Browsing by Author "Tsai, WH"

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A novel block-based authentication technique for binary images by block pixel rearrangements
(2004)
Huang, PM
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Wu, DC
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Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A novel blocked-based binary image authentication technique is proposed. The authentication signals of each 9x9 image block are placed in a selected 3x3 block within the 9x9 block. The authentication signal contains a certain relationship contributed by the standard deviation values of the other eight 3x3 blocks. Authentication signals are generated by rearranging the pixels in the selected 3x3 block. The rearrangement is designed according to a property of inverse halftoning to keep the visual change in the selected block imperceptible. By comparing the arrangement of the block pixels in a suspicious image with the extracted authentication signals, the fidelity and integrity of the image can be verified.
A novel document image segmentation method using medial axis transform
(2000)
Tzeng, CH
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Tsai, WH
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資訊工程學系
;
Department of Computer Science
A novel document image segmentation technique based on medial axis transform (MAT) proposed. The reconstruction ability of the MAT and the distance values of medial axes are utilized in the method. Firstly, the MAT is applied both to the foreground and to the background of an input document. After eliminating the unwanted medial axes of the background with some rules defined in this study, the components of the document can be grouped into homogeneous regions by reconstructing the background using the remaining medial axes. After the main regions of the input document are extracted, the distance values of the medial axes are used as features to classify text and graphic regions. Experimental results on a variety of binary and color documents indicate that the proposed method is robust to documents with any fonts, languages, and orientations, and irregular regions.
A steganographic method for images by pixel-value differencing
(2003-06-01)
Wu, DC
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Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A new and efficient steganographic method for embedding secret messages into a gray-valued cover image is proposed. In the process of embedding a secret message, a cover image is partitioned into non-overlapping blocks of two consecutive pixels. A difference value is calculated from the values of the two pixels in each block. All possible difference values are classified into a number of ranges. The selection of the range intervals is based on the characteristics of human vision's sensitivity to gray value variations from smoothness to contrast. The difference value then is replaced by a new value to embed the value of a sub-stream of the secret message. The number of bits which can be embedded in a pixel pair is decided by the width of the range that the difference value belongs to. The method is designed in such a way that the modification is never out of the range interval. This method provides an easy way to produce a more imperceptible result than those yielded by simple least-significant-bit replacement methods. The embedded secret message can be extracted from the resulting stego-image without referencing the original cover image. Moreover, a pseudo-random mechanism may be used to achieve secrecy protection. Experimental results show the feasibility of the proposed method. Dual statistics attacks were also conducted to collect related data to show the security of the method. (C) 2002 Elsevier Science B.V. All rights reserved.
Active quotation authentication in microsoft word documents using block signatures
(2005)
Liu, TY
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Tsai, WH
;
資訊工程學系
;
Department of Computer Science
Traditional message authentication does not verify the integrity and the claimed source of quotations in an anonymous message. A new active quotation authentication framework is proposed that allows a reader to authenticate the content and origin of the quotations in a citing document A block signature method is proposed that generates context-sensitive block signatures for an authoritative message, and allows quotation signatures to be generated on-the-fly for arbitrary sub passages by an anonymous author. The block signature method requires a small initial computational effort and storage requirement for block signature generation; has a small quotation signature overhead; and is efficient for quotation authentication.
Adaptive data hiding in palette images by color ordering and mapping with security protection
(2004-05-01)
Tzeng, CH
;
Yang, ZF
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Tsai, WH
;
資訊工程學系
;
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.
An incremental-learning-by-navigation approach to vision-based autonomous land vehicle guidance in indoor environments using vertical line information and multiweighted generalized hough transform technique
(1998-10-01)
Chen, GY
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Tsai, WH
;
資訊工程學系
;
Department of Computer Science
An incremental-learning-by-navigation approach to vision-based autonomous land vehicle (ALV) guidance in indoor environments is proposed. The approach consists of three stages: initial learning, navigation, and model updating. In the initial learning stage, the ALV is driven manually, and environment images and other status data are recorded automatically, Then, an off-line procedure is performed to build an initial environment model. In the navigation stage, the ALV moves along the learned environment automatically, locates itself by model matching, and records necessary information for model updating. In the model updating stage, an off-line procedure is performed to refine the learned model. A more precise model is obtained after each navigation-and-update iteration. Used environment features are vertical straight lines in camera views. A multiweighted generalized Hough transform is proposed for model matching. A real ALV was used as the testbed, and successful navigation experiments show the feasibility of the proposed approach.
