• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.6
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• pp.561-566
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• 2019

In the Internet space, integrity and security must be maintained for secure and confidential communication, which ensures reliability between sender and receiver. Cryptography is an important factor in maintaining robustness against external attacks. For this purpose, encryption and steganography methods are used. Steganography is a method of hiding confidential information without making statistically significant changes to digital media. I propose a method of transforming the Hangul-Jamo consisting of choseong, jungseong and jongseong, and inserting them into RGB pixel values of the cover image. In order to improve security, a new blending method was used to hide the altered information in the lowest region. In this case, a mixture of LSB and LDR techniques was applied. PSNR was calculated for image quality. The PSNR of the proposed method is 43.225dB, which satisfies the lowest level.

• Journal of Korea Multimedia Society
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• v.15 no.8
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• pp.977-985
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• 2012

The purpose of this study was to present a non-photorealistic rendering technique that is efficient in single images and moving images. In case of single images, they could be processed in a real-time base by realizing flow-based DoG filter and bilateral filter, which have been frequently used in the single image NPR technique recently, in the CUDA environment. In case of moving images, the investigator presented not the existing method of NPR moving images which generating images by applying the single image NPR technique to every frame, but the method of using the single image NPR technique in the first frame and stylizing it, and then of using the motion vector-based pixel mapping in the second frame on and copying the bright values of pixels that move on the frame into the location of next frame's motion vector, thus reducing unnecessary volume of calculation and maintaining the consistency between frames. In this study, the performance of this method was proved via an experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.5
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• pp.390-399
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• 1988

A conventional BTC has the merit of real time processing and simple computation, but has the problem that its compression rate is low. In this paper, a modified BTC using the Quad Tree which is frequently used in binary image is proposed. The method results in the low compression rate by decreasing the total number of subblocks by mean of making the size of a subblock large in the small variation area of graty level and the size af a subblock small in the large variation area of gary level. For the effective transmission of bit plane, the Huffman run-lengh code for the large size of a subblock and the lookup table for tha small size of a subblock are used. The proposed BTC method show the result of coding 256 level image at the average data rate of about 0.8 bit/pixel.

• The Journal of Korean Physical Therapy
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• v.24 no.2
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• pp.66-72
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• 2012

Purpose: The purpose of this study is to explore the importance of the image distortion correction in the cross sectional area measurement for the iliopsas muscle, tensor fasciae latae muscle, gluteus maximus muscle and the knee extensor muscles, by using (magnetic resonance imaging) MRI. Methods: This study was performed using an open 0.32T MRI system. To estimate the image distortion, T1 images for an AAPM homogeneity/linearity phantom were acquired, and the region in which the maximum geometric distortion was less than or equal to the pixel size (1.6 mm) of the images, it was defined as the distortion correction-free region. The T2 images for a human subject's pelvis and thigh in normal positions were obtained. Then, after the regions of interest in the pelvis and thigh were moved into the distortion correction-free region, T2 images for the pelvis and thigh were scanned with the same imaging parameters used in the previous T2 imaging. The cross-sectional areas were measured in the two T2 images that were obtained in the normal position, and the distortion correction-free region, as well as the area error caused by geometric image distortion was calculated. Results: The geometrical distortion is gradually increased, from the magnet center to the outer region, in axial and coronal plane. The cross-sectional area error of gluteus maximus muscle and the knee extensors was as high as 9.27% and 3.16% in before and after distortion correction, respectively. Conclusion: The cross-sectional area of the muscles that suffered from the geometrical distortion is necessary to correct for the estimation of the intervention.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.631-636
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• 2016

Hitherto, spatial resolution has commonly been evaluated by test patterns or phantoms built on some specific distances (from close to far) between two objects (or double targets). This evaluation method's shortcoming is that resolution is restricted to target distances of phantoms made for test. Therefore, in order to solve the problem, this study proposes and verifies a new method to efficiently test spatial resolution with a single target. For the research I used PSF and JND to propose an idea to measure spatial resolution. After that, I made experiments by commonly used phantoms to verify my new evaluation hypothesis inferred from the above method. To analyse the hypothesis, I used LabVIEW program and got a line pixel from digital image. The result was identical to my spatial-resolution hypothesis inferred from a single target. The findings of the experiment proves only a single target can be enough to relatively evaluate spatial resolution on a digital image. In other words, the limit of the traditional spatial-resolution evaluation method, based on double targets, can be overcome by my new evaluation one using a single target.

