재보간의 특성을 이용한 디지털 이미지의 합성 영역 및 필터링 영역 검출

황민구(Min-Gu Hwang),하동환(Dong-Hwan Har) 한국멀티미디어학회 2012 멀티미디어학회논문지 Vol.15 No.2

디지털 카메라의 렌즈 왜곡 보정에 사용된 보간 패턴 추출을 통한 카메라 식별 방법

황민구 ( Min-gu Hwang ),김동민 ( Dong-min Kim ),하동환 ( Dong-hwan Har ) 한국인터넷정보학회 2012 인터넷정보학회논문지 Vol.13 No.3

촬영된 카메라의 기초 정보를 담고 있는 EXIF 파일을 편집 프로그램들을 통해 삭제 또는 변형하게 되어 우리 주변에서 출처를 알 수 없는 이미지들이 상당수 존재하게 되었다. 이와 같은 문제점은 디지털 이미지의 출처를 왜곡하여 공공기관에서 사건의 분석 및 감정에 혼선을 줄 수 있다. 특히 증거의 출처를 명시하는 법정 기관에 출처가 삭제, 변형된 EXIF 파일을 가진 디지털 사진은 객관적 증거의 역할을 할 수 없다. 본 논문은 이와 같은 문제를 해결하기 위한 연구로써 촬영에 사용된 카메라의 신원을 추적하는 데 목적이 있다. 이를 위해 본 논문은 디지털카메라 이미지 프로세싱에서 사용하는 렌즈 왜곡 보정 알고리즘을 주목하였다. 렌즈 왜곡 보정은 맵핑 알고리즘을 이용하며 이 때 위신호 인공물(Aliasing artifact)와 복원 인공물(Reconstruction artifact)의 발생을 제거하기 위한 보간 알고리즘을 사용한다. 여기서 보간은 맵핑의 패턴과 유사한 형태로 나타나며 이 보간의 흔적을 찾는 것이 연구의 핵심이다. 본 논문에서는 맵핑에 사용된 보간 패턴을 검출하기 위해 미니멈 필터(Minimum Filter)를 이용한 검출 알고리즘을 제안하였다. 보간이 발생한 영역과 그렇지 않은 영역을 분류하여 두 영역에 동일한 미니멈 필터를 적용한다. 이를 DFT를 통해 각 영역 간의 주파수 특성이 어떻게 나타나는지 확인하였다. 이 결과를 바탕으로 두 영역간의 차분값을 활용하여 최종 검출 맵으로 구현하였다. Throughout developing digital technology, reproduction of image is growing better day by day. And at the same time, diverse image editing softwares are developed to manage images easily. In the process of editing images, those programs could delete or modify EXIF files which have the original image information; therefore images without the origin source are widely spread on the web site after editing. This matter could affect analysis of images due to the distortion of originality. Especially in the court of law, the source of evidence should be expressed clearly; therefore digital image EXIF file without deletion or distortion could not be the objective evidence. In this research, we try to trace the identification of a digital camera in order to solve digital images originality, and also we focus on lens distortion correction algorism which is used in digital image processing. Lens distortion correction uses mapping algorism, and at this moment it also uses interpolation algorism to prevent aliasing artifact and reconstruction artifact. At this point interpolation shows the similar mapping pattern; therefore we want to find out the interpolation evidence. We propose a minimum filter algorism in order to detect interpolation pattern and adjust the same minimum filter coefficient in two areas; one has interpolation and the second has no interpolation. Throughout DFT, we confirm frequency character between each area. Based on this result, we make the final detection map by using differences between two areas. In other words, thereby the area which has the interpolation caused by mapping is adjusted using minimum filter for detection algorism; the second area which has no interpolation tends to different frequency character.

디지털 사진 내의 피사체 소실점을 이용한 렌즈 화각 측정 연구

황민구 ( Min Gu Hwang ),김동민 ( Dong Min Kim ),하동환 ( Dong Hwan Har ) 한국사진학회 2010 AURA Vol.0 No.22

As the tool to represent plane images, photos have the different vanishing point from an observer`s direction. However, size and shape of the object are changed due to angel and distortion of the optical lens, which changes the location of vanishing point. Due to that reason, if the vanishing point of the object is accurately measured, it in turn measures lens angle. Therefore, this study considered optical principals and geometric elements of the lens, and analyzed the location of vanishing point through 3D model about the specific objet in the photo. In addition, it measured lens angle used to actual digital photographing by applying lens angle values from the focal distance based on 35mm film. Like this, if the completed measuring method is applied, lens angle of the digital photos can be found out without metadata.

영상의 기초정보 추출을 위한 렌즈 화각 및 피사체 거리 측정 연구

황민구(Min-Gu Hwang),하동환(Dong-Hwan Har) 대한전자공학회 2010 대한전자공학회 학술대회 Vol.2010 No.6

This study considered optical principals and geometric elements of the lens, and analyzed the location of vanishing point through 3D model about the specific objet in the photo. In addition, it measured lens angle used to actual digital photographing by applying lens angle values from the focal distance based on 35mm film. Like this, if the completed measuring method is applied, lens angle of the digital photos can be found out without metadata. and using this theory we can find of object distance.

