1,721,349 research outputs found
Model-based discontinuity evaluation in the DCT domain
No full textThe discrete cosine transform (DCT) has been used for compressing videos or images with standards like MPEG and JPEG. In this paper, we derive DCT properties related to a standard discontinuity and propose a model-based discontinuity evaluation technique in the DCT domain. This technique consists of a direction verification and a position alignment method with an evaluation criterion. The direction verification and position alignment causes the DCT coefficients to be of the centralized form, which enables an evaluation regardless of various positions and directions of discontinuities. The evaluation criterion examines the standard position and evaluates the magnitude of a discontinuity by using the properties of the ideal step model. Although the detected discontinuities are rough in a low-resolution image for the size (8 x 8 pixels) of DCT blocks, experimental results show that this technique is fast in processing and robust against noise. (C) 2001 Elsevier Science B.V. All rights reserved.X119sciescopu
Estimating optical flow by tracking contours
No full textWe present a novel method of velocity field estimation for the points on moving contours in a 2-D image sequence. The method determines the corresponding point in a next image frame by minimizing the curvature change of a given contour point. As a first step, snakes are used to locate smooth curves in 2-D imagery. Thereafter, the extracted curves are tracked continuously computing the corresponding point for each contour point. (C) 1997 Published by Elsevier Science B.V.X114sciescopu
Contour matching using epipolar geometry
No full textMatching features computed in images is an important process in multiview image analysis. When the motion between two images is large, the matching problem becomes very difficult. In this paper, we propose a contour matching algorithm based on geometric constraints. With the assumption that the contours are obtained from images taken from a moving camera with static scenes, we apply the epipolar constraint between two sets of contours and compute the corresponding points on the contours. From the initial epipolar constraints obtained from corner point matching, candidate contours are selected according to the epipolar geometry, contour end point constraints, and contour distance measures. In order to reduce the possibility of false matches, the number of match points on a contour is also used as a selection measure. The initial epipolar constraint is refined from the matched sets of contours. The algorithm can be applied to a pair or two pairs of images. All of the processes are fully automatic and successfully implemented and tested with various real images.X1130sciescopu
Edge representation with fuzzy sets in blurred images
No full textThis paper proposes a representation of edges in blurred images using the concept of fuzzy sets when the images are degraded by various asymmetric and local blurring factors. The proposed representation is expressed by fuzzy membership functions, and it can serve as a relative index of blur. The membership function is derived from the distribution of intensity gradients and the symmetricity of gradient magnitudes, and the function is calculated directly from the blurred image without identifying the point spread function or restoring image. In this way, the fuzzy edge representation describes edges with their degradation states by fuzzy memberships instead of the binary description of edges. The index of fuzziness reflects the average amount of ambiguity presented in a fuzzy set, and the moments denote an object in the image quantitatively. These measures are adopted to illustrate the effectiveness of the representation in locally blurred images. (C) 1998 Elsevier Science B.V. All rights reserved.X1112sciescopu
A corner preserving surface inference algorithm using 3D convolution
No full textA corner preserving 3D convolution operator is proposed. This vector convolution operator is a different version of Guy and Medioni's Diabolo field which is used for inferring surface normals from sparse and noisy 3D data. The new operator, named Quadratic field, is made by revolving a set of quadratic functions around the vertical axis. Other than the convolution operator, Guy and Medioni's method in surface normal inference is followed. Analysis and experimental results showed that the new operator performs better in recovering cornered surfaces from sparse 3D data. (C) 2001 Elsevier Science B.V. All rights reserved.X11sciescopu
Ambiguity distance: an edge evaluation measure using fuzziness of edges
No full textMost edge detection methods have parameters (threshold values or standard deviation of Gaussian operator for smoothing) to be set, and these parameters make much influence on the outputs of the detectors. In this paper we propose an objective parameter evaluation measure. We evaluate parameters based on the edge ambiguity measures of existence, location and formation. The existence and location ambiguity measures are derived from comparing fuzzy memberships of edgeness with detected edges, and the formation ambiguity measure assesses the connectedness and the total number of edge point in an edge image with respect to the image size. The parameters which produce the least ambiguous edges of a detection method for an image are selected as significant ones. No iterative visual interaction or prior knowledge of edges are needed for these evaluation measures, The effectiveness of the measures is demonstrated by applying the ambiguity measures to synthetic and real images. (C) 2002 Elsevier Science B.V. All rights reserved.X113sciescopu
