Kyu-Ik Sohng

Kyungpook National University, Daikyū, Daegu, South Korea

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Publications (86)12.05 Total impact

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    ABSTRACT: Tone mapping algorithms are used for image processing to reduce the dynamic range of an image to be displayed on low dynamic range (LDR) devices. The Retinex, which was developed using multi-scale and luminance-based methods, is one of the tone mapping algorithms for dynamic range compression, color constancy and color rendition. Retinex algorithms still have drawbacks, such as lower contrast and desaturation. This paper proposes a multi-scale luminance adaptation transform (MLAT) based on visual brightness functions for the enhancement of contrast and saturation of rendered images. In addition, the proposed algorithm was used to estimate the minimum and maximum luminance and a visual gamma function for local adapted viewing conditions. MLAT showed enhanced contrast and better color representation than the conventional methods in the objective evaluations (CIEDE200 and VCM).
    Digital Signal Processing 01/2014; · 1.92 Impact Factor
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    ABSTRACT: The iCAM06, a high dynamic range rendering process, contains chromatic adaptation method based on the CIECAM02 model. The D factor, degree of adaptation, in the chromatic adaptation of the iCAM06 is the function of the adapting luminance level, but it does not consider the visual white point shift according to the variation of luminance level. The iCAM06 acquires a blurred illuminant image. So, each pixel has a different illuminant color. When some of the colors cover the entire image, a de-saturation effect appears around these colors. The simply modified D factor to reduce the de-saturation effect causes unsuitable changes in the degree of adaptation. Therefore, we propose a new method to find the global illuminant information and the D factor for the illuminant in the HDR image rendering process. Comparing the proposed with the conventional method, we confirm that the proposed method provides better illuminant estimation and color representation.
    Journal of Visual Communication and Image Representation 08/2013; 24(6):678–685. · 1.20 Impact Factor
  • Geun-Young Lee, Sung-Hak Lee, Kyu-Ik Sohng
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    ABSTRACT: In pursuance of the tone mapping for LDR images, the proposed method inserts the tone mapping into JPEG baseline not as post-processing. First, an image is decomposed in detail, base, surround images in term of DCT coefficients. Then, a surround-adaptive tone mapping is applied to the base image. In addition, a compensation module is added for the defects such as desaturation and sharpness falling resulted by tone mapping. As a result, it is confirmed that transmitted JPEG images are enhanced in term of image quality.
    Consumer Electronics (GCCE), 2013 IEEE 2nd Global Conference on; 01/2013
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    Seok-Min Chae, Sung-Hak Lee, Kyu-Ik Sohng
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    ABSTRACT: The iCAM06 has been used as an image appearance model for HDR image rendering. The iCAM06 goes through the color space conversions and scale conversions of the several steps to present HDR images. The dynamic range of an HDR image needs to be mapped on the range of output devices, which is called the tone mapping. However, tone compression process of the iCAM06 causes color distortion because of color-clipping and cross-stimulus. Therefore, we proposed that a color correction method in IPT space which compensates the color distortion in tone compression process. Through the experimental results, we conformed that proposed color correction method had better performance than the iCAM06 and enhanced models.
    Journal of Korea Multimedia Society. 01/2013; 16(3).
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    ABSTRACT: When an image is converted from HDR (high dynamic range) to LDR (low dynamic range), a tone mapping process is the essential component. Many TMOs (tone mapping operators) have been motivated by human vision which has lower physical luminance range than that in real scene. The representative of human vision properties which motivate TMOs is the local adaptation. However, TMOs are ultimately compressing image information such as contrast, saturation, etc. and the compression causes defects in image quality. In this paper, in order to compensate the degradation of the image which is caused by TMOs, the visual acuity-based edge stop function is proposed for applying the property of human vision to base-detail separation. In addition, using CSF (contrast sensitivity function) which represents the relationship among spatial frequency, contrast sensitivity, and luminance, the sharpness filter is designed and adaptively applied to the detail layer in regard to surround luminance.
    The Journal of Korea Information and Communications Society. 01/2013; 38A(8).
