Browsing by Author "Tsai, Wen-Hsiang"

Now showing 1 - 20 of 41

A Convenient Vision-Based System for Automatic Detection of Parking Spaces in Indoor Parking Lots Using Wide-Angle Cameras
(2014-07-01)
Shih, Shen-En
;
Tsai, Wen-Hsiang
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
A convenient indoor vision-based parking lot system using wide-angle fisheye-lens or catadioptric cameras is proposed, which is easy to set up by a user with no technical background. Easiness in the system setup mainly comes from the use of a new camera model that can be calibrated using only one space line without knowing its position and direction, as well as from the allowance of convenient changes in detected parking space boundaries. After camera calibration based on the new camera model is completed, parking space boundary lines are automatically extracted from input wide-angle images by a modified Hough transform with a new cell accumulation scheme, which can generate more accurate equal-width curves using the geometric relations of line positions and directions. In addition, the user may easily add or remove the boundary lines by single clicks on images, and parking spaces can be segmented out by region growing with the use of the boundary lines. Finally, vacant parking spaces can be detected by a background subtraction scheme. A real vision-based parking lot has been established and relevant experiments conducted. Good experimental results show the correctness, feasibility, and robustness of the proposed methods.
A covert communication method via spreadsheets by secret sharing with a self-authentication capability
(2013-02-01)
Lee, Che-Wei
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new covert communication method with a self-authentication capability for secret data hiding in spreadsheets using the information sharing technique is proposed. At the sender site, a secret message is transformed into shares by Shamir's (k, n)-threshold secret sharing scheme with n = k + 1, and the generated k + 1 shares are embedded into the number items in a spreadsheet as if they are part of the spreadsheet content. And at the receiver site, every k shares among the k + 1 ones then are extracted from the stego-spreadsheet to recover k + 1 copies of the secret, and the consistency of the k + 1 copies in value is checked to determine whether the embedded shares are intact or not, achieving a new type of blind self-authentication of the embedded secret. By dividing the secret message into segments and applying to each segment the secret sharing scheme, the integrity and fidelity of the hidden secret message can be verified, achieving a covert communication process with the double functions of information hiding and self-authentication. Experimental results and discussions on data embedding capacity, authentication precision, and steganalysis issues are also included to show the feasibility of the proposed method. (c) 2012 Elsevier Inc. All rights reserved.
A data hiding method based on information sharing via PNG images for applications of color image authentication and metadata embedding
(2013-07-01)
Lee, Che-Wei
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new data hiding method via PNG images based on Shamir's (k, n)-threshold secret sharing scheme is proposed. The coefficients of the polynomial used by the Shamir's method are taken as carriers to carry given data. The data to be hidden then are transformed into partial shares and embedded into the alpha-channel plane of a cover PNG image. Undesired white noise created in the resulting stego-image is removed by skillfully mapping the computed share values into suitable ranges in the embedding process. An important application of the proposed method to color image authentication is also proposed, with detailed authentication algorithms for PNG images presented. Compared with existing methods, the proposed image authentication method possesses the merits of losslessness during image authentication, high sensitivity to image alterations, good tampering localization capability, and very low false acceptance and rejection ratios. Experimental results proving the effectiveness of the proposed methods are also included. (C) 2013 Elsevier B.V. All rights reserved.
A Lossless Large-Volume Data Hiding Method Based on Histogram Shifting Using an Optimal Hierarchical Block Division Scheme
(2011-07-01)
Lee, Che-Wei
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A lossless large-volume data hiding method based on histogram shifting is proposed. The method is based on a scheme of hierarchically dividing a cover image into smaller blocks for data embedding using the histogram shifting technique, which yields a large data hiding capacity and results in a high stego-image quality. A technique for recursive looking-ahead estimation of the maximum data hiding volume at the lowest level of the block-division tree structure is proposed to yield an optimal data hiding result. The technique is shown to break a bottleneck of data-hiding-rate increasing at the image block size of 8 x 8, which is found to exist in other histogram-shifting methods. Four ways of block divisions are used, and one of them is selected optimally in each tree level of block divisions. A series of experiments have been conducted, and superiority of the proposed method to other related methods is shown by comparing the respective experimental results. A good property of the proposed method observed in the experiments is also pointed out, that is, the data hiding rate yielded by the proposed method increases without degrading the stego-image quality, which is an unusual phenomenon in data hiding researches.