바닥 패턴을 이용한 단일영상 내의 피사체 크기 추출

황민구(Min-Gu Hwang),김동민(Dong-Min Kim),하동환(Dong-Hwan Har) 한국콘텐츠학회 2011 한국콘텐츠학회논문지 Vol.11 No.4

본 논문 단일영상 내에 존재하는 피사체의 정보를 객관적인 수치로 구현하는 데 목적이 있다. 이러한 연구를 위해서 2차원의 단일영상이 가진 소실점을 기초로 하였으며, 3D 프로그램을 이용하여 단일영상을 3차원으로 재구성하였다. 또한, 3차원 재구성에 필요한 촬영카메라의 축 설정을 위해서 이미지가 가진 렌즈 화각 및 바닥 패턴을 활용하였다. 이렇게 완성된 3차원 영상은 하나의 기준이 되는 특정 피사체의 크기 값을 안다면 바닥패턴에 있는 모든 피사체의 크기 및 거리 측정이 가능하며 이를 통해 CCTV 또는 기타 범죄 사건의 영상에서 범인 및 단서가 되는 피사체의 기초정보를 획득할 수 있다. This paper aims to realize the information of a subject existing in a still image with objective values. To attain the goal, this research takes the vanishing point that a 2D still image has as the basis and recomposes the still image into a 3D image using a 3D program. Also, in order to set up the axis of the camera necessary to recompose a 3D image, this paper used the lens angle of view that the image has and floor patterns as well. The 3D image completed in this way can measure the size and distance of all subjects in the floor patterns if the size value of a particular reference subject is known, and through this, it can be possible to acquire basic information of a subject that can be either a criminal or a clue in the images of CCTVs or some criminal scene.

광센서 조광제어시스템의 폴링주기 결정에 관한 연구

황민구(Min-Gu Hwang),최안섭(An-Seop Choi) 한국조명·전기설비학회 2005 한국조명·전기설비학회 학술대회논문집 Vol.2005 No.11월

Recently, energy depleting problem have risen seriously. Many studies of daylight responsive dimming system for saving of lighting energy in office buildings have been done actively. Most of studies are focused on the accuracy. However if the variation of dimming levels is changed too often, occupants would feel uncomfortable. First, illuminance changes which occupants couldn"t detect are studied through analyzing foreign studies. Second, workplan illuminance from daylight in each sky condition is measured. Because the dimming level in daylight responsive dimming system is dependent on the workplan illuminance from daylight. In conclusion, the most appropriate polling periods to daylight responsive dimming system for occupant"s visual comfort was determined.

광센서 조광제어시스템의 성능평가를 위한 소프트웨어 개발

황민구(Min-Gu Hwang),최안섭(An-Seop Choi) 한국조명·전기설비학회 2005 한국조명·전기설비학회 학술대회논문집 Vol.2005 No.5월

Recently, a drain of energy resources is issued seriously. The daylight responsive dimming systems can reduce electric energy uses. But, we cannot predict amounts of energy-saving and accuracy of system performance. Therefore, the purpose of this study is a development of software for the system performance of daylight responsive dimming systems. The principle of this software based on luminous flux transfer method and finite elements method. The control algorism of this software and daylight responsive dimming systems use the same algorithm. In addition the advantages of this software are use to same algorithm of daylight responsive dimming systems, electric power-luminous flux data and rates of frequency of sky conditions. Therefore, this software can predict more correct calculation about illuminance and amounts of energy-saving of daylight responsive dimming systems.

천공상태에 따른 광센서 조광제어시스템의 성능 및 정확성 향상에 관한 연구

황민구(Hwang. Min-Gu),최안섭(Choi. An-Seop) 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1

The daylight responsive dimming system have not be used widely for the deficiency of accuracy, confidence and technical data. The purpose of this research is to improve performance accuracy of the daylight responsive dimming systems by means of the study of control slope with sky condition variation. This paper analyzed the previous research and studied on whether the sky condition division can improve accuracy of this system or not. This paper also deeds with application method of the substantial sky condition division method using weather data into control s/w algorithm.

무전극 형광램프의 보급 및 확산을 위한 주력 제품군 선정

김진모(Jin-Mo Kim),정남용,신현정(Hyeon-Jeong Shin),박종환(Jong-Hwan Park),나영신(Young-Shin Na),황민구(Min-Gu Hwang) 한국조명·전기설비학회 2004 한국조명·전기설비학회 학술대회논문집 Vol.2004 No.5월

There are lots of merits in the electrodeless lighting. But it is not widely used because the price is too high though it has very good quality and efficiency. So it is necessary to develop a electrodeless lighting which can be widely used with its merit.