Chinese dialect identification based on genetic algorithm for discriminative training of bigram model
(2000-12-01)
Tsai, WH
;
Chang, WW
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電信工程研究所
;
Institute of Communications Engineering
A minimum classification error formulation based on genetic algorithm is proposed for discriminative training of the bigram language model. Results of Chinese dialect identification were reported which demonstrate performance improvement with use of the genetic algorithm over the generalized probabilistic descent algorithm.
Chinese dialect identification using segmental and prosodic features
(2000-10-01)
Chang, WW
;
Tsai, WH
;
電信工程研究所
;
Institute of Communications Engineering
Several approaches to Chinese dialect identification based on segmental and prosodic features of speech are described in this paper. When using segmental information only, the system performs phonotactic analysis after speech utterances have been tokenized into sequences of broad phonetic classes. The second scheme comprises prosodic models which are trained to capture tone sequence information for individual dialects. Also proposed is a novel approach that examines differences between Chinese dialects at broad phonetic and prosodic levels. These algorithms were evaluated via a multispeaker read-speech mode. Simulation results indicate that the combined use of Segmental and prosodic features allows the proposed system to discriminate among three major Chinese dialects spoken in Taiwan with 93.0% accuracy. (C) 2000 Acoustical Society of America. [S0001-4966(oo)03410-X].
Color image compression using quantization, thresholding, and edge detection techniques all based on the moment-preserving principle
(1998-02-01)
Yang, CK
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Tsai, WH
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資訊工程學系
;
Department of Computer Science
A new approach to color image compression with high compression ratios and good quality of reconstructed images using quantization, thresholding, and edge detection all based on the moment-preserving principle is proposed, An input image with 24 bits per pixel is quantized into 8 bits per pixel using a new color quantization method based on the moment-preserving principle. The quantized image is then divided into n x n non-overlapping square blocks. Two representative colors for each block are computed by moment-preserving thresholding. A bit-map is then generated, consisting of 0s and 1s indicating whether the block pixels are assigned to the first color or the second according to the Euclidean distance measure. A moment-based edge detector is performed further on the bitmap of each non-uniform block. The two parameters iota and theta of a line edge with the equation of x cos theta + gamma sin theta = iota are obtained. The image is finally coded with a codebook of a 256-color palette; a 1-bit indicator for each block which specifies whether the block is uniform or not; an 8-bit color index for a uniform block, or two 8-bit color indices, a 3-bit index for theta, and a 2-bit or 3-bit index for iota for a non-uniform block. An average compression ratio of 22.49 or 33.32 can be obtained for 4 x 4 or 5 x 5 image blocks, respectively. Experimental results show the feasibility and efficiency of the proposed approach for color image compression. (C) 1998 Elsevier Science B.V, All rights reserved.
Colour image detection and matching using modified generalised Hough transform
(1996-08-01)
Lo, RC
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Tsai, WH
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資訊工程學系
;
Department of Computer Science
A new approach to 2-dimensional (2D) colour-image detection and matching using a modified version of the generalised Hough transform (GHT) is proposed. In the conventional GHT. the useful colour information existing in the input image and the relationship between each pixel and its neighbourhood are not used. Furthermore, lighting changes in the image are not usually considered. Therefore, the conventional GHT is seldom applied to colour images. In the proposed approach, lighting changes are removed using normalised colour values, Next, certain critical pixels of an input colour image whose neighbourhoods have larger variances of normalised colour values are extracted. For each critical pixel, a feature vector, which includes the normalised colour values of the pixel as well as those of the pixel's neighbours, is then constructed. A modified voting rule for the GHT is therefore proposed which is based on a similarity-measure function of the feature vectors. High maximum peaks in the cell array are searched finally as the result. The proposed method is robust for colour-image detection and matching in noisy, occlusive, and lighting-change environments, as demonstrated by experimental results.