A new approach to covert communication via PDF files
(2010-02-01)
Lee, I-Shi
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new covert communication method via PDF files is proposed. A secret message, after being encoded by a special ASCII code and embedded at between-word and between-character locations in the text of a PDF file, becomes invisible in the window of a common PDF reader, creating a steganographic effect for secret transmission through the PDF file. Experimental results show the feasibility of the proposed method. (C) 2009 Elsevier B.V. All rights reserved.
A New Data Hiding Method via Revision History Records on Collaborative Writing Platforms
(2014-02-01)
Lee, Ya-Lin
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new data hiding method via collaboratively-written articles with forged revision history records on collaborative writing platforms is proposed. The hidden message is camouflaged as a stego-document consisting of a stego-article and a revision history created through a simulated process of collaborative writing. The revisions are forged using a database constructed by mining word sequences used in real cases from an English Wikipedia XML dump. Four characteristics of article revisions are identified and utilized to embed secret messages, including the author of each revision, the number of corrected word sequences, the content of the corrected word sequences, and the word sequences replacing the corrected ones. Related problems arising in utilizing these characteristics for data hiding are identified and solved skillfully, resulting in an effective multiway method for hiding secret messages into the revision history. To create more realistic revisions, Huffman coding based on the word sequence frequencies collected from Wikipedia is applied to encode the word sequences. Good experimental results show the feasibility of the proposed method.
A New Data Transfer Method via Signal-Rich-Art Code Images Captured by Mobile Devices
(2015-04-01)
Lee, Ya-Lin
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new type of signal-rich-art image for applications of data transfer, called signal-rich-art code image, is proposed. The created code image is visually similar to a preselected target image and, with a given message embedded, achieves the effect of the so-called signal-rich art. With its function similar to that of a QR code, such a type of image is produced by encoding the message into a binary bit stream, representing the bits by binary code patterns of 2 x 2 blocks, and injecting the patterns into the target image by a novel image-block luminance modulation scheme. Each signal-rich-art code image may be printed or displayed and then is recaptured using a mobile-device camera. Skillful techniques for counting the number of pattern blocks and recognition of code patterns are also proposed for message extraction from the recaptured version of the signal-rich-art code image. Good experimental results and a comparison of them with those of an existing alternative method show the feasibility and superiority of the proposed new data transfer method.
A New Secure Image Transmission Technique via Secret-Fragment-Visible Mosaic Images by Nearly Reversible Color Transformations
(2014-04-01)
Lee, Ya-Lin
;
Tsai, Wen-Hsiang
;
交大名義發表
;
National Chiao Tung University
A new secure image transmission technique is proposed, which transforms automatically a given large-volume secret image into a so-called secret-fragment-visible mosaic image of the same size. The mosaic image, which looks similar to an arbitrarily selected target image and may be used as a camouflage of the secret image, is yielded by dividing the secret image into fragments and transforming their color characteristics to be those of the corresponding blocks of the target image. Skillful techniques are designed to conduct the color transformation process so that the secret image may be recovered nearly losslessly. A scheme of handling the overflows/underflows in the converted pixels' color values by recording the color differences in the untransformed color space is also proposed. The information required for recovering the secret image is embedded into the created mosaic image by a lossless data hiding scheme using a key. Good experimental results show the feasibility of the proposed method.