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    ABSTRACT: HDR (high dynamic range) tone mapping algorithms are used in image processing that reduces the dynamic range of an image to be displayed on LDR (low dynamic range) devices properly. The retinex is one of the tone mapping algorithms to provide dynamic range compression, color constancy, and color rendition. It has been developed through multi-scale methods and luminance-based methods. Retinex algorithms still have drawbacks such as the emphasized noise and desaturation. In this paper, we propose a multi scale tone mapping algorithm for enhancement of contrast, saturation, and noise of HDR rendered images based on visual brightness functions. In the proposed algorithm, HSV color space has been used for preserving the hue and saturation of images. And the algorithm includes the estimation of minimum and maximum luminance level and a visual gamma function for the variation of viewing conditions. And subjective and objective evaluations show that proposed algorithm is better than existing algorithms. The proposed algorithm is expected to image quality enhancement in some fields that require a improvement of the dynamic range due to the changes in the viewing condition.
    The Journal of Korea Information and Communications Society. 01/2012; 37A(12).
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    ABSTRACT: Recently, a new image appearance model, named iCAM06, was developed for High-Dynamic-Range (HDR) image rendering. The dynamic range of a HDR image needs to be mapped onto the range of the output device where it will be displayed, this is called tone reproduction or tone mapping. iCAM06, a representative HDR rendering algorithm also uses tone compression for image reproduction on the dynamic range of output devices. However, iCAM06 causes a white point shift during its tone compression process. Therefore, we propose a compensation method for white point shifts using corrected channel gain. Experiment results show that the proposed method has better performance than iCAM06.
    IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences 01/2012; E95.A(8):1297-1301. · 0.24 Impact Factor
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    ABSTRACT: In this study, we show that the motion blur is caused by exposure time of video camera as well as the characteristics of LCD system. Also, we suggest that evaluation method of motion picture quality according to the frequency response of video camera and LCD systems of hold and scanning backlight type.
    IEICE Transactions on Information and Systems 01/2012; E95.D(7):1823-1826. · 0.22 Impact Factor
  • Sung-Hak Lee, Kyu-Ik Sohng
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    ABSTRACT: A Model of Luminance-Adaptation for Quantifying Brightness in Mixed Visual Adapting Conditions
    IEICE Transactions. 01/2011; 94-C:1768-1772.
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    ABSTRACT: Near targets in the infrared (IR) images have the steady feature for inner region and the transient feature for the boundary region. Based on these features, this paper proposes a new method to extract the fine target shape of near targets in the IR images. First, we detect the boundary region of the candidate targets using the local variance weighted information entropy (WIE) of the original images. And then, a coarse target region can be estimated based on the labeling of the boundary region. For the coarse target region, we use the opening filter with an adaptive structure element to extract the fine target shape. The decision of the adaptive structure element size is optimized for the width information of target boundary by calculating the average WIE in the enlarged windows. The experimental results show that a proposed method has better extraction performance than the previous threshold algorithms.
    The Journal of Korea Information and Communications Society. 01/2011; 36(9C).
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    ABSTRACT: Color Saturation Compensation in iCAM06 for High-Chroma HDR Imaging
    IEICE Transactions. 01/2011; 94-A:2353-2357.
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    ABSTRACT: In this paper, we implement a reticle seeker missile simulator on MATLAB-SIMULINK to analyze the jamming effect of the spin-scan and conscan reticle seeker. The DIRCM (Directed Infrared Countermeasures) system uses the pulsing flashes of infrared (IR) energy and its frequency and intensity have influence on the missile guidance system. Our simulation results show that jamming effect is indicated significantly when jammer frequency and reticle frequency are similar and present a 3D trajectory of missile motions by jamming.
    Image Processing Theory Tools and Applications (IPTA), 2010 2nd International Conference on; 08/2010
  • Sung-Hak Lee, Kyu-Ik Sohng
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    ABSTRACT: The visual attributes, brightness, colorfulness, and hue, are affected by chromaticity coordinates, excitation purity, and luminance of background, and these attributes are changed according as intensity of illumination changes. Therefore there is a need to correct display's conditions by controlling image factors such as luminance offset, contrast, color gain, and gamma to maintain the perceived display quality. The focus of our study is on the formulation of a simpler and more effective model for color and tone reproduction for digital imaging systems to utilize color appearance models. It can be applicable to optimum color display conditions to give comfort and consistency visually in various ambient conditions.
    IEICE Transactions. 01/2010; 93-A:1453-1456.