Colour image detection and matching using modified generalised Hough transform
(1996-08-01)
Lo, RC
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A new approach to 2-dimensional (2D) colour-image detection and matching using a modified version of the generalised Hough transform (GHT) is proposed. In the conventional GHT. the useful colour information existing in the input image and the relationship between each pixel and its neighbourhood are not used. Furthermore, lighting changes in the image are not usually considered. Therefore, the conventional GHT is seldom applied to colour images. In the proposed approach, lighting changes are removed using normalised colour values, Next, certain critical pixels of an input colour image whose neighbourhoods have larger variances of normalised colour values are extracted. For each critical pixel, a feature vector, which includes the normalised colour values of the pixel as well as those of the pixel's neighbours, is then constructed. A modified voting rule for the GHT is therefore proposed which is based on a similarity-measure function of the feature vectors. High maximum peaks in the cell array are searched finally as the result. The proposed method is robust for colour-image detection and matching in noisy, occlusive, and lighting-change environments, as demonstrated by experimental results.
Copyright protection against print-and-scan operations by watermarking for color images using coding and synchronization of peak locations in frequency domain
(2006-05-01)
Chiu, YC
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Tsai, WH
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資訊工程學系
;
Department of Computer Science
A watermarking method for copyright protection of color images against print-and-scan operations is proposed. A watermark is embedded in an input image as coefficient-value peaks that are circularly and symmetrically distributed ill a middle band of the discrete Fourier transform (DFT) domain of the input image. By detecting the robust peaks in the DFT domain of a reproduced image obtained by scanning a printed version of a watermarked image, we can extract the embedded watermark to verify the copyright of the reproduced image. Experimental results are given to prove the feasibility of the proposed method.
Data hiding in images via multiple-based number conversion and lossy compression
(1998-11-01)
Wu, DC
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A novel and easy method to embed any form of secret messages into a cover image with controlled distortion is proposed. Any lossy image compressor may be applied first to a cover image to produce a lossily-processed result as the basis for embedding data in the cover image. The stego-image is produced by embedding data in each pixel of a cover image by changing its gray value without excessing the range of the gray value difference of the corresponding pixels of the cover image and its lossily-processed one. The quantity of distortion that is caused by embedding data is never in excess of that is caused by the lossy compressor. A multiple-based number system is proposed to convert the information in the secret bit stream into values to be embedded in the choosing pixels of the cover image. Pseudo-random mechanisms may be used to achieve cryptography. It is found from experiments that the values of the peaks of the signal-to-noise ratio of the stego-images are larger than those yielded by the chosen compressor, which means that the distortion in the embedding result is more imperceptible than that in the compressed one.
Data hiding in images via multiple-based number conversion and lossy compression
(1998-11-01)
Wu, DC
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A novel and easy method to embed any form of secret messages into a cover image with controlled distortion is proposed. Any lossy image compressor may be applied first to a cover image to produce a lossily-processed result as the basis for embedding data in the cover image. The stego-image is produced by embedding data in each pixel of a cover image by changing its gray value without excessing the range of the gray value difference of the corresponding pixels of the cover image and its lossily-processed one. The quantity of distortion that is caused by embedding data is never in excess of that is caused by the lossy compressor. A multiple-based number system is proposed to convert the information in the secret bit stream into values to be embedded in the choosing pixels of the cover image. Pseudo-random mechanisms may be used to achieve cryptography. It is found from experiments that the values of the peaks of the signal-to-noise ratio of the stego-images are larger than those yielded by the chosen compressor, which means that the distortion in the embedding result is more imperceptible than that in the compressed one.
Data hiding in stained glass images
(2005)
Hung, SC
;
Wu, DC
;
Tsai, WH
;
交大名義發表
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National Chiao Tung University
New methods for automatic generation of stained glass images as well as for data hiding in such images are proposed. Glass regions in stained glass images are generated by randomly sprinkled seeds and a region growing technique. The number of nodes of a tree constructed for pixel grouping in a glass region is used for data hiding in a stained glass image. A complete process for secret communication using the above technique is also proposed. Experimental results show the feasibility of the proposed methods.
