• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.603-610
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• 2008

In this paper, we propose an efficient noise reduction algorithm for digital hologram during acquisition and transmission. The proposed algorithm segment a digital hologram with object region and background region after DCT. Then, we adopt a histogram transition method for object region and zero-value change method for background region. The experimental results show that our algorithm has beuer performance than a natural image denoising algorithm.

• Journal of Broadcast Engineering
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• v.8 no.1
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• pp.30-36
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• 2003

According to an evolution of image and video compression technologies, most digital images are in the compressed form. Resizing of these compressed images have various applications such as transmission of resized image according to varying bandwidth, content adaptation for display purpose and etc. Discrete Cosine Transform (DCT) is the most popular transformation for image compression. Recently, several researches have been performed to obtain the reconstructed image of original size in the DCT domain after downsampling and upsampling in the DCT domain. Main focus of these researches is to improve quality of the reconstructed image after downsampling and upsampling in the DCT domain In this paper, we present an modified IDCT method to downsize DCT-encoded image. Furthermore, we propose an efficient scheme for image downsampling and upsampling in the DCT domain With these modified IDCT method. The proposed scheme Provides higher PSNR values than the existing schemes In terms of the reconstructed image after halving and doubling in the DCT domain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.4
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• pp.309-324
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• 1987

In recent years has been an increasing interest with respect to using the discrete cosine transform(DCT) of which performance is found close to that of the Karhumen-Loeve transform, known to be optimal in the area of digital image processing for tha purpose of the image data compression. Among most of reported algorithms aimed at lowering the coputation complexity. Chen's algorithm is is found to be most popular, Recently, Lee proposed a now algorithm of which the computational complexity is lower than that of Chen's. but its performance is significantly degraded by FWL(Finite-Word-Lenght) effects as a result of employinga a fixed-poing arithmetic. In this paper performance evaluation of these two algorithms and error analysis of FWL effect are described. Also a scaling technique which we call Up & Down-scaling is proposed to allevaiate a performance degradation due to fixed-point arithmetic. When the 16x16point 2DCT is applied on image data and a 16-bit fixed-point arithmetic is employed, both the analysis and simulation show that is colse to that of Chen's.

• Journal of KIISE
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• v.42 no.2
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• pp.162-168
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• 2015

Image data is mostly stored in compressed form because of its huge size. Therefore, a series of cumbersome procedures is required to apply a transformation to image data: decompression, extraction of spatial data, transformation and recompression. In this paper, we employ DCT(Discrete Cosine Transform) coefficients to change the spatial presentation of images. DCT is commonly used in still image compression standards such as JPEG and moving picture compression standards such as MPEG-2, MPEG-4, and H.264. In this paper, we derived mathematically the relationship between the geometry transformation in the spatial domain and coefficient changes in the DCT domain and verified it with images in the JPEG file format. Because of the efficiency of transformation in the frequency domain, our findings can be utilized for light-weight partial image encryption for privacy data protection or entertainment contents protection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.679-684
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• 1994

Progressive transmission using optimum bit-ordering of discrete cosine transform(DCT) coded image is proposed to reconstruct a better image in a few bits among all the coded bits at the receiver. It is to transmit the bit gradually to reduce the distrotion of the reconstructed image most by transmitting one more bit. To do this, the power transfer factor(PTF) which is the squared value of difference between the reconstruction level of embedded quantizer and another reconstruction level made by transmitting one more bit is defined. And then, the transmission order of bits is obtained by sorting the PTFs of the coded bits. As a results, the proposed method can reconstruct image having less distortion and better quality at the same bit rate than the conventional zig-zag scan.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.813-816
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• 2018

