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도트 패턴 데이터베이스를 이용한 모델 기반 칼라 영상 중간조 처리 방법
이채수,박양우,장주석 경운대학교 산업기술연구소 1999 産業技術硏究論文誌 Vol.2 No.1
Model-based color image halftoning method using dot-pattern databases is proposed for low-resolution color image halftoning. The proposed algorithm has benefits of simple processing, less computational time of the ordered dither and benefits of aperiodic, uncorrelated structure without low-frequency graininess of the blue noise masking. The dot-pattern is defined as a part divided from a dot-profile, which is the binary pattern resulting from the halftoning of a constant gray level. In halftoning procedure, in order to improve the visual quality of the color halftoning, contrast sensitivity function (CSF) of human visual system is used. Using this CSF, the visual difference between original image and halftoned image can be computed as numerical value. Therefore, optimal dot-pattern can be selected from the database.
연속계조 칼라재현을 위한 가변 다중 닻점을 이용한 색역 사상
이채수,이철희,하영호,Lee, Chae-Su,Lee, Cheol-Hui,Ha, Yeong-Ho 대한전자공학회 1999 電子工學會論文誌, S Vol.s36 No.8
In this paper, new gamut-mapping algorithm (GMA) that utilizes variable anchor points (center of gravity on the luminance axis) is proposed. The proposed algorithm increases luminance range, which is reduced from conventional gamut mapping toward an anchor point. In this process, this algorithm utilizes multiple anchor points with constant slopes to both reduce a sudden color change on the gamut boundary of the printer and to maintain a uniform color change during the mapping process. Accordingly, the proposed algorithm can reproduce high quality images with low-cost color devices. 본 논문에서는 가변하는 다중 닻점을 이용하는 새로운 색역 사상 방법을 제안한다. 제안된 방법은 기존의 한 개의 닻점을 사용하는 색역 사상에서 발생하는 휘도 범위의 축소를 가변하는 닻점을 이용하여 보상하여준다. 또한 이 과정에서 연속 계조 칼라를 재현하기 위하여 색역을 여러 영역으로 구분하여 각각의 영역에서 다른 닻점을 사용하는 다중 닻점 방식을 제안한다. 따라서 본 논문에서는 저가의 칼라 출력장치에서 고화질의 칼라를 재현할 수 있게 한다.
이채수,장주석 경운대학교 산업기술연구소 2001 産業技術硏究論文誌 Vol.3 No.2(C)
Recently many devices print electronic images in a variety of ways. The reproduced color, however, is different from the original color because of the difference of hardware characteristics. To maintain device independent color, gamut mapping method is proposed. The proposed color gamut mapping uses nonlinear intensity mapping and clipping for saturation mapping on HSI color space. In the dithering operation, expanded nonlinear ordered dithering and modified error diffusion are proposed. The proposed ordered dithering uses expanded nonlinear quantization which considers overlapping phenomena of neighbored printing dots. In the modified error diffusion, quantization error to be diffused are adjusted to improve both image blur and color change produced in the error diffusion. So, the printed image is similar to the image of monitor. Our results indicate that proposed algorithm can produce high quality image in the low bit color devices.
칼라 프린팅을 위한 비선형적 양자화 및 변형된 점 확산 방법
이채수,김경만,이응주,박양우,하영호 대한전자공학회 1996 전자공학회논문지-B Vol.b33 No.3
Recently, the use of color data is growing fast in the area of image processing. To represent full resolution image on a limited output device, image has to be quantized an dithered. So, many dithering techniques are foundd in the printing. In this paper, we propose nonlinear quantization to consider the overlapping phenomena of neighboring printing dots and modified dot diffusion algorithm to compensate the color degradation produced in the quantization process. In the modified dot-diffusion quantization errors to be diffused are adjusted to improve both image blur and color change produced in the dot diffusion. The printed image obtained by the proposed color dithering method has higher visual quality an less color degradation than the images by conventional printing method.
