Browsing by Author "Chia, TL"

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A method for rectifying grid junctions in grid-coded images using cross ratio
(1996-08-01)
Chia, TL
;
Chen, Z
;
Yueh, CJ
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
In the grid-coding technique, the accurate grid junction locations are vital to the surface computation. Noise arising from the imaging formation and processing processes will jeopardize the computation accuracy. The objective of this study is to make use of the geometric property of cross ratio to improve the accuracy of grid junction locations in grid-coded images., A method is devised to regenerate grid junctions from the original (i.e., raw) junction data of an image. Through a statistical error analysis, we show that the regenerated junction data are generally more accurate than the old ones in the image taken from a wide range of viewing angles.
A method for rectifying grid junctions in grid-coded images using cross ratio
(1996-08-01)
Chia, TL
;
Chen, Z
;
Yueh, CJ
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
In the grid-coding technique, the accurate grid junction locations are vital to the surface computation. Noise arising from the imaging formation and processing processes will jeopardize the computation accuracy. The objective of this study is to make use of the geometric property of cross ratio to improve the accuracy of grid junction locations in grid-coded images., A method is devised to regenerate grid junctions from the original (i.e., raw) junction data of an image. Through a statistical error analysis, we show that the regenerated junction data are generally more accurate than the old ones in the image taken from a wide range of viewing angles.
A parallel algorithm for generating chain code of objects in binary images
(2003-02-01)
Chia, TL
;
Wang, KB
;
Chen, LR
;
Chen, Z
;
資訊科學與工程研究所
This paper addresses parallel execution of chain code generation on a linear array architecture. The contours in the proposed algorithm are viewed as a set of edges (or contour segments) that can be traced by a top-down contour tracing method to generate the chain codes for the outer and inner object contours. A parallel algorithm that contains the chain code generating rules and operations needed is also described, and the algorithm is mapped onto a one-dimensional systolic array containing [(1)/(2)(N + 1)] processing elements (PEs) to devise this architecture. The architecture extracts the contours of objects and quickly generates the corresponding chain codes after the image data in all rows are inputted in a linear fashion. The total processing time for generating the chain codes in an N x N image is O(3N). By doing so, the real-time requirement is fulfilled and its execution time is independent of the image content. In addition, a partition method is developed to process an image when the parallel architecture has a fixed number of PEs; say two or more. The total execution time for an N x N image by employing a fixed number of PEs is N(N + 1)/M + 2(M - 1), when M is the fixed number of PEs. (C) 2002 Elsevier Science Inc. All rights reserved.
Determination of feature correspondences in stereo images using a calibration polygon
(1997-09-01)
Chiu, JM
;
Chen, Z
;
Chuang, JH
;
Chia, TL
;
資訊科學與工程研究所
In this paper, we propose a novel approach to solving the vertex/edge correspondence problem for stereo images. Assume an object is placed on a calibration plate (C-plate) and two perspective views of them are given. The C-plate vertex correspondence, determined by cross-ratios, is used to reduce the search space for determining object vertex/edge correspondence. First, the correspondence of object edges lying on the C-plate (called the object base edges) is considered. This is because the subpolygons obtained from the division of the C-plate by the extended line of each of these base edges are viewpoint invariant, i.e. the cross-ratio of each of their vertices in different images will have equal value. Assume that at least one of the base edges is visible in each image. Since a visible object base edge has to be an object boundary edge in an image, only object boundary edges will be considered for the cross-ratios check for the associated subpolygons as well as other geometric constraint checks in determining the object base vertex/edge correspondence. These geometric constraints include (i) the position of the edges along the boundary of object faces, and (ii) the division of the C-plate vertices by the extended lines of these edges. Based on one of the determined corresponding base edge pairs, the correspondence of all other edges can be determined by constraints similar to (i). Finally, some additional viewpoint invariant measures about the object faces and the C-plates are introduced to resolve the ambiguity problem which may arise for specific viewpoints and some special object shapes. The proposed approach only needs 2-D image data and has no constraint on the number of vertices of an object face. Experimental results are presented for some polyhedral as well as curved objects. (C) 1997 Pattern Recognition Society. Published by Elsevier Science Ltd.
Parallel distance transforms on a linear array architecture
(2002-04-30)
Chia, TL
;
Wang, KB
;
Chen, Z
;
Lou, DC
;
資訊科學與工程研究所
Distance transformation (DT) has been widely used for image matching and shape analysis. In this paper, a parallel algorithm for computing distance transformation is presented. First, it is shown that the algorithm has an execution time of 6N - 4 cycles, for an N x N image using a parallel architecture that requires [N/2] parallel processors. By doing so, the real time requirement is fulfilled and its execution time is independent of the image contents. In addition, a partition method is developed to process an image when the parallel architecture has a fixed number of processing elements (PEs); say two or more. The total execution time for an N x N image by employing a fixed number of PEs is 2[N-2/M + 2(M - 1)], when M is the fixed number of PEs. (C) 2002 Elsevier Science B.V. All rights reserved.
Parallel execution of a connected component labeling operation on a linear array architecture
(2003-03-01)
Wang, KB
;
Chia, TL
;
Chen, Z
;
Lou, DC
;
資訊科學與工程研究所
This work presents a novel parallel algorithm and architecture for finding connected components in an image. Simulation results indicate that the proposed algorithm has an execution time of N-2 +6N-4 cycles for an NxN image using an architecture containing 4 parallel processors. The proposed hardware can process a 128 x 128 image in 0.8574 ms and uses only 4 processors, compared to 0.85 ms and 128 processors for the work of Ranganathan et al. [14], and 94.6 ms and 16384 processors for the MPP [22]. Among the advantages of the novel architecture are modularity, expandability, regular data flow, and simple hardware. These properties are extremely desirable for VLSI implementations. Additionally, the execution time of the algorithm is independent of its image content; thus, it is quite flexible.
Pose determination of a cylinder using reprojection transformation
(1996-09-02)
Huang, JB
;
Chen, Z
;
Chia, TL
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Extracting useful and robust feature points from a cylinder image for 3D pose determination is a relatively difficult task, since there are no feature points or lines on the cylinder. In this study, a key vector from a cylinder image is found to yield a transformation. The cylinder is then ''reprojected'' from the original image to obtain a new image using the transformation. The new image reveals some important features capable of determining the 3D cylinder position robustly. The proposed method can yield an exact and analytical solution without the requirement of using any special marks, extra equipment or assumptions. Additionally, a problem in which both circles on the cylinder are not completely visible due to the viewing angle can be resolved by this method. Finally, experimental results are provided to verify the theory and show the robustness of our method.