• Journal of the Korea Society of Computer and Information
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• v.13 no.2
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• pp.153-158
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• 2008

Blocking artefact noise is necessarily happened in compressed images using block-coded algorithms such as JPEC compressing algorithm. This noise is more recognizable especially in highly compressed images. In this paper, an algorithm is presented for reduction of blocking artefact noise using wavelet. Furthermore, we also mention about the median filter which is often used in image processing. Moreover, we compared the algorithm in this paper with the median filter, and its result was much better than the median filter both visually and numerically.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.300-303
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• 2005

본 논문에서는 디지털 멀티미디어 데이터의 저작권 보호를 위하여 웨이블릿 기반 인간 시각 시스템과 주파수 계수의 공간적 특성을 이용한 워터마킹 알고리즘을 제안하였다. 원영상을 1-Level 분해하여 HL1영역과 LH1영역을 4${\times}$4 영역으로 블록화하고 각 블록의 엔트로피와 텍스쳐 값이 가장 좋은 영역을 찾는다. 워터마크가 삽입될 영역은 상위 레벨 계수들의 상관도 특성에 따라서 3-Level 영역에 워터마크를 삽입하였다. 성능평가로 JPEG 압축, 필터링 등 워터마크된 영상에 외부공격을 가하여 워터마크 추출여부를 확인하였고, 실험결과 제안한 알고리즘은 JPEG 압축 50% 이상에서 90%이상의 상관도를 보였고, 샤프닝, 필터링 및 부분삭제 영상변형에 강인함을 보였다.

• Annual Conference of KIPS
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• 2003.11c
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• pp.1881-1884
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• 2003

본 논문은 시각적 워터마크의 삭제나 수정을 방지하기 위해 블록 기반 내용 인증(Block-wise content authentication) 방법을 제안한다. 제안한 방법은 원본 이미지와 워터마크 이미지를 사용하여 DCT 기반의 시각적 워터마크(Visible watermark)가 삽입된 이미지로 만든다. 다음, 블록 기반 서명(Block-wise signature)을 삽입하여 JPEG 과 같은 허용 가능한 이미지 조작에서는 정보가 유지되고, 워터마크의 삭제와 같은 악의적인 이미지 조작에는 인증을 허용하지 않는다. 또한 이미지의 조작된 부분을 알 수 있도록 로컬라이제이션(Localization)을 이용하여 조작된 부분의 위치를 파악한 수 있다. Lena를 포함한 여러 표준 영상을 사용하여 실험한 결과, 제안한 방법은 시각적 워터마크에 대한 다양한 공격에서 조작된 위치를 정확하게 표현할 수 있었다. 그리고 Photoshop 7.0의 Quality factor 11인 JPEG-90 압축에서 약 99%의 인증이 가능하였고, 블러링(Blurring)이나 샤프닝(Sharpening)과 같은 기타 공격에서는 각각 51%, 50%로 인증이 허용되지 않았다.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.997-999
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• 2003

The effects of JPEG2000 compression on automated DSM extraction by using the area-based matching are evaluated in this paper. The influences on DSM heights obtained via PCI Geomatics OrthoEngine module are investigated using a single stereo model of 1:5,000 scale aerial photography at image resolution of 20 ${\mu}$m. The experiment design of elevation errors are computed for a range of compression rates from 2:1 to about 100:1, and the DSM which generated from uncompressed image is used as ‘ground truth’ data for comparison. The experimental results show that the standard deviation ranged from 0.9m to 2.5m with the compression ratio from 2 to 100. It is also observed that there is no significant degradation on DSM accuracy up to the compression ratio of 33.

• Journal of Korea Multimedia Society
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• v.7 no.5
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• pp.658-667
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• 2004

For digital image compression, various fractal image coding schemes using the self-similarity of image have been studied extensively. This paper discusses the problem that occurs during the calculating process of adaptive orthogonal transformation and provides improvements of LIFS coding scheme using the transformation. This proposed scheme has a better performance than JPEG for a wide range of compression ratio. This research also proposes an image composition method consisting of all domains of the transformation. The results show that the arithmetic operation processes of the encoder and the decoder become much smaller even without the distortion of the coding performance.

