Browsing by Author "Lee, YK"

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A new approach for recognizing multifont Chinese characters used in a special application
(1996-05-01)
Chen, LH
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Lee, YK
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資訊工程學系
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Department of Computer Science
Many approaches for recognizing all of the 5401 commonly used Chinese characters have been proposed, but they are complex, For some applications such as cheques, receipts, addresses, in Chinese, etc., only a limited set of printed characters is needed, but they are usually require a real time response and a high recognition rate. Based on this reason, here we provide a simpler approach to meet these two requirements. The approach takes horizontal strokes, vertical ones and crossings among these strokes as the character features. A fast modified Hough transform is provided to extract these features, it satisfies an important stroke property that a dotted line must not be a real stroke. In the learning stage, an error measure is defined and an optimal stroke matching algorithm is proposed to establish an accurate random model for each type of characters. In the recognition stage, another error measure is defined and a nearly-optimal matching algorithm is presented to speed up the recognition process. It is worth mentioning that the approach does not use any thinning process. Some experimental results are also provided to show the effectiveness of the proposed recognizer.
An adaptive digital image watermarking technique for copyright protection
(1999-11-01)
Lee, CH
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Lee, YK
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資訊工程學系
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Department of Computer Science
An adaptive digital image watemarking technique is proposed in this paper. The proposed method exploits the sensitivity of human eyes to adaptively embed a visually recognizable watermark in an image without affecting the perceptual quality of the underlying host image. In addition, the watermark will still be present if some lossy image processing operations such as low-pass filtering, median filtering, resampling, requantization, and lossy JPEG image compression are applied to the watermarked image. Experimental results show the effectiveness of the proposed watermarking method.
High capacity image steganographic model
(2000-06-01)
Lee, YK
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Chen, LH
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資訊工程學系
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Department of Computer Science
Steganography is an ancient art of conveying messages in a secret way that only the receiver knows the existence of a message. So a fundamental requirement for a steganographic method is imperceptibility; this means that the embedded messages should not be discernible to the human eye. There are two other requirements, one is to maximise the embedding capacity, and the other is security. The least-significant bit (LSB) insertion method is the most common and easiest method for embedding messages in an image. However, how to decide on the maximal embedding capacity for each pixel is still an open issue. An image steganographic model is proposed that is based on variable-size LSB insertion to maximise the embedding capacity while maintaining image fidelity. For each pixel of a grey-scale image, at least four bits can be used for message embedding. Three components are provided to achieve the goal. First, according to contrast and luminance characteristics, the capacity evaluation is provided to estimate the maximum embedding capacity of each pixel. Then the minimum-error replacement method is adapted to find a grey scale as close to the original one as possible. Finally, the improved grey-scale compensation, which takes advantage of the peculiarities of human visual system, is used to eliminate the false contouring effect. Two methods, pixelwise and bitwise, are provided to deal with the security issue when using the proposed model. Experimental results show effectiveness and efficiency of the proposed model.
Object-based image steganography using affine transformation
(2002-09-01)
Lee, YK
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Chen, LH
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資訊工程學系
;
Department of Computer Science
The typical model of steganography has led the prisoners' problem, in which two persons attempt to communicate covertly without alerting the warden. The general way to achieve this task is to embed the message in an innocuous-looking medium. In this paper, an object-based geometric embedding technique is proposed for solving the prisoners' problem. The main idea is to embed secret data through distorting a given object and the distorted object still looks natural. In the embedding process, the secret message is first converted into coefficients of an affine transformation. Then, the coordinates of each pixel of a selected object in the cover-image are recomputed by this affine transformation. Since these coefficients are restricted in a specific range, the transformed object looks natural. In the extracting process, a coarse-to-fine iterative search is proposed to accelerate the object location and the message extraction. Experimental results show that all transformed objects can be located precisely and the whole hidden message can be extracted correctly even if the stego-image is stored in various compression formats and rates. Furthermore, the embedded message is robust enough when the stego-image format is converted from GIF to JPEG, and vice versa.
Secure error-free steganography for JPEG images
(2003-09-01)
Lee, YK
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
The typical model of steganography has led the prisoners' problem, in which two persons attempt to communicate covertly without alerting the warden, that is, only the receiver knows the existence of the message sent by the sender. One available way to achieve this task is to embed the message in an innocuous-looking medium. In this paper, we propose a variation of the Quantization Index Modulation (QIM) for solving the prisoners' problem. We also propose a theorem to show that the error of mean intensity value of an image block caused by JPEG compression is bounded. The proposed method embeds the messages to be conveyed by modifying the mean intensity value, and the resulting stego-image can be stored in the JPEG format with a low quality setting. Besides, a specific pattern caused by using the QIM embedding method is also identified, and this pattern will be removed using the proposed embedding method. Experimental results and the proposed theorem show that the hidden message is error-free against the JPEG distortion under the quality setting as low as 25. Furthermore, the existence of the hidden message is not only visually imperceptible but also statistically undetectable.
Selective deposition of gold nanoparticles on SiO(2)/Si nanowires for molecule detection
(2005-04-01)
Sheu, JT
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Chen, CC
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Huang, PC
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Lee, YK
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Hsu, ML
The selective deposition of gold nanoparticles on the surface of N-(2-Aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS)-pretreated silicon nanowire (SiNW)s for molecule detection was demonstrated. The SiNWs were fabricated by scanning probe lithography (SPL) and tetramethyl ammonium hydroxide (TMAH) wet etching. The width and height of the SiNWs were 60 nm and 10 nm, respectively. The gold nanoparticles were synthesized by the chemical reduction method. The electronic properties of the SiNWs in response to the binding of different molecules on the surface of the SiNWs subsequently were discussed. A dynamic observation of the change in conductance was conducted to monitor the reaction between gold nanoparticles and the AEAPTMS-pretreated surface of the SiNWs. The reaction of gold nanoparticles on the surface of the SiNWs took about 750 s before conductance saturation. Finally, an engineered enzyme, KSI-126C, with a thiol terminal was designed to bind with the gold nanoparticles on the surface of the SiNWs. Shifts in turn-on voltage in I-V(ds) characteristics have clearly been observed after the binding of molecules and gold nanoparticles.