이채수,김경만,이철희,하영호,Lee, Chae-Soo,Kim, Kyeong-Man,Lee, Cheol-Hee,Ha, Yeong-Ho 대한전자공학회 1998 電子工學會論文誌, S Vol.s35 No.6
최근에 영상 처리 시스템에서 칼라 데이타의 사용이 급격히 증가하고 있다. 그러나 색 재현 능력의 차이가 있고 각 장치마다 고유의 색좌표계를 사용하므로 서로 다른 장치사이에서 색 재현시에는 좌표계 변환이 요구된다. 특히 색재현 범위가 좁은 프린터에서 자연색을 출력하기 위해서는 색역 사상과 주어진 색역 계조의 범위를 확장할 수 있는 디더링 과정이 필요하다. 본 논문에서는 색역 사상을 위하여 각 장비의 출력 특성을 고려한 비선형 사상 함수를 획득하여 이를 기반으로 하여 장비들간의 색역 일치를 이루었다. 디더링 과정에서는 채색시 발생하는 중복 면적의 특성을 고려하여 양자화 단계를 확장하는 비선형 순서 디더링과 오차 확산 방법에서 발생하는 경계 부분의 문드러짐과 인접색의 변형을 줄일 수 있는 변형된 오차 확산 방법을 제안한다. Recently many devices print electronic images in a variety of ways. The reproduced color, however, is different from the original color because of the difference of hardware characteristics. To maintain device independent color, gamut mapping method is proposed. The proposed color gamut mapping uses nonlinear intensity mapping and clipping for saturation mapping on HSI color space. In the dithering operation, expanded nonlinear ordered dithering and modified error diffusion are proposed. The proposed ordered dithering uses expanded nonlinear quantization which considers overlapping phenomena of neighbored printing dots. In the modified error diffusion, quantization errors to be diffused are adjusted to improve both image blur and color change produced in the error diffusion. So, the printed image is similar to the image of monitor. Our results indicate that proposed algorithm can produce high quality image in the low bit color devices.
휘도값에 가변하는 닻점을 이용한 영상 의존 색역 사상 방법
이채수,박양우 경운대학교 산업기술연구소 2002 産業技術硏究論文誌 Vol.5 No.1(B)
Currently many devices reproduce electronic images in the various ways. However the color that is reproduced in any device is different from the original color due to the differences in the gamut between devices. In this paper, an image dependent gamut mapping method is proposed. This method clips the chroma with compensating for the change of lightness caused by the lightness scaling. The anchor point, which is the center point in the mapping, is set as a lower point by the proposed method than a point by the conventional mapping method. This reduces the color difference between the original image on the monitor and the results on the printer after mapping toward this anchor point. In addition, to heighten the color contrast on the constant hue, the different two mapping methods are applied to the printer gamut which is divided in two regions, bright region and dark region. Consequently, the printer output image was highly consistent with the corresponding monitor image.
이채수,박양우 경운대학교 산업기술연구소 2000 産業技術硏究論文誌 Vol.3 No.1(B)
In this paper, new gamut-mapping algorithm (GMA) that utilizes variable anchor points (center of gravity on the luminance axis) is proposed. The proposed algorithm increases luminance range, which is reduced from conventional gamut mapping toward an anchor point. In this process, this algorithm utilizes multiple anchor point with constant slopes to both reduce a sudden color change on the gamut boundary of the printer and to maintain a uniform color change during the mapping process. Accordingly, the proposed algorithm can reproduce high quality images with low-cost color devices.
이채수(Lee Chae Soo),최영준(Choi Young Jun),김현기(Kim Hyun Gee),양옥철(Yang Ok Chul),정재헌(Chong Chae Hon) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The once-through heat recovery steam generator is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of boiler is structurally simpler than drum type boiler. In drum type boiler, each tube play a well-defined role: water preheating, vaporization, superheating. Empirical equations are available to predict the average heat transfer coefficient for each regime. For once-through heat recovery steam generator, this is no more the case and mathematical models have to be adapted to account for the disappearance of drum type economizer, boiler, superheater. General equations have to be used for each tube of boiler, and actual heat transfer condition in each tube has to be identified.