• Current Optics and Photonics
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• 제5권4호
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• pp.409-420
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• 2021

We propose a method to synthesize a color non-hogel-based computer-generated-hologram (CGH) from light field data of a three-dimensional scene with a hologram pixel pitch shared for all color channels. The non-hogel-based CGH technique generates a continuous wavefront with arbitrary carrier wave from given light field data by interpreting the ray angle in the light field to the spatial frequency of the plane wavefront. The relation between ray angle and spatial frequency is, however, dependent on the wavelength, which leads to different spatial frequency sampling grid in the light field data, resulting in color aberrations in the hologram reconstruction. The proposed method sets a hologram pixel pitch common to all color channels such that the smallest blue diffraction angle covers the field of view of the light field. Then a spatial frequency sampling grid common to all color channels is established by interpolating the light field with the spatial frequency range of the blue wavelength and the sampling interval of the red wavelength. The common hologram pixel pitch and light field spatial frequency sampling grid ensure the synthesis of a color hologram without any color aberrations in the hologram reconstructions, or any loss of information contained in the light field. The proposed method is successfully verified using color light field data of various test or natural 3D scenes.

• 전기학회논문지P
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• 제59권4호
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• pp.444-449
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• 2010

The PID control to the monitor color correction was applied. Converted Gamma LUT was applied to the video card. Color and brightness information from the PID controller was used as control inputs. Color and brightness information from a calibrated monitor is measured again. Then, the difference between the preset values for the PID controller was compensated by the feedback. The software measured by color meter was used for color and brightness information. All of the monitor does not measure the color and brightness was measured by sampling. The color and brightness from the monitor were measured not by complete enumeration but by sampling. In the experiment, the original image was displayed on the same monitor as well as two other brands, and then, Gamma and Contrast were measured and compared.

• 한국컴퓨터정보학회논문지
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• 제11권3호
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• pp.167-172
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• 2006

영상 검색 시스템이란 영상이 갖는 다양한 특징을 바탕으로 똑같거나 유사한 영상을 검색하여 제공하는 시스템이다. 본 논문에서는 영상의 컬러와 형태를 기반으로 한 상표 영상 검색 시스템을 제시한다. 영상을 영역별로 분할하고 영역별 컬러 분포 히스토그램을 추출하여 컬러 정보로 이용한다. 경계면 추출, 무게 중심 추출, angular 샘플링 등의 전처리 과정과 무게 중심으로부터 경계면 까지 거리의 합, 표준 편차, 장/단축 비율을 계산하여 형태정보로 이용한다. 이렇게 추출된 컬러와 형태 정보를 이용하여 유사성 측정을 통한 검색을 수행한다.

• 한국정보통신학회논문지
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• 제12권8호
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• pp.1356-1362
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• 2008

본 논문에서는 카메라가 가지는 대표적인 기능중의 하나인 자동 화이트 밸런스에 대한 알고리즘을 제안한다. 화이트 밸런스는 흰색의 물체나 물건 고유의 색이 아닌 부분들을 제거하는 과정이다. 화이트 밸런스를 수행하기 위해 사람의 눈에 의해 느끼는 시각차와 색차의 표현이 동일한 $CIEL^*a^*b^*$ 색 공간에서 영상의 분포를 분석하여 흰색 물체의 색 변화 정도를 추정한다. 이를 기준 백색 추정이라 한다. 정확한 추정을 위하여 환경에 의해 변화되었다고 추정되는 부분에 대해 그룹화 한다. 그룹화 된 영상 정보를 통해 영상의 특성을 파악하여 기준 그룹을 정하여 기준 그룹까지의 누적 픽셀들을 선택하는 컬러 샘플링하여 기준 백색을 추정한다. 또한 영상 보정을 위한 컬러 이득은 영상의 포화(Saturation)를 고려하여 얻어진다. 이를 통한 제안된 자동 화이트 밸런스 알고리즘은 뛰어난 영상 보정 기능을 가진다.

• 한국인쇄학회지
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• 제18권1호
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• pp.103-112
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• 2000

The color space transformation to link device-dependent color spaces and device-independent color spaces is essential for device characterization and cross-media color reproduction. There are various color conversion methods such as regression, 3D interpolation with LUT(look-up table), and neural network. In the color transformation with these methods, the conversion accuracy is essentially based on the sample data to be exploited for device characterization. In conventional method, color samples are uniformly selected in device-dependent space such as CMY and RGB. However, distribution of these color samples is very non-uniform in device-independent color space such as CIEL*a*b*. Accordingly, the conversion error in device-independent color space is irregular according to the distribution of the samples. In this paper, a color sampling method based on equi-visual perception is proposed to obtain approximate uniform color samples in CIEL*a*b* space. In order to evaluate transformation accuracy of proposed method, color space transformations are simulated using regression, 3D interpolation with LUT and neural network techniques, respectively.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 춘계학술대회
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• pp.160-161
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• 2010

