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신용달,이봉락,이건일 한국통신학회 1993 韓國通信學會論文誌 Vol.18 No.10
본 논문에서는 경사도 및 새로운 초기값을 이용한 적응 BTC를 제안하였다. 에지부분에서 발생되는 톱니 모양의 문제점을 줄이기 위해 구획의 등급을 결정하는 새로운 계수로서 sobel 연산자의 경사도를 이용하였다. 에지를 포함한 복잡한 영역에서 선택되는 4 레벨 양자화에서 발생되는 심한 양자화 오차를 줄이기 위해서 새로운 초기값을 정의하였다. 컴퓨터 모의실험을 통하여 제안방법이 기존의 적응 BTC보다 계산량이 간단하며, 에지 부분에서 톱니모양의 결점이 감소되었으며, 또한 PSNR이 개선됨을 확인하였다. We proposed an adaptive block truncation coding(BTC) using gradient and a new initial value. We used gradient of sobel operator as a new category classification coefficient to reduce Jagged appearance at edge part. We defined a new initial value to reduce large quantization error in the 4-level quantizer block including edge part. By computer simulations, we showed that the proposed method less computation load, reduced jagged appearance at edge part, also improved PSNR more than the conventional adaptive BTC.
신용달,김영춘,권성근 永同大學校 2001 硏究論叢 Vol.7 No.1
본 논문에서는 비가시성을 개선시키기 위하여 새로운 워터마크를 삽입 방법을 제안하였다. 기존의 워터마킹 알고리듬에서 기본적으로 워터마크를 삽입하는 방법은 1+αi xi 같은 1차 방정식의 형태로 사용하였으나, 제안한 방법에서는 1+bxi+αxi2형태인 2차 방정식으로 확장하였다. 제안한 알고리듬과 기존의 알고리듬에 대한 성능을 평가하기 위해서 LENA, GOLDHILL, BARBARA, 및 MAN 영상을 사용하여 컴퓨터 모의실험을 행하였다. 모의실험 결과 정규화 된 유사도가 100 %일 때 원 영상과 워터마크가 삽입된 영상과의 PSNR을 비교한 결과 제안한 방법이 기존의 방법들 보다 모든 영상에서 비가시성이 매우 우수함을 확인할 수 있었다. We present digital watermarking using a new embedding watermark in order to improve the invisibility. Generally, embedding watermark used first equation form as 1+ αi xi but we extended second equation form as 1+ bxi+αxi2 in this paper. We performed a computer simulation in order to compare proposed method to other methods using LENA, GOLDHILL, BARBARA, and MAN images. In computer experiments, the proposed watermark algorithm was found to be more invisible than the conventional algorithms at 100% normalized similarity.
신용달,이봉락,이건일 대한전자공학회 1993 전자공학회논문지-B Vol.b30 No.12
An adaptive block truncation coding(BTC) using human visual system(HVS) is proposed. To reduce visible blocking effect at sensitive area in HVS. a new category classification coefficient is proposed. The categroy classification coefficient was derived by combining the modified HVS and standard deviation. By computer simulations, we showed that the proposed method reduced blocking effect at low bit rate coding more than the conventional Hui's method.
Fast Detection of Copy Move Image using Four Step Search Algorithm
신용달,조용석 한국멀티미디어학회 2018 멀티미디어학회논문지 Vol.21 No.3
We proposed a fast detection of copy-move image forgery using four step search algorithm in the spatial domain. In the four-step search algorithm, the search area is 21 (-10∼+10), and the number of pixels to be scanned is 33. Our algorithm reduced computational complexity more than conventional copy move image forgery methods. The proposed method reduced 92.34 % of computational complexity compare to exhaustive search algorithm.
Fast Detection of Copy-Move Forgery Image using DCT
신용달 한국멀티미디어학회 2013 멀티미디어학회논문지 Vol.16 No.4
In this paper, we proposed a fast detection method of copy-move forgery image based on low frequency coefficients of the DCT coefficients. We proposed a new matching criterion of copy-moved forgery image detection (MCD) using discrete cosine transform. For each 8×8 pixel block, the DCT transform is calculated. Our algorithm uses low frequency four (DC, 3 AC coefficient) and six coefficients (DC, 5 AC coefficients) of DCT per 8×8 pixel block. Our algorithm worked block matching for DCT coefficients of the 8×8 pixel block is slid by one pixel along the image from the upper left corner to the lower right corner. Our algorithm can reduce computational complexity more than conventional copy moved forgery detection algorithms.
Fast Detection of Forgery Image using Discrete Cosine Transform Four Step Search Algorithm
신용달,조용석 한국멀티미디어학회 2019 멀티미디어학회논문지 Vol.22 No.5
Recently, Photo editing softwares such as digital cameras, Paintshop Pro, and Photoshop digital can create counterfeit images easily. Various techniques for detection of tamper images or forgery images have been proposed in the literature. A form of digital forgery is copy-move image forgery. Copy-move is one of the forgeries and is used wherever you need to cover a part of the image to add or remove information. Copy-move image forgery refers to copying a specific area of an image itself and pasting it into another area of the same image. The purpose of copy-move image forgery detection is to detect the same or very similar region image within the original image. In this paper, we proposed fast detection of forgery image using four step search based on discrete cosine transform and a four step search algorithm using discrete cosine transform (FSSDCT). The computational complexity of our algorithm reduced 34.23 % than conventional DCT three step search algorithm (DCTTSS).
움직임 벡터 분포 특성을 이용한 고속 적응 블럭 정합 알고리즘
신용달,김영춘,Shin, Yong-Dal,Kim, Young-Choon 대한전자공학회 1998 電子工學會論文誌, S Vol.s35 No.12
We present a fast adaptive block matching algorithm using characteristic of the motion vector distribution. In the presented method, the block is classified into one of four motion categories: stationary block, quasi-stationary block, medium-motion block or high-motion block according to characteristic of the MAD(0,0) distribution for motion vector, each block estiamtes the motion vector adaptively. By the simulation, the PSNR of our algorithm is similar to NTSS method. The computation amount of the presented method decreased 30.44% ~ 40.27% more than NTSS method. 본 논문에서는 움직임 벡터의 분포특성을 이용한 고속 적응 블럭 정합 알고리즘을 제안하였다. 제안 방법에서는 움직임 벡터에 따른 MAD(0,0)의 분포특성을 분석하여 블럭을 움직임이 없는 블럭, 작은 블럭, 중간정도인 블럭 혹은 큰 블럭으로 분류한 후 각 블럭의 특성에 따라 적응적으로 움직임 벡터를 추정한다. 제안한 방법의 성능을 평가하기 위해서 컴퓨터 시뮬레이션을 수행하였다. 이 결과로부터 제안 방법의 PSNR은 기존의 NTSS 방법과 거의 비슷하면서도 계산량이 30.44% ~ 40.27% 감소되는 효과적인 방법임을 확인할 수 있었다.
움직임 벡터 추정을 위한 고속 적응 블럭 정합 알고리즘
신용달,이승진,김경규,정원식,김영춘,이봉락,장종국,이건일 대한전자공학회 1997 電子工學會論文誌, S Vol.s34 No.9
We present a fast adaptive block matching algorithm using variable search area and subsampling to estimate motion vector more exactly. In the presented method, the block is classified into one of three motion categories: zero motion vector block, medium-motion bolck or high-motion block according to mean absolute difference of the block. By the simulation, the computation amount of the presented methoe comparable to three step search algorithm and new three step search algorithm. In the fast image sequence, the PSNR of our algorithm increased more than TSS and NTSS, because our algorithm estimated motion vector more accurately.