Browsing by Author "Jeng, Sheng-Wen"

Now showing 1 - 3 of 3

A robust and accurate calibration method by computer vision techniques for coordinate transformation between display screens and their images
(2008-07-01)
Jeng, Sheng-Wen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A robust and accurate calibration method for coordinate transformation between display screens and their images is proposed. The images of three specially designed calibration patterns, which are a white rectangle, a black rectangle, and a dot matrix, are captured and processed sequentially to assist achieving robust extraction of relevant features from the calibration pattern images, especially the border features in the image of the display screen. Image analysis techniques of deformable template matching, local thresholding, and inverse distance-weighted interpolation are integrated to perform feature extraction and coordinate transformation to complete the calibration work. Good performance of the proposed method is demonstrated by comparing the experimental results of the method with those of a well-known calibration method.
Analytic image unwarping by a systematic calibration method for omni-directional cameras with hyperbolic-shaped mirrors
(2008-05-01)
Jeng, Sheng-Wen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
Unwarping an orimi-directional image into a perspective-view one is easy for a single-viewpoint (SVP) designed catadioptric omnidirectional camera. But misalignment between the components (such as the mirror and the lens) of this kind of camera creates multiple viewpoints and distorts the unwarped image if the SVP constraint is assumed. The SVP constraint is relaxed in this study and a systematic method is proposed to derive a set of new and general analytic equations for unwarping images taken from an omni-directional camera with a hyperbolic-shaped mirror (called a hypercatadioptric camera). The derivation is made possible by careful investigation on the system configuration and precise calibration of involved system parameters. As a verification of the correctness of the derived equations, some of the system parameters are adjusted to fit the SVP constraint, and unwarped images using the resulting simplified camera model are shown to be of no difference from those obtained by a method based on the SVP model. The generality of the proposed method so has extended the image-unwarping capability of the existing methods for the hypercatadioptric camera to tolerate lens/mirror assembly imprecision, which is difficult to overcome in most real applications. Some experimental results of image unwarping are also included to show the effectiveness of the proposed method. (C) 2007 Elsevier B.V. All rights reserved.
Improving quality of unwarped omni-images with irregularly-distributed unfilled pixels by a new edge-preserving interpolation technique
(2007-11-01)
Jeng, Sheng-Wen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new method called "edge-preserving 8-directional two-layered weighting interpolation" is proposed for interpolating unfilled pixels in a perspective-view or panoramic image resulting from unwarping an omni-image taken by a non-single-view-point hypercatadioptric camera. This method can solve the problem of edge preserving in interpolating the input image which has many irregularly-distributed unfilled pixels. Three concepts of weighting have been considered in the proposed edge-preserving interpolation process: (1) inverse-distance weighting; (2) pixel-count weighting; and (3) region-wise weighting. Good experimental results showing the effectiveness of edge preserving and its superiority to other methods are also included. (C) 2007 Elsevier B.V. All rights reserved.