Determination of head pose and facial expression from a single perspective view by successive scaled orthographic approximations
(2002-02-01)
Chang, CC
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Tsai, WH
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資訊工程學系
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Department of Computer Science
Human faces are the main organs for expressing human emotion. In this study, anew iterative approach to analyzing the head pose and the facial expression of a human face from a single image is proposed. The proposed approach extends the concept of successive scaled orthographic approximations. which was used to estimate the pose of a rigid object, to develop a method to estimate the parameters for a non-rigid object, namely, a human face. The implementation of the proposed method is simple; furthermore, no initial guess is required. The convergency property of the proposed method is also analyzed theoretically and experimentally. Experimental results show that the proposed method is robust and has a high percentage of convergency, and thus prove the feasibility of the proposed approach.
Discriminative training of Gaussian mixture bigram models with application to Chinese dialect identification
(2002-03-01)
Tsai, WH
;
Chang, WW
;
電信工程研究所
;
Institute of Communications Engineering
This study focuses on the parametric stochastic modeling of characteristic sound features that distinguish languages from one another. A new stochastic model. the so-called Gaussian mixture bigram model (GMBM), that allows exploitation of the acoustic feature bigram statistics without requiring transcribed training data is introduced. For greater efficiency, a minimum classification error (MCE) algorithm is employed to accomplish discriminative training of a GMBM-based Chinese dialect identification system. Simulation results demonstrate the effectiveness of the GMBM for dialect-specific acoustic modeling, and use of this model allows the proposed system to distinguish between the three major Chinese dialects spoken in Taiwan with 94.4% accuracy. (C) 2002 Elsevier Science B.V. All rights reserved.
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.
Embedding of any type of data in images based on a human visual model and multiple-based number conversion
(1999-12-01)
Wu, DC
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Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A novel approach to embedding any type of digital data into a cover image is proposed, which utilizes a human visual model to guarantee that the modification of the cover image is imperceptible. A quantized contrast function based on the model is constructed first. The gray values of each 3 x 3 sub-image of the cover image are used to compute, using the function, a range of gray levels with the same contrast as that of the central pixel of the sub-image. The embedding process proceeds by replacing the gray value of the central pixel by one of the values in the range. This guarantees that the changes be imperceptible. The data to be embedded is treated as a binary stream and is partitioned into a number of sub-streams. A multiple-base number conversion mechanism is used to convert each sub-stream of data into values which are then embedded in the central pixels of sub-images. The embedded data can be extracted out from the resulting stego-image without referencing the original image. Experimental results show that the proposed method is feasible. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Estimation of moving vehicle locations using wheel shape information in single 2-D lateral vehicle images by 3-D computer vision techniques
(1999-04-01)
Lai, CC
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Tsai, WH
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資訊工程學系
;
Department of Computer Science
an approach to the estimation of moving lateral vehicle locations for driving assistance using wheel shape information in single 2-D vehicle images by 3-D computer vision techniques is proposed. The location scheme is supposed to be performed on a vehicle with a camera mounted on the front bumper. An analytical solution is applied to estimate locations of the lateral vehicle. Firstly, the rear wheel shape of a lateral vehicle moving in a nearby lane is imaged. By using the Hough transform, the projected wheel shape, which is an ellipse, is detected. Secondly. the equation of the detected ellipse is used to infer the orientation angle of the lateral vehicle with respect to the camera view direction. Finally, the center of the ellipse shape is used to determine the relative position of the lateral vehicle with respect to the camera lens center, Moreover, an edge-point verification algorithm is utilized to extract the ellipse shape more precisely in the image processing stage. Both computer simulated and real images are tested and good experimental results show the effectiveness of the proposed approach for estimating lateral vehicle locations. The results are useful for driving assistance and vehicle collision avoidance and are discussed in detail. (C) 1999 Elsevier Science Ltd. All rights reserved.