Kyu-Ik Sohng

Kyungpook National University, Daikyū, Daegu, South Korea

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Publications (95)23.07 Total impact

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    ABSTRACT: An image appearance model is extremely useful for high-dynamic-range image (HDRI) rendering. However, the base-detail separation and the tone compression process for tonal control cause degradations in image quality. This study focuses on the de-saturation, reduced contrast, and noise problems in dark regions that occur through HDRI-rendering. First, we discuss de-saturation compensation using a bilateral filter that is based on the visual acuity characteristics of various illuminant levels. The edge stop function of the bilateral filter in iCAM06 is adaptively modified according to the illuminant information. Second, to reduce the magnified noise in the dark regions caused by tone mapping, the shadow regions are detected by an object’s intensity and illuminant level, and then the noise of the detected regions is reduced using a luminance-adaptive coring function. Finally, we confirmed the enhanced color saturation, image contrast, and reduced noise in shadow regions through the application of the proposed methods.
    Optical Review 04/2015; 22(2):232-245. DOI:10.1007/s10043-015-0065-x · 0.55 Impact Factor
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    Sung-Hak Lee, Hyuk-Ju Kwon, Kyu-Ik Sohng
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    ABSTRACT: A low-dynamic tone-compression technique is developed for realistic image rendering that can make three-dimensional (3D) images similar to realistic scenes by overcoming brightness dimming in the 3D display mode. The 3D surround provides varying conditions for image quality, illuminant adaptation, contrast, gamma, color, sharpness, and so on. In general, gain/offset adjustment, gamma compensation, and histogram equalization have performed well in contrast compression; however, as a result of signal saturation and clipping effects, image details are removed and information is lost on bright and dark areas. Thus, an enhanced image mapping technique is proposed based on space-varying image compression. The performance of contrast compression is enhanced with complex adaptation in a 3D viewing surround combining global and local adaptation. Evaluating local image rendering in view of tone and color expression, noise reduction, and edge compensation confirms that the proposed 3D image-mapping model can compensate for the loss of image quality in the 3D mode.
    Optical Review 07/2014; 21(4):440-447. DOI:10.1007/s10043-014-0068-z · 0.55 Impact Factor
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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 07/2014; 30. DOI:10.1016/j.dsp.2014.03.008 · 1.50 Impact Factor
  • 12/2013; 6(6):151-162. DOI:10.14257/ijca.2013.6.6.15
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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.
    08/2013; 38A(8). DOI:10.7840/kics.2013.38A.8.669
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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. DOI:10.1016/j.jvcir.2012.03.001 · 1.36 Impact Factor
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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.
    03/2013; 16(3). DOI:10.9717/kmms.2013.16.3.281
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    Seok-Min Chae, Sung-Hak Lee, Kyu-Ik Sohng
    IEICE Transactions on Electronics 01/2013; E96.C(11):1408-1412. DOI:10.1587/transele.E96.C.1408 · 0.39 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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    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.
    12/2012; 37A(12). DOI:10.7840/kics.2012.37A.12.1054
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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 07/2012; E95.D(7):1823-1826. DOI:10.1587/transinf.E95.D.1823 · 0.19 Impact Factor
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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. DOI:10.1587/transfun.E95.A.1297 · 0.23 Impact Factor
  • Sung-Hak Lee, Kyu-Ik Sohng
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    ABSTRACT: The color appearance model gives us the proper brightness information and optimized display conditions for various viewing surroundings. However on conditions of low-level illumination or low background reflectivity, the performance of brightness estimation is relatively poor. Therefore, through our psychophysical experiments, we investigated the state of visual luminance adaptation for comparing single adaptations and mixed adaptations under a complex viewing field, and we also investigated background adaptation degrees and exponential nonlinearity factors for mixed adaptation models. It provides more accurate brightness predictions according to different adapting luminance, which is decided from object and background luminance.
    IEICE Transactions on Electronics 11/2011; 94-C(11):1768-1772. DOI:10.1587/transele.E94.C.1768 · 0.39 Impact Factor
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    ABSTRACT: An image appearance model called iCAM06 was designed for high dynamic range (HDR) image rendering. The dynamic range of an HDR image needs to be mapped on output devices, which is called tone compression or tone mapping. The iCAM06, the representative HDR rendering algorithm, uses tone compression for image reproduction on the low dynamic range of output devices. However, color saturation reduction occurs during its tone compression process. We propose a saturation correction method using the inverse compensation in order to recover the saturation reduction in the iCAM06. Experimental results show that the proposed method has better performance than the iCAM06 from the view-point of saturation accuracy and rendering preference.
    IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences 11/2011; 94-A(11):2353-2357. DOI:10.1587/transfun.E94.A.2353 · 0.23 Impact Factor
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    ABSTRACT: Mathematical morphology techniques, such as white top-hat (WTH) and new white top-hat (NWTH) transformation have been researched for small target detection application in the infrared (IR) images. However, its target enhancement performance still depends on its SE size set by users. To solve this problem, we propose a recursive multi-structuring elements (multi-SEs) NWTH method with an automatic decision mechanism of the SE size. The proposed method based on the NWTH transformation updates the multi-SEs by calculating candidate target-to-clutter ratio gain (CTCRG) of the NWTH images by the multi-SEs. Through a recursive procedure, final multi-SEs is automatically selected, and then small targets can be detected in a summation image of NWTH images by the final multi-SEs.
    IEICE Electronics Express 10/2011; 8(19):1576-1582. DOI:10.1587/elex.8.1576 · 0.39 Impact Factor
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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.
    09/2011; 36(9C). DOI:10.7840/KICS.2011.36C.9.546
  • Sung-Hak Lee, Tae-Wuk Bae, Kyu-Ik Sohng
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    ABSTRACT: We proposed a method for reducing LCD motion blur in MPEG domain and analyzing the cause of LCD motion blur. The problem of LCD motion blur is caused by slow response time of liquid crystal and hold-type displaying method of LCDs. The proposed method uses MPEG motion vectors and frequency coefficients of DCT blocks to improve the motion blurs. First, we interpreted the aperture and response time effect of LCD in frequency domain then, modeled sharpening mask filters for the compensation. We confirmed the reduction of motion blurs in LCDs by a motion image simulator.
    IEICE Transactions on Electronics 11/2010; 93-C:1612-1615. DOI:10.1587/transele.E93.C.1612 · 0.39 Impact Factor
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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 11/2010; 36(6):1156-1164. DOI:10.1016/j.compeleceng.2010.05.004 · 0.99 Impact Factor
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    ABSTRACT: This paper proposes a new auto flesh tone balance algorithm for the picture that is taken for people. In this paper, the basis of auto white balance (AWB) is human face in photo. For experiment, the transfer characteristic of camera image sensor is analyzed and the camera output RGB is calculated by measuring the average face chromaticity under standard illuminant. For the face region taken under unknown illuminant, the proposed algorithm makes RGB output rate of face region become its rate of standard face color. For this, it adjusts the R and B channel and performs the chromaticity correction. Algorithm is applied to the light skin color (average face color) in Macbeth color chart and average color of various face colors that are actually measured.
    IEICE Transactions on Electronics 11/2010; 93-C:1616-1620. DOI:10.1587/transele.E93.C.1616 · 0.39 Impact Factor
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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