  • Proceedings of the 2010 International Conference on Image Processing, Computer Vision, & Pattern Recognition, IPCV 2010, July 12-15, 2010, Las Vegas, Nevada, USA, 2 Volumes; 01/2010
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    ABSTRACT: In this paper, we present an auto-range fast bilateral filter (FBF) for high-dynamic-range (HDR) images, which increases computation speed by using adaptive standard deviations for range filter (RF) of FBF in iCAM06. Many images that cover the entire dynamic range of the scene with different exposure times are fused into one High Dynamic Range (HDR) image. The representative algorithm for HDR image rendering is iCAM06, which is based on the iCAM framework, such as the local white point adaptation, chromatic adaptation, and the image processing transform (IPT) uniform color space. FBF in iCAM06 uses constant standard deviation in RF. So, it causes unnecessary FBF computation in high stimulus range with broad and low distribution. To solve this problem, the low stimulus image and high stimulus image of CIE tri-stimulus values (XYZ) divided by the threshold are respectively processed by adaptive standard deviation based on its histogram distribution. Experiment results show that the proposed method reduces computation time than the previous FBF.
    The Journal of Korea Information and Communications Society. 01/2010; 35(4C).
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    ABSTRACT: We proposed an occupant sensing system using single video camera and ultrasonic sensor for the advanced airbag. To detect the occupant form and the face position in real-time, we used the skin color and motion information. We made the candidate face block image using the threshold value of the color difference signal corresponding to skin color and difference value of current image and previous image of luminance signal to gel motion information. And then it detects the face by the morphology and the labeling. In case of night without color and luminance information, it detects the face by using the threshold value of the luminance signal get by infra-red LED instead of the color difference signal. To evaluate the performance of the proposed occupant detection system, it performed various experiments through the setting of the IEEE camera, ultrasonic sensor, and infra-red LED in vehicle jig.
    Journal of Korea Multimedia Society. 01/2010; 13(1).
  • Proceedings of the 2010 International Conference on Image Processing, Computer Vision, & Pattern Recognition, IPCV 2010, July 12-15, 2010, Las Vegas, Nevada, USA, 2 Volumes; 01/2010
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    Sung-Hak Lee, Jong-Hyub Lee, Kyu-Ik Sohng
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    ABSTRACT: Color image sensors (CIS) output color images through image sensors and image signal processing. Image sensors that convert light to electrical signal are divided into CMOS image sensor and CCD image sensor according to transferring method of signal charge. In general, a CIS has RGB output signals from tri-stimulus XYZ of the scene through image signal processing. This paper presents an adaptive colorimetric analysis method to obtain chromaticity and luminance using CIS under various environments. An image sensor for the use of colorimeter is characterized based on the CIE standard colorimetric observer. We use the method of least squares to derive a colorimetric characterization matrix between camera RGB output signals and CIE XYZ tristimulus values. We first survey the camera characterization in the standard environment then derive a SGL(shutter-gain-level) function which is relationship between luminance and auto exposure (AE) characteristic of CIS, and read the status of an AWB(auto white balance) function. Then we can apply CIS to measure luminance and chromaticity from camera outputs and AE resister values without any preprocessing. Camera RGB outputs, register values, and camera photoelectric characteristic are used to analyze the colorimetric results for real scenes such as chromaticity and luminance. Experimental results show that the proposed method is valid in the measuring performance. The proposed method can apply to various fields like surveillant systems of the display or security systems.
    Journal of Korea Multimedia Society. 01/2010; 13(5).
  • Sung-Hak Lee, Tae-Wuk Bae, Kyu-Ik Sohng
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    ABSTRACT: Enhancement of LCD Motion Picture Quality Using the Motion Compensated Sharpening Mask Filter in MPEG Domain
    IEICE Transactions. 01/2010; 93-C:1612-1615.
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    ABSTRACT: This paper presents a new small target detection method using cross product of temporal pixels based on temporal profiles in infrared (IR) image sequences. Temporal characteristics of small targets and various backgrounds are different. A new algorithm classifies target pixels and background pixels through hypothesis testing using the cross product of pixels on temporal profile and predicts the temporal backgrounds based on the results. Small target pixels are detected by subtracting the predicted temporal background profile from the original temporal profile. For performance comparison between the proposed method and the conventional methods, the receiver operating characteristics (ROC) curves were computed experimentally. Experimental results show that the proposed algorithm has better discrimination of target and clutter pixels and lower false alarm rates than conventional methods.
    Computers & Electrical Engineering. 01/2010; 36:1156-1164.