• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.592-594
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• 2002

일반적으로 디지털 영상에 대한 기존 워터마킹 기법은 기하학적인 왜곡에 허약하다. 본 논문에서는 기하학적인 왜곡에 강건한 워터마킹 기법을 제안한다. 워터마킹 기법은 워터마크의 생성단계 워터마크 삽입단계, 워터마크 추출 단계로 구성된다. 워터마크 생성단계에서는 시각적으로 구별이 가능한 그레이 영상을 워터마크로 사용하며, 워터마크 삽입 단계에서는 원 영상을 콤플렉스 웨이블릿 변환하여 위상 정보에 워터마크를 삽입한다. 그리고 워터마크 추출 단계에서는 워터마크된 영상으로부터 계층적으로 워터마크를 추출하여 자기 상관관계 비교에 의해 워터마크를 추출한다. 실험 결과를 통하여 이동, 크기 변환, 회전과 같은 기하학적인 변형에도 워터마크가 추출되는 것을 볼 수 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.560-570
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• 2017

Recently, well-known SAR imaging algorithms have been developed to form the focused SAR images for stationary targets. In general, the conventional methods exploit the range variation only defined by the motion of radar platform and SAR geometry. However, for SAR imaging of ground moving targets, the motion of the targets induces an additional range shift, yielding the blurred SAR images. To overcome the problem, in this paper we propose an effective motion compensation algorithm operated under a multi-channel SAR, named along-track interferometry(ATI) and phase unwrapping to directly estimate the motion parameters of the targets. In simulations, 50 Monte-Carlo simulation results show the effectiveness of the algorithm in the presence of noise.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.1-8
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• 2011

Automatic vehicle license plate recognition technology is widely used in gate control and parking control of vehicles, and police enforcement of illegal vehicles. However inherent geometric information of the license plate can be transformed in the vehicle images due to the slant and the sunlight or lighting environment. In this paper, a distortion invariant vehicle license plate extraction and recognition algorithm is proposed. First, a binary image reserving clean character strokes can be achieved by using a DoG filter. A plate area can be extracted by using the location of consecutive digit numbers that reserves distortion invariant characteristic. License plate is recognized by using neural networks after geometric distortion correction and image enhancement. The simulation results of the proposed algorithm show that the accuracy is 98.4% and the average speed is 0.05 seconds in the recognition of 6,200 vehicle images that are obtained by using commercial LPR system.

• Korean Journal of Remote Sensing
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• v.19 no.6
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• pp.431-445
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• 2003

In this paper, we experimentally investigated the precision of 3D positioning using 4S-Van images in photograrmmetric perspective. The 3D calibration target was built over building facade outside and was captured separately by two CCD cameras installed in 4S-Van. After then, we determined the interior orientation parameter for each CCD camera through self-calibration technique. With the interior orientation parameter computed, the bundle adjustment was performed to obtain the exterior orientation parameters simultaneously for two CCD cameras using calibration target image and object coordinates. The reverse lens distortion coefficients were computed and acquired by least squares method so as to introduce lens distortion into epipolar line. It was shown that the reverse lens distortion coefficients could transform image coordinates into lens distorted image coordinates within about 0.5 pixel. The proposed semi-automatic matching scheme incorporated with lens distorted epipolar line was implemented with scene images captured by 4S-Van in moving. The experimental results showed that the precision of 3D positioning from 4S-Van images in photograrmmetric perspective is within 2cm in the range of 20m from the camera.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.150-153
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• 2014

영상 표시 장치에서 대조 이미지의 왜곡 현상을 보완하기 위해 히스토그램 평활화(Histogram Equalization)와 플래토 평활화(Plateau Equalization)가 사용된다. 히스토그램 평활화(Histogram Equalization)를 이용하여 명암대비를 증가 시킬 경우 과도한 이미지의 밝기 변화에 따른 과포화 현상이 발생하며 실시간 시스템에서는 물체 추적에 왜곡 현상이 발생한다. 특히, 적외선 영상(infrared image)과 같이 명암비가 한쪽으로 치우쳐 있는 영상들을 명암비를 개선하기 위해서는 플래토 평활화(Plateau Equalization)와 같은 영상 개선 방법이 필수적이다. 플래토 평활화에서는 임계값을 사용하는 방법이 제시되고 있지만 실험에 의한 최적 임계값을 찾아내는 방식이며, 이 방법은 입력되는 새로운 영상마다 임계값을 실험에 의해 매번 반복해서 도출해야 문제점이 있다. 본 논문에서 제안하는 방법은 과포화 되는 이미지 영역의 문제를 해결하기 위해 제시하는 방법으로 히스토그램 평활화(Histogram Equalization)의 동적 분할하는 알고리즘에 근거하되, 입력 영상에따라 적응적으로 임계값을 설정하는 기법을 제안한다. 실험을 통해 제안하는 방법이 실시간 영상에서 기존의 동적분할 히스토그램에 비해 자연스럽게 명암비를 개선하여 과포화 되거나 중요한 정보를 누락하여 왜곡 되지 않게 자연스러운 화면을 재생하는 방법을 제안한다.

