• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1383-1386
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• 1997

Discrete cosine transform(DCT) is the most popular block transform coding in lossy mode. DCT is close to statistically optimal transform-the Karhunen Loeve transform. In this paper, a module for DCT encoder is made with TMS320C80 based on JPEG and MPEG, which are intermational standards for image compression. the DCT encoder consists of three parts-a transformer, a vector quantizer and an entropy encoder.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.88-88
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• 2002

Satellite Image archiving system requires large storage and long transmission time. A simple and cheap way of overcoming these limitations is to increase the compression ratio. However this requires a feasibility study for accurate applications. Here, a new still image compression standard is being developed, the JPEG2000. It provides lossless and lossy compression, progressive transmission by pixel accuracy and by resolution, region-of-interest coding, user-defined tiling size, random codestream access and processing etc. In this study, we will briefly introduce the JPEG2000 compression standard which provides a new compression technique based on the wavelet technology and offers better compression ratios, and evaluate the compression ratios of JPEG2000 for satellite image by performing various image quality tests. Also, we will compare brief test result using the commercial remote sensing software.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.1-8
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• 2009

Image compression schemes, such as JPEG and JPEG2000, degrade the Quality of a reconstructed image due to their lossy characteristics. Accordingly, this paper investigates the relationship between the compression ratio and the gamut variation for a reconstructed image using JPEG and JPEG2000. To analyze the relationship between compression ratio and gamut variation, i.e. the hue and chroma shift in the uniform color space, eighteen color samples from the Macbeth ColorChecker are initially used. Based on the color shift phenomenon for the color samples, twelve natural color images, classified into two groups depending on four color attributes, are also used to investigate the relationship between the level of compression and the variation in the gamut area. As a results, through the experiments, least square method is applied to obtain the fitting curves as an equation minimizing the error between the real data and its corresponding approximated values.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.598-601
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• 2002

In this research, robustness of image watermarking mixed Key and Logo scheme was evaluated. A personal ID of a copyrighter was key and watermark was logo image. The standard images of Baboon, Cameraman and Lena were used for experimental images, binary image‘Park’of 32$\times$32 and 64$\times$64 size were used for the watermark image, respectively. for robustness evaluation of the watermark, reconstructive rates of the watermark were obtained from images inserted watermark with image transformation or JPEG lossy compression. The experimental results show that the reconstructive rates of the case of 32$\times$32 watermark was better than the case of the 64$\times$64 watermark; average 5.9%, 13.9%, 6.5%, and 4.2% in the case of scale-down rates, rotational rates, impulse noise power density, and JPEG lossy compression rates, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.1
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• pp.142-148
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• 2003

We compress medical images in order to solve problems both of request of storage mediums and of a low network speed. In this paper, integration compression environment has been developed for unity of various compression methods. Various compression methods that are implemented by integration compression environment, RLC, Lossless JPEG, and JPEG, comply with the DICOM 3.0. A compression method using DWT is implemented at it. And a unit method of Lossless compression method and lossy compression method is designed to improve images quality and to progress compression ratio. Diverse medical images can be compressed by each compression method. And integration compression environment is operated together database so that information of medical images is administered.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2292-2298
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• 2009

In this paper, the lossy image compression algorithm using the quad tree and the bandlets is proposed. The proposed algorithm transforms input images by the discrete wavelet transform (DWT) and represents the geometrical structures of high frequency bands using the bandlets with a 8 block- size. In addition, the proposed algorithm searches the position information of the significant coefficients by using the quad tree algorithm and computes the magnitude and the sign information of the significant coefficients by using the Embedded Image Coding using Zerotrees of Wavelet Coefficients (EZW) algorithm. The compression result by using the quad tree algorithm improves the PSNR performance of high frequency images up to 1 dB, compared to that of JPEG-2000 algorithm and that of S+P algorithm. The PSNR performance by using DWT and bandlets improves up to 7.5dB, compared to that by using only DWT.

• Journal of the Korea Computer Graphics Society
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• v.15 no.3
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• pp.11-18
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• 2009

In this paper, we introduce a novel method to extend the JPEG standard, which is the most widely used for lossy image compression, in order to improve compression ratio. To employ two of the most successful methodologies for the data compression: differential coding and quantization simultaneously, we propose a line-based approach. For each line in a block, we apply one-dimensional discrete cosine transformation to the increments instead of the pixel values. Those values are quantized and entropy-coded similarly to the JPEG standard. To further increase compression ratio, the proposed method is plugged into the JPEG standard to form a new compression method, in which the proposed method are applied to only selected JPEG blocks. In our experiment, we found that the proposed method outperform the JPEG standard when the qualities of the coded images are set to be high. We believe the proposed method can be simply plugged into the standard to improve its compression ratio for higher quality images.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.489-497
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• 2009

Most of existent blind watermarking methods in frequency domain use coefficient relationship to detect the watermark without original image. But the change in coefficient values occurred when the original image was attacked by lossy JPEG compression or noise addition. So robustness of watermark detection was weaken. In order to solve these problems, this paper presents a robust watermarking method, which enables multiple watermark insertion. Also, in order to reduce errors in the detected value of watermarks according to small changes in the coefficient relationship when detecting watermarks, it set the change guard value for variation of the coefficients. The experimental results show that the proposed method has good image quality and is robust to various attacks such as the JPEG lossy compression, noise addition, etc.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.381-385
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• 2006

2008년 발사를 목표로 개발되고 있는 통신해양기상위성(COMS: Communication, Ocean and Meteorological Satellite)는 기상 관측과 해양 관측 임무 및 통신 임무까지 수행하는 정지궤도 위성이다. 통신해양기상위성은 크게 탑재체와 지상국으로 나눌 수 있고 지상국은 다시 통신 임무를 위한 CTES(Communication Test Earth Station), 해양/기상 임무를 위한 IDACS(Image Acquisition and Control System), 그리고 위성 관제와 운영을 위한 SGCS(Satellite Ground Control System)로 구분된다. 이 중 IDACS의 서브시스템 중 하나인 LHGS(LRIT/HRIT Generation Subsystem)는 LRIT/HRIT(Low Rate Information Transmission/High Rate Information Transmission)를 생성하고 배포하는 기능을 가지고 있다. 관측 종료 후 LRIT/HRIT 전송 완료까지 15분 이내로 이루어져야 한다는 기상청의 요구사항을 만족하기 위해서 JPEG 압축 시간도 중요한 요소로 고려되어야 한다. 그래서 본 논문에서는 MTSAT에서 받은 LRIT/HRIT의 자료 처리를 바탕으로 lossless JPEG와 lossy JPEG의 압축 시간을 측정하여 압축률을 비교하여 성능 분석을 해보기로 한다. 이렇게 도출해낸 수치자료는 COMS LHGS 설계에 활용할 수 있다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.11
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• pp.97-104
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• 2004

This paper proposes an efficient VLSI architecture of 9-7/5-3 Lifting DWT filters that is used by lossy or lossless compression of JPEG2000. The proposed architecture uses only internal line memories to compute Lifting-DWT operations and its PE(Processing Element) has critical path with 1 multiplier and 1 adder. To reduce the number of PE, we make the vertical filter that is responsible for the column operations of the first level perform both the row and column operations of the second and following levels. As a result, the architecture has smaller hardware cost compared to that of other architectures. It was modeled in RTL level using VHDL and implemented on Altera APEX 20K FPGA.