Outlier correction from uncalibrated image sequence using the Triangulation method
No full textWe propose a robust algorithm for estimating the projective reconstruction from image features using the RANSAC-based Triangulation method. In this method, we select input points randomly, separate the input points into inliers and outliers by computing their reprojection error, and correct the outliers so that they can become inliers. The reprojection error and correcting outliers are computed using the Triangulation method. After correcting the outliers, we can reliably recover projective motion and structure using the projective factorization method. Experimental results showed that errors can be reduced significantly compared to the previous research as a result of robustly estimated projective reconstruction. (c) 2005 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.X116sciescopu
Correlation and prediction of gene expression level from amino acid and dipeptide composition of its protein
No full textBackground: A large number of papers have been published on analysis of microarray data with particular emphasis on normalization of data, detection of differentially expressed genes, clustering of genes and regulatory network. On other hand there are only few studies on relation between expression level and composition of nucleotide/protein sequence, using expression data. There is a need to understand why particular genes/proteins express more in particular conditions. In this study, we analyze 3468 genes of Saccharomyces cerevisiae obtained from Holstege et al., ( 1998) to understand the relationship between expression level and amino acid composition. Results: We compute the correlation between expression of a gene and amino acid composition of its protein. It was observed that some residues ( like Ala, Gly, Arg and Val) have significant positive correlation ( r > 0.20) and some other residues ( Like Asp, Leu, Asn and Ser) have negative correlation ( r < - 0.15) with the expression of genes. A significant negative correlation ( r = - 0.18) was also found between length and gene expression. These observations indicate the relationship between percent composition and gene expression level. Thus, attempts have been made to develop a Support Vector Machine ( SVM) based method for predicting the expression level of genes from its protein sequence. In this method the SVM is trained with proteins whose gene expression data is known in a given condition. Then trained SVM is used to predict the gene expression of other proteins of the same organism in the same condition. A correlation coefficient r = 0.70 was obtained between predicted and experimentally determined expression of genes, which improves from r = 0.70 to 0.72 when dipeptide composition was used instead of residue composition. The method was evaluated using 5-fold cross validation test. We also demonstrate that amino acid composition information along with gene expression data can be used for improving the function classification of proteins. Conclusion: There is a correlation between gene expression and amino acid composition that can be used to predict the expression level of genes up to a certain extent. A web server based on the above strategy has been developed for calculating the correlation between amino acid composition and gene expression and prediction of expression level http:// kiwi. postech. ac. kr/ raghava/ lgepred/. This server will allow users to study the evolution from expression data.open1137sciescopu
Contour motion estimation from image sequences using curvature information
No full textThis paper presents a novel method of velocity field estimation for the points on moving contours in a 2-D image sequence. The method determines the corresponding point in a next image frame by considering the curvature change of a given point on the contour. In traditional methods, there are errors in optical flow estimation for the points which have low curvature variations since those methods compute solutions by approximating normal optical flow. The proposed method computes optical flow vectors of contour points minimizing the curvature changes. As a first step, snakes are used to locate smooth curves in 2-D imagery. Thereafter, the extracted curves are tracked continuously. Each point on a contour has a unique corresponding point on the contour in the next frame whenever the curvature distribution of the contour varies smoothly. The experimental results showed that the proposed method computes accurate optical flow vectors for various moving contours. (C) 1997 Pattern Recognition Society. Published by Elsevier Science Ltd.X1114sciescopu
Contour matching: a curvature-based approach
No full textThe lack of information about tangential velocity makes velocity estimation erroneous in contour matching. Classical methods use the normal velocity, together with some smoothness constraints, since the tangential velocity cannot be recovered. This paper presents a contour matching method that computes displacements with a criteria of minimum curvature differences. The first derivative of tangential velocity is available from the image intensities and is related to the contour curvature. We compute the velocities using the curvature as well as the normal component. Consequently, the estimation error due to the tangential component is reduced substantially. A contour having occluding parts leads to mismatching. Our method determines occluding parts before the contour matching by analyzing the change of curvature distribution. Experimental results showed that the proposed method computes accurate velocity vectors for various moving contours. (C) 1998 Elsevier Science B.V.X1111sciescopu
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