• Journal of the Korea Society of Computer and Information
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• v.7 no.1
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• pp.112-119
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• 2002

We propose an enhanced wavelet packet image coder algorithm which is based on the coefficients partition. The proposed wavelet packet image coder uses the first-order entropy to reduce the total compression time, and achieves low bit rates and rate-distortion performance by the zero-tree based coding using correlations between coefficients partition. This new algorithm represents new parent-children relationships for reducing image reconstruction error using the correlations between each frequency subbands and then the wavelet packet coefficients are Partitioned by a new order. The computer simulations demonstrate higher PSNR under the same bit rate and improved image compression time and enhanced rate control compare with conventional algorithms. From the simulation results, it is shown that the encoding and decoding process of proposed coder are much simple and accurate than present method against texture images , which include many mid-frequency elements.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.3
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• pp.23-33
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• 2011

In this paper, the wavelet image coder, that can encode the bit-level information of wavelet coefficients, is proposed. The proposed coder is used the modified EZW algorithm and significant coefficient array that has bit level information of the wavelet coefficients to reduce the memory requirement in coding process. The significant coefficient array is two dimensional data structure that has bit level information of the wavelet coefficients. The proposed algorithm performs the coding of the significance coefficients and coding of bit level information of wavelet coefficients at a time by using the significant coefficient array. Experimental results show a better or similar performance of the proposed method when compared with conventional embedded wavelet coding algorithm. Especially, the proposed algorithm performs stably without image distortion at various bit rates with minimum memory usage by using the significant coefficient array.

• 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 the Korean Institute of Telematics and Electronics S
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• v.34S no.10
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• pp.112-119
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• 1997

Zerotreeimage coding is known as a simple and effective image comprssion algorithm. It has the property that the compression is generated in order of improtance. Conventionally, a fixed threshold is applied to the entire wavelet coefficients regardless of frequency and local features of an image. In this paper, we propose a new zerotree coding scheme with adaptive threshold. The adaptive threshold is determined by human visual characteristics. It is shown that the image quality of the proposed method is better than that of the conventional method.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.9
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• pp.76-84
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• 1999

EZW proposed by Shapiro is based on a zerotree constructed in a way that a parent coefficient in a subband is related to four child coefficients in the next finer subband of similar orientation. This fixed treeing based on 1-to-4 parent-child is suitable to exploti hierachical correlations among subbands but not to exploit spatial correlations within a subband. A new treeing by Joo, et al. is suggested to simulatneously exploit those two correlatins by extending parent-child relationship in a flexible way. The flexible treeing leads to increasing the number of symbols and lowering entorpy comparing to the fixed treeing, and therefore a better compression can be resulted. In this paper, we suggest two techniques to suppress the increasing of symbols. First, a probing bit is generated to avoid redundant scan for insignivicant coefficients. Second, since all subbands do not always require the same kind of symbol-set, produced symbols are re-symbolized into binary codes according to a pre-defined procedure. Owing to those techniques, all symbols are generated as binary codes. The binary symbols can be entropy-coded by an adaptive arithmetic coding. Moerover, the binary symbol stream can give comparatively good performances without help of additional entropy coding. Our proposed coding scheme is suggested in two modes: binary coding mode and arithmetic coding mode. We evaluate the effectivenessof our modifications by comparing with the original EZW.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.417-420
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• 2000

점진적 영상 전송과 저해상도에서도 높은 PSNR를 나타내는 방법으로 EZW(Enbeded Zerotree Wavelet)과 SPIHT(set partitioning in hierarchical tree)를 사용한 보다 향상된 영상 압축방법이 제안되어졌다. 특히 SPIHT는 적응 산술부호화(adaptive arithmetic coding)를 사용하지 않고도 EZW보다 뛰어난 압축률과 효과를 얻을 수 있다. 하지만 부대역(subband)간의 유사성(similarity)을 이용한 제로트리 부호화에서 계층을 나누는 일은 계수 사이의 연결관계를 깰 수 있기 때문에 간단한 일은 아니다. 본 논문에서는 SPIHT의 비트열을 여러개의 계층으로 나누고 각각의 해상도로 복원하는 새로운 정렬 방법을 제안하고, 계층간의 비트열을 균일하게 나눔으로써 보다 효율적으로 전송 할 수 있는 방법을 제안하였다. 또한 복호시에 낮은 해상도일수로 복원시간의 이득을 볼 수 있는 향상된 방법을 제안한다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.291-294
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• 2000