A New Steganographic Method Based on Information Sharing via PNG Images
(2010-01-01)
Lee, Che-Wei
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
多媒體工程研究所
;
Department of Computer Science
A new steganographic method via PNG images based on the information sharing technique is proposed. The coefficients of the polynomial functions of the Shamir's (k, n)-threshold secret sharing method are utilized as carriers of a given secret data string to be hidden to generate shares. The shares then are embedded into the alpha-channel plane of a cover PNG image. The resulting stego-image with perceptible white noise is further removed by mapping computed share values into suitable ranges. Appropriate measures for enhancing the security of the proposed method are also described. Experimental results show the effect of the proposed method.
A New Two-Omni-Camera System with a Console Table for Versatile 3D Vision Applications and Its Automatic Adaptation to Imprecise Camera Setups
(2011)
Shih, Shen-En
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new two-omni-camera system for 3D vision applications and a method for adaptation of the system to imprecise camera setups are proposed in this study. First, an efficient scheme for calibration of several omni-camera parameters using a set of analytic formulas is proposed. Also proposed is a technique to adapt the system to imprecise camera configuration setups for in-field 3D feature point data computation. The adaptation is accomplished by the use of a line feature of the console table boundary. Finally, analytic formulas for computing 3D feature point data after adaptation are derived. Good experimental results are shown to prove the feasibility and correctness of the proposed method.
A Novel Method for Lateral Vehicle Localization by Omni-Cameras for Car Driving Assistance
(2009)
Wu, Chih-Jen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A lateral vehicle localization method by omni-image analysis is proposed for car driving assistance. The method estimates analytically the position and orientation of a lateral vehicle by utilizing the geometric properties of a circular-shaped wheel image of the lateral car taken by a single onmi-camera with a hyperboloidal-shaped mirror. Analytical solutions are made possible for fast computation by a special arrangement of affixing the omni-camera on the frontal car bumper at the height of the wheel. Experimental results showing good data estimation precision are included to prove the feasibility of the proposed method.
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.
A Secret-Sharing-Based Method for Authentication of Grayscale Document Images via the Use of the PNG Image With a Data Repair Capability
(2012-01-01)
Lee, Che-Wei
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new blind authentication method based on the secret sharing technique with a data repair capability for grayscale document images via the use of the Portable Network Graphics (PNG) image is proposed. An authentication signal is generated for each block of a grayscale document image, which, together with the binarized block content, is transformed into several shares using the Shamir secret sharing scheme. The involved parameters are carefully chosen so that as many shares as possible are generated and embedded into an alpha channel plane. The alpha channel plane is then combined with the original grayscale image to form a PNG image. During the embedding process, the computed share values are mapped into a range of alpha channel values near their maximum value of 255 to yield a transparent stego-image with a disguise effect. In the process of image authentication, an image block is marked as tampered if the authentication signal computed from the current block content does not match that extracted from the shares embedded in the alpha channel plane. Data repairing is then applied to each tampered block by a reverse Shamir scheme after collecting two shares from unmarked blocks. Measures for protecting the security of the data hidden in the alpha channel are also proposed. Good experimental results prove the effectiveness of the proposed method for real applications.
A Space-Mapping Method for Object Location Estimation Adaptive to Camera Setup Changes for Vision-Based Automation Applications
(2012-01-01)
Wu, Chih-Jen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new space-mapping method for object location estimation, which is adaptive to camera setup changes, for use in various automation applications is proposed. The location of an object appearing in an image is estimated by mapping image coordinates of object points to corresponding real-world coordinates using a mapping table, which is constructed in two stages, with the first stage for establishing a basic table using bilinear interpolation in the camera manufacturing environment and the second for adapting the table to changes of camera heights and orientations in the application field. Analytic equations for table adaptation are derived by skillful utilization of both image formation and camera geometry properties. Good experimental results are shown to prove the feasibility of the proposed method.