X-ray 진단에서 그리드 하드웨어의 사용은 산란선에 의한 영상의 왜곡을 보정할 수 있는 장점이 있는 반면, 반복되는 라인 형태의 그리드 아티팩트를 발생시키는 부작용을 수반한다. 본 논문에서는 이러한 그리드 라인을 제거하는 방법론으로서 이산코사인변환(DCT: discrete cosine transform)을 사용 하는 기법을 제안한다. X-ray 영상에서 그리드 라인의 특성은 피사체의 형태와 영상의 영역에 따라 서로 다른 특성을 갖는다. 이에 본 연구에서는 동적으로 재구성되는 분할 구조를 기반으로 DCT 변환을 적용하고 개별 영역별로 필터전달함수를 최적화하는 방법을 채택하였다. 추출된 주파수 영역 데이터에 대하여 그리드 라인의 대역을 검출하는 알고리즘을 제안하였으며, 필터전달함수로 Kaiser윈도우와 Butterworth 필터를 조합한 형태의 밴드스톱필러(BSF: band stop filter)를 구현하였다. 또한 블로킹 현상을 개선하기 위하여 다중 영상으로부터 경계선 부분의 픽셀값을 결정하는 방법론을 제안하였다. 제안된 이론에 대하여 실제 영상을 사용한 실험결과로부터 그 타당성을 평가하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.17-22
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• 2014

Watermarking is one of the methods that insist on a copyright as it append digital signals in digital informations like still mobile image, video, other informations. This paper proposed an improved DCT-based watermarking scheme using quantized coefficients of image. This process makes quantized coefficients through a Discrete Cosine Transform and Quantization. The watermark is embedded into the quantization coefficients in accordance with location(key). The quantized watermarked coefficients are converted to watermarked image through the inverse quantization and inverse DCT. Watermark extract process only use watermarked image and location(key). In watermark extract process, quantized coefficients is obtained from watermarked image through a DCT and quantization process. The quantized coefficients select coefficients using location(key). We perform it using inverse DCT and get the watermark'. Simulation results are satisfied with high quality of image (PSNR) and Normalized Correlation(NC) from the watermarked image and the extracted watermark.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.6
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• pp.585-590
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• 2002

In the typical data partitioning for error-resilient video coding, motion and macroblock header information is separated from the texture information. It can be an effective tool for the transmission of video over the error prone environment. For Intra-coded frames, however, the loss of DCT (discrete cosine transform) coefficients is fatal because there is no ther information to reconstruct the corrupted macroblocks by errors. For Inter-coded frames, when error occurs in DCT coefficients, the picture quality is degraded because all DCT coefficients are discarded in those packets. In this paper, we propose an efficient data partitioning and coding method for DCT-based error-resilient video. The quantized DCT coefficients are partitioned into the even-value approximation and the remainder parts. It is shown that the proposed algorithm provides a better quality of the high priority part than the conventional methods.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.6
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• pp.55-62
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• 2005

This paper proposes a method to recognize a face using DCT/LDA where LDA is applied to DCT coefficients of an input face image. In the proposed method, SSS problem of LDA due to less number of training data than the size of feature space can be avoided by expressing an input image in low dimensional space using DCT coefficients. In terms of the recognition rate, both the proposed method and the PCA/LDA method have shown almost equal performance while the training time of the proposed method is much shorter than the other. This is because DCT has the fixed number of basis vectors while the property of energy compaction rate is similar to that of PCA. Although depending on the number of coefficients employed for the recognition, the experimental results show that the performance of the proposed method in terms of recognition rate is very comparable to PCA/LDA method and other DCT/LDA methods, and it can be trained 13,000 times faster than PCA/LDA method.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.1-9
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• 2010

In this paper, we propose an efficient compression method of the integral images. The integral imaging is a well-known technique to represent and record three-dimensional images. The proposed method is based on three dimensional discrete cosine transform (3D-DCT). The 3D-DCT techniques for the integral images have been reported as an efficient coding method for the integral images which reduces the redundancies between adjacent elemental images. The proposed method is a compression method efficient to integral images using adaptive block mode(ABM), based on the 3D-DCT technique. In the ABM, 3D-DCT blocks adaptive to the characteristics of integral images are constructed, which produces variable block size 3D-DCT blocks, and then 3D-DCTs for the 3D blocks are performed. Experimental results show that the proposed method gives significant improvement in coding efficiency. Especially, at the high bit-rates, the proposed method is more excellent since the overhead incurred by the proposed method take less part of the total bits.