본 논문에서는 웨이브릿 변환영역에서 개선된 모폴로지와 적응양자화를 이용한 영상부호화 방법을 제안한다 제안한 방법은 제로트리를 기반으로 한 기존의 방법들과 유사한 코딩성능을 가지면서 EZW, SFQ 등에서 나타나는 복잡성을 모폴로지를 사용하여 유효정보를 클러스터링 함으로써 복잡성을 줄일 수 있다. 그러나 클러스터의 개수가 많아지면 클러스터를 나타내는 부가정보의 양도 많아진다. 이러한 부가정보의 비율이 실제데이터에서 많은 비중을 차지하기 때문에 개선된 모폴로지를 적용하여 효율적으로 부호화 함으로써 영상의 화질을 개선하였다. 또한 고주파 대역에서의 유효계수를 효율적으로 코딩하기 위해 적응양자화를 적용하여 양자화 시 오차범위를 줄일 수 있다. 따라서 제안한 방법은 양자화 시 발생하는 많은 비교연산을 줄일 수 있으며, 기존의 방법에 비해 화질을 개선하였다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.4
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• pp.19-28
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• 2009

This paper is a study on method that the EZW algorithm is proposed effective compression technique of wavelet transformed image. The EZW algorithm is encoded by zerotree coding technique using self-similarity of wavelet coefficients. If the coefficient is larger than the threshold a POS coded, if the coefficients is smaller than minus the threshold a NEG is coded. If the coefficient is the root of a zerotree than a ZTR is coded and finally, if the coefficient is smaller then the threshold but it is not the root of a zerotree, than an IZ is coded. This process is repeated until all the wavelet coefficients have been encoded completely. This paper was compared to EZW algorithm and a widely available version of JPEG. As the results of compare, it is shown that the PSNR of the EZW algorithm is better than JPEG.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.1057-1060
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• 2001

최근 인터넷을 통한 전자 저작물 유통이 확산됨에 따라 저작권을 보호하기 위한 디지털 워터마킹이 많이 이용되고 있다. 종래의 디지털 워터마킹 기법에서는 주로 도장 이미지를 워터마크로 사용해왔다. 본 논문은 도장 이미지가 아닌 복잡한 형태의 이미지를 삽입 할 수 있도륵 워터마크 이미지의 정보를 웨이브릿 변환을 통해 추출하여 삽입, 복원해내는 방법을 제안한다. 또한 웨이브릿 변환 계수를 제로 트리 웨이브릿 부호화 방법을 사용하여 워터마킹에 가장 적절한 계수를 선택해서 저작권 정보를 삽입하도록 한다. 이렇게 하면 적합한 대역에 워터마크를 삽입하게 되어 이미지 변형이 적고 공격에도 강인하게 된다. 이 과정에서 삽입 위치를 랜덤하게 하는 부가적인 과정을 생략할 수 있게 함으로써 효율적인 워터마크 첨가를 가능하게 하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.5
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• pp.464-473
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• 2001

Since DCT algorithm divides an image into blocks uniformly in both the spatial domain and the frequency domain, it has a weak point that it can not reflect HVS(Human Visual System) efficiently To avoid this problem, we propose a new algorithm, which combines only the merits of DCT and wavelet transform. The proposed algorithm uses the high compaction efficiency of DCT, and applies wavelet transform mode to DCT coefficients, so that the algorithm can utilize interband and intraband correlations of wavelet simultaneously After that, the proposed algorithm quantizes each coefficient based on the characteristic of each coefficient's band. In terms of coding method, the quantized coefficients of important DCT coefficients have symmetrical distribution, the bigger that value Is, the smaller occurrence probability is. Using the characteristic, we propose a new still image coding algorithm of symmetric and bidirectional tree structure with simple algorithm and fast decoding time. Comparing the proposed method with JPEG, the proposed method yields better image quality both objectively and subjectively at the same bit rate.