• The Korean Journal of Applied Statistics
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• v.33 no.5
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• pp.603-614
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• 2020

This study focuses on the prediction and factors of apartment prices in Seoul using a convolutional neural networks (CNN) model that has shown excellent performance as a predictive model of image data. To do this, we consider natural environmental factors, infrastructure factors, and social economic factors of the apartments as input variables of the CNN model. The natural environmental factors include rivers, green areas, and altitudes of apartments. The infrastructure factors have bus stops, subway stations, commercial districts, schools, and the social economic factors are the number of jobs and criminal rates, etc. We predict apartment prices and interpret the factors for the prices by converting the values of these input variables to play the same role as pixel values of image channels for the input layer in the CNN model. In addition, the CNN model used in this study takes into account the spatial characteristics of each apartment by describing the natural environmental and infrastructure factors variables as binary images centered on each apartment in each input layer.

• Journal of the Korean Society of Radiology
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• v.9 no.6
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• pp.403-408
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• 2015

Hard X-ray has been widely used in medical and industrial fields because it can be applied to observe the inside of a sample. Computed tomography provides sectional images of the sample through the reconstruction of the projection images. The quality of sectional images strongly depends on that of projection images. Ring artifact appeared on the seconal image can be made by the abnormal pixels of the detector used. In this study, we examine the ring artifact ratio in the circle phantom as a function of detection error of the detector used in computed tomography. The ring artifact increased with the increment of detection error under parallel and fan beam geometries and strongly increased near the center of rotation. The corrections, dead pixel and flat field corrections, for the images taken with the detector are required before the image reconstruction process to reduce the ring artifact in the computed tomography.

• Journal of KIISE
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• v.43 no.8
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• pp.835-840
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• 2016

Monte Carlo ray tracing has been widely used for simulating a diverse set of photo-realistic effects. However, this technique typically produces noise when insufficient numbers of samples are used. As the number of samples allocated per pixel is increased, the rendered images converge. However, this approach of generating sufficient numbers of samples, requires prohibitive rendering time. To solve this problem, image filtering can be applied to rendered images, by filtering the noisy image rendered using low sample counts and acquiring smoothed images, instead of naively generating additional rays. In this paper, we proposed a Stein's Unbiased Risk Estimator (SURE) based $\grave{A}$-Trous wavelet to filter the noise in rendered images in a near-interactive rate. Based on SURE, we can estimate filtering errors associated with $\grave{A}$-Trous wavelet, and identify wavelet coefficients reducing filtering errors. Our approach showed improvement, up to 6:1, over the original $\grave{A}$-Trous filter on various regions in the image, while maintaining a minor computational overhead. We have integrated our propsed filtering method with the recent interactive ray tracing system, Embree, and demonstrated its benefits.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.18 no.3
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• pp.315-322
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• 2000

DSM(Digital Surface Model) is a digital model which represents the surface elevation of a region. DSM is necessary for orthoimage generation, and frequently used in man-made object extraction from aerial photographs nowadays. Image matching technique enables automatic DSM generation. This proposed a image matching method which can be applied to automatic generation of DSM for Built-up Area. The matching method proposed is to find conjugate points and conjugate lines from overlapping aerial images. In detecting conjugate points, the positional relation between possible conjugate point pair as well as correlation of pixel gray value is compared. In detecting conjugate lines, the color attribute of flank region of line, shape of line, positional relation between neighborhood points and lines, and the connection relation between lines are compared. The proposed matching method is assumed to be useful for DSM generation including Built-up Area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.406-414
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• 2005

The necessity for a technique to protect intellectual property of a digital content has been increasing, especially for the image/video contents which are the most favorite because of their high information-intensive property. According to this demand, this paper proposed a digital watermarking algorithm, which is recognized as the most promising technique. This algorithm targets MPEG compression system and the watermarking process is to be performed during the compression process. It inserts watermark only in Y components of I-frames. Experimental results showed that the proposed method satisfied both imperceptibility and robustness against various attacks. The PSNR difference between the compressed images(the average compression ratio was about 27:1 with Y:Cb:Cr=4:2:0 color format for TM5-based compression) with and without watermarking was only 1.8dB ($4.2\%$). In each case that the resulting image after an attack was reusable the normalized correlation between the extracted watermark and the original one was above 0.8.