A Two-Omni-Camera Stereo Vision System With an Automatic Adaptation Capability to Any System Setup for 3-D Vision Applications
(2013-07-01)
Shih, Shen-En
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A stereo vision system using two omni-cameras for 3-D vision applications is proposed, which has an automatic adaptation capability to any system setup before 3-D data computation is conducted. The adaptation, which yields the orientations and distance of the two omni-cameras, is accomplished by detecting and analyzing the horizontal lines appearing in the omni-images acquired with the cameras and a person standing in front of the cameras. Properties of line features in environments are utilized for detecting more precisely the horizontal lines that appear as conic sections in omni-images. The detection work is accomplished through the use of carefully chosen parameters and a refined Hough transform technique. The detected horizontal lines are utilized to compute the cameras' orientations and distance from which the 3-D data of space points are derived analytically. Compared with a traditional system using a pair of projective cameras with nonadjustable camera orientations and distance, the proposed system has the advantages of offering more flexibility in camera setups, better usability in wide areas, higher precision in computed 3-D data, and more convenience for nontechnical users. Good experimental results show the feasibility of the proposed system.
Adaptation of Space-Mapping Methods for Object Location Estimation to Camera Setup Changes - A New Study
(2009)
Wu, Chih-Jen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new space-mapping method for object location estimation which is adaptive to camera Setup changes in various applications is proposed. The location of in object appearing in an image is estimated by mapping image coordinates of object points to corresponding real-world coordinates using a mapping table, which is constructed in two stages, with the first for establishing a basic table using bilinear interpolation and the second for adapting it to changes of camera heights and orientations. Analytic equations for Such adaptation are derived based oil image formation and camera geometry properties. Good experimental results are shown to prove the feasibility of the proposed method.
An Omni-vision Based Localization Method for Automatic Helicopter Landing Assistance on Standard Helipads
(2010-01-01)
Wu, Chih-Jen
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
多媒體工程研究所
;
Department of Computer Science
An omni-vision-based localization method for automatic helicopter landing assistance on a helipad with a circled H-shape is proposed. The landing process includes two stages: approaching and alignment. Three types of image features, circle, line, and point, are used to derive skillfully analytic equations for computing the helicopter height, distance, and orientation with respect to the landing site. Experimental results with good location estimation accuracy are also shown.
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.
CONSTRUCTION OF LOW-DISTORTED MESSAGE-RICH VIDEOS FOR PERVASIVE COMMUNICATION
(2016-01-01)
You, Zhen-Yu
;
Tsai, Yu-Shiuan
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
Many types of multimedia can be used to accommodate information for pervasive communication. Messages may be injected into them by information hiding techniques and extracted for various purposes. Such multimedia with messages embedded are called message-rich multimedia. A new method for creating message-rich videos is proposed in this study for people to exchange messages by display-and-imaging operations. A message is firstly embedded in a given video by a technique of injecting peak values into the DFT spectrum of each video frame. The resulting message-rich video, when displayed on a TV or monitor, is then recorded with a smart-phone camera as another video. The message in the recorded video is finally extracted for visual inspection. This way of message transmission can be used for covert communication, secret message exchanges, etc. Good experimental results show the feasibility of the proposed method.
Data hiding in binary images with distortion-minimizing capabilities by optimal block pattern coding and dynamic programming techniques
(2007-08-01)
Lee, I-Shi
;
Tsai, Wen-Hsiang
;
資訊工程學系
;
Department of Computer Science
A new method for data hiding in binary images based on block pattern coding and dynamic programming with distortion-minimizing capabilities is proposed. Up to three message data bits can be embedded into each 2 x 2 block in an input image by changing the block's pixel pattern into another, which represents the value of the message data bits as a code according to a block pattern encoding table. And extraction of hidden message data is accomplished by block pattern decoding. To minimize the resulting image distortion, two optimization techniques are proposed. The first is to use multiple block pattern encoding tables, from which an optimal one is selected specifically for each input image, and the second is to use a dynamic programming algorithm to divide the message data into bit segments for optimal embedding in a sense of minimizing the number of binary bit flippings. Accordingly, not only more data bits can be embedded in an image block on the average, but the resulting image distortion is also reduced in an optimal way. Experimental results are also included to show the effectiveness of the proposed approach.