• Journal of the Korea Computer Graphics Society
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• v.25 no.5
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• pp.1-9
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• 2019

In this paper, we propose a video enhancement method using generative adversarial networks to remove raindrops and restore the background information on the removed region in the coastal wave video imagery distorted by raindrops during rainfall. Two experimental models are implemented: Pix2Pix network widely used for image-to-image translation and Attentive GAN, which is currently performing well for raindrop removal on a single images. The models are trained with a public dataset of paired natural images with and without raindrops and the trained models are evaluated their performance of raindrop removal and background information recovery of rainwater distortion of coastal wave video imagery. In order to improve the performance, we have acquired paired video dataset with and without raindrops at the real coast and conducted transfer learning to the pre-trained models with those new dataset. The performance of fine-tuned models is improved by comparing the results from pre-trained models. The performance is evaluated using the peak signal-to-noise ratio and structural similarity index and the fine-tuned Pix2Pix network by transfer learning shows the best performance to reconstruct distorted coastal wave video imagery by raindrops.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.789-792
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• 2011

자동차를 위한 전방향(omnidirectional) 감시 시스템, 교통 정보 수집 시스템 등 다양한 비젼 시스템에 카메라가 장착되어 사용되고 있다. 최근에는 운전자의 편의를 위하여 광각 카메라의 비선형적인 방사 왜곡을 해결하는 왜곡 보정 작업 등의 영상처리 시스템이 많이 발전하여 운전자의 사각지대를 효율적으로 최소화하고 있다. 그러나 기존의 연구에서는 카메라로부터 입력되는 왜곡 영상을 보정하는데에 별도의 H/W인 DSP(Digital Signal Processes) 또는 SOC(System On Chp) 형태의 전용 H/W를 추가하여 임베디드 시스템의 성능을 보완하고 있다. 하지만 위와 같은 별도의 H/W를 추가하여 임베디드 시스템의 성능을 보완할 경우 시스템이 복잡해지고 가격이 비싸진다는 단점이 있다. 본 논문에서는 이러한 문제점을 보완하기 위하여 왜곡 보정 알고리즘과 호모그래피(Homography) 알고리즘의 연산량을 감소시켜 임베디드 시스템 환경에서 추가의 H/W 비용없이 왜곡 보정을 수행하는 알고리즘을 제안하고, 제안한 알고리즘을 구현하여 실제 시스템에 적용한 결과를 제시하여 구현 타당성을 검증한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.11a
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• pp.90-92
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• 2018

본 논문에서는 입력 영상을 카메라의 자세 정보에 따라 적절히 와핑한 후 이들을 심(Seam)을 따라 이어붙인 360VR 에서 갑작스런 객체 출현에 의해 중첩 영역에서 발생하는 왜곡 문제를 해결할 방법을 제안한다. 임의의 객체가 나타났을 때, 객체의 윤곽선을 반영하여 심(Seam)을 재설정함으로써 객체가 우그러지거나, 잘려나가는 등의 왜곡 문제를 해결한다. 이를 위해 본 논문에서는 가우시안(Gaussian) 혼합 모델 기반 전경/배경분리에 의한 움직이는 객체 추출, 객체 윤곽선 검출, 윤곽선에 기반한 심(Seam) 조정, 새로운 심(Seam) 기반 스티칭으로 왜곡을 없애는 방법을 제안하였다. 그리고 이를 실제 촬영 영상에 적용하여 왜곡 개선 효과를 보였다.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.5
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• pp.555-563
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• 2011

The goal of image calibration is to find a relation between image and world coordinates. Conventional image calibration uses physical camera model that is able to reflect camera's optical properties between image and world coordinates. In this paper, we try to calibrate images distortion using performance criterion-based polynomial model which assumes that the relation between image and world coordinates can be identified by polynomial equation and its order and parameters are able to be estimated with image and object coordinate values and performance criterion. In order to overcome existing limitations of the conventional image calibration model, namely, over-fitting feature, the performance criterion-based polynomial model is proposed. The efficiency of proposed method can be verified with 2D images that were taken by laser scan camera.

• Journal of the Korean Society of Radiology
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• v.15 no.3
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• pp.321-327
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• 2021

Wrist PA-grip view is used to diagnose triangular fibrocartilage complex (TFCC) tear because it can easily diagnose damage to the surrounding wrist ligaments. However, despite advances in radiology equipment, distortion of images due to geometric elements still has many limitations. In this paper, we propose a method that can minimize the distortions of images by analyzing the distortions occurring in the wrist PA-grip view. A source of image distance (SID) were set at 130 cm and 150 cm for comparison with 110 cm. Depending on the SID, the phantom of wrist was moved at 0, 2, 4, 6, 8, and 10 cm in the X-axis and Y-axis directions, respectively. For quantitative evaluation, the difference of distance between the radius and ulna was measured in picture archiving and communication system (PACS) system. As a qualitative evaluation, survey was conducted among 20 radiologic technologists who examined the Wrist PA-grip view. The Kruskal Wallis test was performed to compare the distortion according to the phantom movement in the X-axis and Y-axis directions based on the SID, and the Tukey test was performed as a post-test. In the quantitative evaluation results, the measured values obtained in the X-axis was not significantly different in all groups (p>0.05). The measured values obtained in the Y-axis was significantly different in the most groups (p<0.05). Therefore, to reduce distortion while maintaining image quality, we recommend what examine the SID at 150 cm than 110 cm.