Browsing by Author "Yang, ZF"

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Adaptive data hiding in palette images by color ordering and mapping with security protection
(2004-05-01)
Tzeng, CH
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Yang, ZF
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Tsai, WH
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資訊工程學系
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Department of Computer Science
Palette images are widely used in multimedia and Internet applications. In this paper, a new method for data hiding in palette images with security protection by color ordering and mapping, as well as parameter randomization, is proposed. First, image pixels are classified as data embeddable or nonembeddable, and only the former ones are used to embed secret data. The proposed idea of data hiding is based on the use of a new type of color-ordering relationship, from which a color-mapping function is defined with binary values as output. When a secret data bit is to be embedded, a data-embeddable pixel is selected, and its color is adjusted to make the output of the color-mapping function equal to the secret bit value. The embedded secret data can be extracted correctly and quickly from the resulting stego-image by merely inspecting the outputs of the color-mapping function. Indetectability of the secret information embedded by the proposed method is also analyzed and confirmed. Furthermore, a number of possible security enhancement measures based on parameter randomization in the data-embedding process are proposed to protect the hidden data in the stego-image. The randomization effect is created by the use of a secret key and a number of random number-generating functions. The proposed data hiding method was tested with a variety of palette images. The experimental results show that secret data can be embedded and extracted successfully without producing visual artifacts in the cover image. A good balance between stego-image quality and data-embedding capacity can be achieved, which proves the efficiency and feasibility of the proposed method for practical applications.
Embedded signature-based authentication by channel statistics using watermarking techniques
(2002)
Yang, ZF
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Tsai, WH
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資訊工程學系
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Department of Computer Science
This study examines the feasibility of using channel statistics to perform embedded signature-based authentication. Doing so is an attempt to view a reference watermark embedded with signature as side information. The reference watermark is extracted to determine channel statistics, based on the Bayes theorem, and used to extract the embedded signature. The reliability of the extracted signature and the uncertainty of the channel status are also measured. Experimental results demonstrate that the reliability and uncertainty measures based on channel statistics are meaningful, and that the embedded signature can survive high-quality JPEG compression and manipulation such as negation.
Using parallel line information for vision-based landmark location estimation and an application to automatic helicopter landing
(1998-08-01)
Yang, ZF
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Tsai, WH
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資訊工程學系
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Department of Computer Science
An approach to landmark location estimation by computer vision techniques is proposed. The objective is to derive the position and the orientation of the landmark with respect to the vehicle by a single image. Such information is necessary for automatic vehicle navigation. This approach requires lower hardware cost and simple computation. The vanishing points of the parallel lines on the landmark are used to detect the landmark orientation. The detected vanishing points are used to derive the relative orientation between the landmark and the camera, which is then utilized to compute the landmark orientation with respect to the vehicle. The size of the landmark is used to determine the landmark position. Sets of collinear points are extracted from the landmark and their inter-point distances are computed. The positions of the collinear point sets are evaluated and used to determine the landmark position. Landing site location estimation by using the identification marking H on the helicopter landing site for automatic helicopter landing is presented as an application of the proposed approach. Simulations and experiments have been conducted to prove the feasibility of the proposed approach. (C) 1998 Elsevier Science Ltd. All rights reserved.
Viewing corridors as right parallelepipeds for vision-based vehicle localization
(1999-06-01)
Yang, ZF
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Tsai, WH
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資訊工程學系
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Department of Computer Science
An approach to vision-based vehicle localization by viewing corridors as a combination of right parallelepipeds is proposed. The objective is to derive the orientation and lateral position of a vehicle in a right parallelepiped corridor, These two kinds of information are all that is needed for vehicles to navigate safely in a right parallelepiped corridor. This approach offers low hardware cost and simple computation. Only one camera mounted on the vehicle is needed, and analytic formulas are derived for computing the vehicle location. The information source is the corridor ceiling. Two orthogonal sets of parallel lines on the corridor ceiling are used to detect the vanishing line of the ceiling. An equation is developed to derive the vehicle orientation by utilizing the detected vanishing line. Also, based on the observation of the variation of image line slopes when we move laterally, another equation is established to evaluate the relative lateral position of the vehicle by utilizing the line slope of the ceiling line pointing forward. Experiments have been conducted, and acceptable vehicle localization results have been obtained, to prove the feasibility of the proposed approach.
Watermarking approach to embedded signature-based authentication by channel statistics
(2003-04-01)
Yang, ZF
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
Embedded signature-based authentication is a highly promising watermarking method for solving high-level authentication problems. This work proposes such a watermarking approach using channel statistics evaluated from a reference watermark. The basic concept is to consider the problem to be an example of communications with side information, which is the reference watermark embedded in the host with the signature at the sender site. At the receiver site, the reference watermark is first extracted to determine channel statistics, which are used to generate information about signature reliability. Three kinds of information are derived, including a reliability measure, an entropy measure, and an authenticated signature. Experimental results establish that the measures of reliability and uncertainty are meaningful, and that the embedded signature can survive high-quality JPEG compression and manipulations such as negation, cropping, replacement, and modification. (C) 2003 Society of Photo-Optical Instrumentation Engineers.