본 논문에서는 컬러 정보와 형태 정보를 이용한 상표 영상 검색 시스템을 제안하였다. 컬러 정보는 영역을 분할하여 영역별 컬러 분포 히스토그램 특성에 근거한 컬러 정보를 이용하였고, 형태 정보는 경계면 추출, 무게 중심 추출, angular 샘플링 등의 전처리 과정과 무게 중심으로부터 경계면까지 거리의 합, 표준 편차, 장/단축 비율을 계산을 이용하였다. 특히, 무게중심을 이용한 angular 샘플링을 이용하여 특징을 추출하고 처리 시간을 줄일 수 있었다. 사용자는 컬러와 형태 정보에 의한 검색을 수행하고, 또한 가중치를 부여함으로써 두 방법을 혼합하여 사용할 수 있다.

• 대한의용생체공학회:의공학회지
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• 제16권3호
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• pp.279-288
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• 1995

Ultrasonic Doppler systems for the purpose of estimating blood flow velocity, blood flow volume, and flow imaging are commonly used due to advantages of non-invasive and real time observation. Specially, the technical developments of color flow mapping (2-D Doppler) systems have made a relatively rapid progress. However, the 2-D Doppler systems have several problems, such as the range ambiguity, low signal to noise ratio, and slow frame rate. The slow frame rate problem is resolved by using the spatial average which is a method to acquire more data samples for mean frequency estimation. In this paper, spatial average method using the 2nd order sampling instead of quadrature sampling is proposed. The experimental results show that the proposed methods have good performance and easy application to the color flow mapping system.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.816-819
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• 2006

One of the most difficult parameters to measure in the sea is current speed and direction. Recently, efforts are being made to estimate the ocean current vectors by utilizing sequential satellite imageries. In this study, we attempted to estimated sea surface current vector (sscv) by using satellite ocean color imageries of SeaWifs around the Korean Peninsula. This ocean color image data has 1-day sampling interval and spatial resolution of 1x1 km. Maximum cross-correlation method is employed which is aimed to detect similar patterns between sequential images. The estimated current vectors are compared to the surface geostrophic current vectors obtained from altimeter of sea level height data. In utilizing the color imagery data, some limitations and drawbacks exist so that in warm water region where phytoplankton concentration is relatively lower than in cold water region, estimation of sscv is poor and unreliable. On the other hand, two current vector fields agree reasonably well in the Korean South Sea region where high concentration of chlorophyll-a and weak tide is observed. In the future, with ocean color images of shorter sampling interval by COMS satellite, the algorithm and methodology developed in the study would be useful in providing the information for the ocean current around Korean Peninsula.

• IEIE Transactions on Smart Processing and Computing
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• 제3권1호
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• pp.10-18
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• 2014

From the perspective of reducing the sampling cost of color images at high resolution, block-based compressive sensing (CS) has attracted considerable attention as a promising alternative to conventional Nyquist/Shannon sampling. On the other hand, for storing/transmitting applications, CS requires a very efficient way of representing the measurement data in terms of data volume. This paper addresses this problem by developing a measurement-coding method with the proposed customized Huffman coding. In addition, by noting the difference in visual importance between the luma and chroma channels, this paper proposes measurement coding in YCbCr space rather than in conventional RGB color space for better rate allocation. Furthermore, as the proper use of the image property in pursuing smoothness improves the CS recovery, this paper proposes the integration of a low pass filter to the CS recovery of color images, which is the block-based ${\ell}_{20}$-norm minimization. The proposed coding scheme shows considerable gain compared to conventional measurement coding.

• 방송공학회논문지
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• 제18권4호
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• pp.647-650
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• 2013

HEVC RExt(High Efficiency Video Coding Range Extension)는 RGB/YUV 4:2:2 4:4:4 색 샘플링 영상과 10비트 심도 이상의 영상 지원을 목표로 한다. RGB 영상은 YUV 4:2:0 색 샘플링 영상과는 달리 색평면 간 높은 상관도를 갖고 있으며, 이를 이용하여 화소값을 예측하는 기법들이 JCT-VC 표준화 회의에서 기고되었다. 하지만 일반적으로 RGB 영상의 고주파수 성분은 색평면 간 낮은 상관도를 갖고 있으며, 이는 색평면 간 예측 시 부호화 효율 저하의 원인이 된다. 따라서 본 논문에서는 색평면 간 예측 시 고주파수 성분을 저역통과필터를 통해 적응적으로 제거하는 기법을 제안한다. HEVC RExt의 RGB 영상을 통한 실험 결과, 본 논문에서 제안하는 기법은 기존 색평면 간 예측 기법에 비해 큰 복잡도의 증가 없이 평균 0.6%의 BD(Bjontegaard Distortion)-율 이득을 얻을 수 있었다.