative to the error measure used, the optimal filter is best; however, owing to design error, the designed filter might not perform well. In general it is suboptimal. The envelope constraint involves using two humanly designed filters that form a lower and upper bound for the desig... View full abstract»

DNA chips (i.e., microarrays) biotechnology is a hybridization (i.e., DNA matching) based process that makes it possible to quantify the relative abundance of mRNA from two distinct samples by analysing their fluorescence signals. This technique requires robotic placement (i.e., spotting) of thousands of cDNAs (i.e., complementary DNA) in an array format on glass microscope slides which provide ge... View full abstract»

The paper introduces a new connected filter which provides image simplification in terms of flat zone and graylevel reduction. This filtering consists of the application of morphological operators to the histogram. It is done because each object in the image has a significative distribution of graylevels in the histogram. In other words, it is enough to classify the distributions in the histogram ... View full abstract»

This paper presents image-synthesis techniques to define, animate and visualize scenes simulating the behavior of the open-sea surface. Wave modeling is obtained by means of the bump mapping technique. Wave texture, defined by noise functions, is applied by means of a solid-space animation technique to generate surface animation. An implementation based on the Phong model is used to determine diff... View full abstract»

In order to obtain models of complex virtual environments, there are many solutions that make use of image-based rendering techniques. When using a set of images to represent an element in space as a billboard, there are some problems related with the shading calculations, once these elements are just planes in space. This article presents a new approach for shading objects represented by images, ... View full abstract»

We present methods for synthesizing 3D shape features on subdivision surfaces using multiscale procedural techniques. Multiscale synthesis is a powerful approach for creating surfaces with different levels of detail. Our methods can also blend multiple example multiresolution surfaces, including procedurally-defined surfaces as well as captured models. View full abstract»

This paper presents a novel approach to the real-time rendering of complex scenes problem. Up to the present date, a huge number of acceleration techniques have been proposed, although most are geared towards a specific kind of scene. Instead of using a single, or a fixed set of rendering acceleration techniques, we propose the use of several, and to select the best one based on the current viewpo... View full abstract»

Many image compression schemes perform the discrete cosine transform (DCT) to represent an image in frequency space. An analysis of a suite of images confirms that the luminance AC coefficients can be modeled by a Laplacian distribution. The distribution model can be used to drop the insignificant coefficients. In this paper we develop an image-adaptive JPEG encoding algorithm that incorporates gl... View full abstract»

This paper proposes a new method for image denoising with edge preservation, based on image multiresolution decomposition by a redundant wavelet transform. In our approach, edges are implicitly located and preserved in the wavelet domain, while noise is filtered out. At each resolution, the coefficients associated to noise and coefficients associated to edges are modeled by Gaussians, and a shrink... View full abstract»

In this paper, we propose a video watermarking technique to hide copyright information in MPEG motion vector. In this method, watermark is embedded in larger value motion vectors, and specially in the less phase angle changed component. Then, the motion vector is modified into a new bitstream from which the watermark information can be easily retrieved. From the experimental results, it indicates ... View full abstract»

We propose an integrated framework in which local perception and close manipulation skills are used in conjunction with a high-level behavioral interface based on a "smart object" paradigm as support for a virtual agent to perform autonomous tasks. In our model, virtual "smart objects" encapsulate information about possible interactions between the agent and its environment, including sub-tasks de... View full abstract»