• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.851-854
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• 1998

Recently efficient image coding algorithms using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficients are encoded with a tree structure, called zerotree, which can exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very effective, especially in low bit rate image coding. In this paper, two zerotree image coding algorithms, EZW and SPIHT, are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientations as well as its scale.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.211-214
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• 2002

Recently efficient image coding using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficient are enrolled with a tree structure, called zerotree, which ran exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very especially in low bit rate image coding. In this paper, two zerotree image rolling algorithm, EZW and SPHIT are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientation as well as its scale.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.161-164
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• 2000

Recently efficient image coding using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficient are encoded with a tree structure, called zerotree, which can exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very especially in low bit rate image coding. In this paper, two zerotree image coding algorithm, EZW and SPHIT are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientation as well as its scale.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.785-792
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• 2004

In this paper, we propose a fast and efficient method that improves the performance of embedded zerotree wavelet(EZW) algorithm introduced by Sharipo． In the EZW algorithm, two bits are allocated for a symbol, but it is inefficient for compression and the zerotree coding wastes much time at encoding. In this paper, in order to increase the efficiency of compression, it will be allocated a variable bit for a symbol at each subband. To reduce the encoding time, we use a backscan method and lifting scheme instead of filter bank in wavelet transform. Experimental result are shown that the algorithm suggested in this paper has a better performance about 0.3∼1.5㏈ PSNR while the encoding time was speeded up more than 2-10 times compared with the EZW algorithm.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.743-746
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• 2001

An improved zerotree-structure based wavelet coding algorithm is proposed. When the descendants of a significant coefficient are all zerotree, its four-childs are coded respectively in conventional EZW. But in the proposed algorithm, a new symbol is assigned for the significant coefficient. Entropy for both methods are analyzed and new coding scheme is proposed. The experimental results show that the Proposed algorithm has a better performance than the original EZW algorithm.

• Journal of Korea Society of Industrial Information Systems
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• v.6 no.1
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• pp.39-47
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• 2001

A blocked zerotree coding algorithm for compression of subband image is proposed. Significance of blocks with respect to a certain threshold are coded with a set of transition rules for the significance of blocks. Significant blocks are quantized by vector quantization. The basic idea for this coding approach are: 1) Subband images are coded by blocks, 2) Important blocks based on the significance of blocks are coded and quantized, 3) Multiband codebook which is composed of sub-codebooks dedicated for each threshold and subband level is adapted to produce good reproduction vectors for vector quantization. The compression results are similar to Shapiro's zerotree coding even though ours are obtained without entropy coding of bit streams from blocked zerotree encoder. If an entropy coding is applied to the bitstream, PSNR will be improved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.4B
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• pp.471-478
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• 2001

웨이블릿 변환은 영상을 위치 정보와 주파수 정보를 가지고 표현함으로서 다른 변환 방식과는 큰 차이를 보여준다. 웨이블릿 변환된 2-D 영상은 인간의 시각 체계(Human Visual System)에 적정한 양자화 및 부호화를 위한 계층적 구조를 제공한다. 인간의 시각이 민감하게 감지하는 성분은 정확하게 부호화하고 다른 성분은 적절한 정보의 손실을 적용하는 원리를 이상적으로 적용할 수 있다. 이런 웨이블릿 변환의 통계적 특성을 이용한 제로트리(zerotree) 부호화 기법은 영상 전체에서 의미 있는 계수를 선별하여 약속된 우선 순서대로 부호화함으로써 매입파일(embedded file)을 생성한다. 본 논문에서는 Shspiro 가 제안한 EZW(embedded Zerotree wavelets) 알고리즘을 개선하여 화소 단위가 아닌 블록 단위로 부호화 함으로서 좀더 나은 성능을 가진 알고리즘을 제안하였다.

• Proceedings of the IEEK Conference
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• 2002.06d
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• pp.97-100
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• 2002

In this paper, we propose a watermarking technique that embeds a digital watermark into digital images for the proof of owner or copyright protection. Proposed algorithm is based on discrete wavelet transform. Zerotree structure defined by Shapiro's embedded zerotree wavelet(EZW) algorithm is used. In the proposed algorithm, a digital watermark is embedded on only significant wavelet coefficients chosen by QSWT for the robustness of the algorithm. In other words, only the values of significant wavelet coefficients are modified in accordance with the given watermark pattern. We use the relationship among neighboring coefficients when modifying chosen coefficients to keep good image quality. Visual recognizable patterns such as binary images are used as a watermark. The experimental results show that the proposed algorithm has robustness under a variety of attacks such as JPEG compression, sharpening and blurring and also show that it has a better performance in PSNR comparing with other algorithms.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06b
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• pp.45-50
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• 1999

이진 영상의 압축은 디지털 도서관, 팩시밀리 전송, 문서 입출력 시스템과 같이 한정된 대역폭과 저장 공간을 가진 응용 분야에서 절실히 요구되고 있다. 현재 많은 영상 압축 알고리즘이 채택하고 있는 대역분할 기법을 문서와 같은 이진 영상의 압축에 적용한다면, 점진적 전송, 축소영상을 통한 빠른 검색 등의 장점을 얻을 수 있다. 그러나, 이진 영상 신호가 두 단계의 휘도 값을 가지므로, 이에 적합한 대역분할 방법과 산술부호기를 선택하여야 한다. 본 논문에서는 표본화-XOR 대역분할 기법을 선택하여, 알파벳 수의 증가를 막고 공간영역에서 국부적인 성질을 얻을 수 있다 또한, 넓은 단일-색 영역을 Zerotree로 대표하여 부호화 되는 신호의 수를 줄이고, 대역분할 구조에서 예측성의 저하를 막기 위한 적절한 조건화문맥과 새로운 부호를 선택한다. 이진 영상에 적합한 대역분할 방법과 산술부호기를 선택하여, 대역분할의 장점과 우수한 압축 성능을 달성할 수 있다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.55-62
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• 2012

EZW, also known as Embedded Zerotree Wavelet, is a technique that allows transforming original images into wavelet, then again compressing images using the transformed data. This algorithm demonstrates a simple structure and remarkable effectiveness. This paper has reformed the EZW to improve a compression efficiency. Fundamentally, EZW evaluates the priority level of wavelet-transformed data and stores them into four different categories considering the priority level of the data as well as their location information. The four categories are represented as the symbols P, N, Z, and T. Here, P and N correspond to the volume of data and the priority level whereas Z and T show the location information of data. Each letter is stored through the process of dominant pass. However, here is when the data of Z and T are stored redundantly which lead to unnecessary increase of data volume. In this paper, we propose a modified version of Embedded Zerotree Wavelet algorithm, which is designed to efficiently reduce the volume of redundantly stored data using four additionally inserted symbols. We name it EEZW, Extended Embedded Zerotree Wavelet. The proposed algorithm demonstrates the efficiency verified by a number of image and confirms an outstanding result through the PSNR(Peak Signal To Noise Rate) values, which measure their quality of images.