• Electronics and Telecommunications Trends
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• v.34 no.6
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• pp.145-155
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• 2019

Holography is a technique that can acquire and reproduce 3D objects nearly perfectly by representing both the amplitude and phase of light. Recently, digital holography has received considerable attention because it is simpler than analog holography from acquisition to reproduction. The data size of the digital hologram increases tremendously as the quality of digital holograms depends on their pixel pitch and resolution. Hence, efficient compression is necessary to realize holographic imaging services. In this report, we introduce recent digital hologram compression techniques and JPEG Pleno holography, which is the first international standardization activity for digital hologram compression. Furthermore, we discuss the future of this field.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4557-4572
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• 2020

The Alaska competition provides an opportunity to study the practical problems of real-world steganalysis. Participants are required to solve steganalysis involving various embedding schemes, inconsistency JPEG Quality Factor and various processing pipelines. In this paper, we propose a method to ensemble multiple deep learning steganalyzers. We select SRNet and RESDET as our base models. Then we design a three-layers model ensemble network to fuse these base models and output the final prediction. By separating the three colors channels for base model training and feature replacement strategy instead of simply merging features, the performance of the model ensemble is greatly improved. The proposed method won second place in the Alaska 1 competition in the end.

• Annual Conference of KIPS
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• 2011.04a
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• pp.250-253
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• 2011

Chip manufacture nowadays turned their attention from accelerating uniprocessors to integrating multiple cores on a chip. Moreover desktop graphic hardware is now starting to support general purpose computation. Desktop users are able to use multi-core CPU and GPU as a high performance computing resources these days. However exploiting parallel computing resources are still challenging because of lack of higher programming abstraction for parallel programming. The 2-dimensional discrete cosine transform (2D-DCT) algorithms are most computational intensive part of JPEG encoding. There are many fast 2D-DCT algorithms already studied. We implemented several algorithms and estimated its runtime on multi-core CPU and GPU environments. Experiments show that data parallelism can be fully exploited on CPU and GPU architecture. We expect parallelized DCT bring performance benefit towards its applications such as JPEG and MPEG.

• ETRI Journal
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• v.44 no.1
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• pp.94-104
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• 2022

Because of its convenience and compatibility with various image processing techniques, digital image representation of holograms is generally used in digital holography, and thus, quality assessment of digital holograms is an essential issue. This study proposes a new objective quality metric for digital phase hologram image processing. The proposed metric is based on a newly defined phase distortion created by taking the 2π periodicity of phase information into account. The experimental results show that the proposed metric correlates with reconstruction image quality better than the existing metric under random distortions and also works well with JPEG 2000 compression. It is expected to be broadly used in phase image processing and compression applications including phase holograms.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.41-42
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• 2020

본 논문에서는 JPEG Pleno에서 표준 데이터세트로 제공되고 있는 디지털 홀로그램의 압축 방법을 제시한다. 디지털 홀로그램의 재현에서 시각화를 위한 랜덤 위상의 추가는 간섭현상으로 인한 스페클노이즈와 더블어 홀로그램의 압축 효율을 떨어트린다. 먼저, 다양한 웨이블릿 필터를 이용하여 홀로그램 데이터에 대한 주파수 특성 분석을 진행한다. 다음으로, 홀로그램 압축에 용이한 필터를 제안한다. 마지막으로 JPEG2000의 웨이블릿 필터인 Bi-Orthogonal (4, 4)와 제안하는 웨이블릿 필터를 이용하여 SPIHT(Set partitioning in hierarchical trees)를 이용하여 압축하고 복원하고 압축률 대비 정량적 화질평가를 통해 그 효율을 분석한다.