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디지털 영상 확대를 위한 Pseudomedian 필터의 부윈도우 설정 방법
곽노윤,권병헌,황병원,Kwak, No-Yoon,Kwon, Byong-Heon,Hwang, Byong-Won 대한전자공학회 1999 電子工學會論文誌, S Vol.s36 No.9
It is known that the digital image enlargement technique which only uses spatially neighbored pixels information in a still image can increase the size of the image but the practical enhancement of resolution is small because the frequency bandwidth of the image is basically limited. To solve this problem, this paper proposes the digital image enlargement technique that improves the reconstruction of the edge components by selectively transposing the direction of the subwindows of pseudomedian filter according to the distribution of neighbored pixels to the interpolation point. The pseudomedian filter has the better performance in aspect of the reconstruction of edge information when the pixel values masked by two subwindows parallel to the interpolation point are very similar and the pixel values masked by another subwindow that is orthogonal to the above two subwindows are similar to each other. In this paper, the computer simulation for digital image enlargement was performed with consideration of these characteristics when selecting the subwindows of pseudomedina filter. Based on this simulation result, the performance of the proposed method was analysed and its effectiveness was assessed. According to the proposed method, visual artifacts that result from using the limited samples can be effectively suppressed, and most characteristics and shapes of the original image can be preserved as well. 하나의 정지 영상 내에서 공간적으로 인접한 화소들의 정보만을 사용하여 디지털 영상을 확대하는 방법은 원영상 정보의 주파수 대역이 제한되어 있기 때문에 영상의 크기는 증가시킬 수 있으나 실질적인 해상도 향상에 대한 기여는 미비한 것으로 알려지고 있다. 이와 같은 문제를 개선하기 위해 본 논문에서는 보간 화소점에 인접한 화소들의 분포 특성에 따라 Pseudomedian 필터의 부윈도우 설정 방향을 가변적으로 전치하여 윤곽정보의 재현성을 개선한 디지털 영상 확대 방법을 제안하고 있다. 보간용 Pseudomedian 필터는 보간 화소점에 평행한 2개의 부윈도우에 의해 마스킹되는 화소값들이 서로 유사하고, 이 2개의 부윈도우와 직교하는 나머지 하나의 부윈도우에 의해 마스킹되는 화소값들이 유사할수록 윤곽 정보의 재현성이 우수해지는 특성을 갖고 있다. 따라서, 본 논문에서는 Pseudomedian 필터의 부윈도우를 설정할 시에 이와 같은 특징을 고려하여 디지털 영상 확대를 위한 컴퓨터 시뮬레이션을 수행한 후, 이 시뮬레이션 결과를 토대로 제안된 방법의 성능을 분석하고 그 타당성과 유용성을 평가하였다. 제안된 방법에 따르면, 제한된 화소 샘플을 이용함에 따른 시각적인 거부감의 초래를 효과적으로 억제할 수 있을 뿐만 아니라 원영상의 특성과 형상을 최대한 보존할 수 있다.
곽노윤(Kwak No Yoon),황병원(Hwang Byong Won) 한국정보처리학회 1999 정보처리학회논문지 Vol.6 No.8
In this paper, a variable motion estimation scheme based on HBMA(Hierarchical Block Matching Algorithm) to improve the performance and to reduce heavy computational and transmission load, is presented. The proposed algorithm is composed of four steps. First, block activity for each block is defined using the edge information of differential image between two sequential images, and then average block activity of the present image is found by taking the mean of block activity. Secondly, camera pan compensation is carried out, according to the average activity of the image, in the hierarchical pyramid structure constructed by wavelet transform. Next, the LUT classifying each block into one among Moving, No Moving, Semi-Moving Block according to the block activity compensated camera pan is obtained. Finally, as varying the block size and adaptively selecting the initial search layer and the search range referring to LUT, the proposed variable HBMA can effectively carries out fast motion estimation in the hierarchical pyramid structure. The cost function needed above-mentioned each step is only the block activity defined by the edge information of the differential image in the sequential images.
디지털 영상 확대를 위한 적응형 Pseudomedian 필터의 설계 및 성능 분석
곽노윤 ( No Yoon Kwak ),황병원 ( Byong Won Hwang ) 한국정보처리학회 2000 정보처리학회논문지 Vol.7 No.4
It is known that a digital image enlargement technique can increase the size of the image but the practical enhancement of resolution is trifle because the frequency bandwidth of the original image is basically limited. To solve this problem, this paper proposes the digital image enlargement technique which interpolates the interpolation points of honzontal and vertical direction by weighting according to the direction of edge information with the component of FOI(Filst Order Interpolation) and output of the pseudornedian hiter for image enlargement and interpolates the interpolation points of diagonal direction by selectiveIy transposing the direction of the subwindows of the pseudornedian inter accordding to the distribution of neighbored pixels thereto in the extanded image. Accordding to the proposed metheds, the digital image enlargement which preserves the characteristic of the pseudornedian filter capable of keeping the reconstruction of edge information and ref1ects the advantage of FOI can be performed. Therefore, visual artifacts could be effectively suppressed, and most characteristics and shapes of the original image call be reconstructed as well.