• Journal of the Institute of Convergence Signal Processing
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• v.5 no.4
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• pp.287-293
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• 2004

This paper proposes an efficient motion compensation algorithm for video sequences with brightness variations. In the proposed algorithm, the brightness variation parameters are estimated and local motions are compensated. To detect the frame with large brightness variations, we employ the frame classification based on the cross entropy between histograms of two successive frames, which can reduce the computational redundancy. Simulation results show that the proposed method yields a higher peak signal to noise ratio (PSNR) than that of the conventional methods, with a low computational load, when the video scene contains large brightness changes.

• Journal of Broadcast Engineering
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• v.24 no.1
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• pp.3-24
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• 2019

Techniques related to 360 VR service have been developed to improve the quality of the stitched image and video, where illumination compensation scheme is one of the important tools. Among the conventional illumination compensation algorithms, Gain-based compensation and Block Gain-based compensation algorithms have shown the outstanding performances in the process of making panorama picture. However, those are ineffective in the 360 VR service, because the disparity between illuminations of the multiple pictures in 360 VR is much more than that in making the panorama picture. In addition, the number of the pictures to be stitched in 360 VR system is more than that in the conventional panorama image system. Thus, we propose a preprocessing tool to enhance the illumination compensation algorithm so that the method reduces the degradation in the stitched picture of 360 VR systems. The proposed algorithm consists of 'color compensation' and 'illumination compensation'. The simulation results show that the proposed technique improve the conventional techniques without additional complexity.

• Journal of Broadcast Engineering
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• v.7 no.4
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• pp.291-299
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• 2002

This paper proposes an efficient motion compensation algorithm for video sequences with brightness variations. In the proposed algorithm, the brightness variation parameters are estimated and local motions are compensated. To detect the frame with large brightness variations. we employ the frame classification based on the cross entropy between histograms of two successive frames, which can reduce the computational redundancy. Simulation results show that the proposed method yields a higher peak signal to noise ratio (PSNR) than the conventional methods, with a low computational load, when the video scene contains large brightness changes.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.3
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• pp.347-352
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• 2011

Entropy used for measuring the richness in details of the image and absolute mean brightness error(AMBE) providing a change in the image global appearance are two quantitative measures generally used for measuring quality of images. In this paper, we propose an entropy and AMBE-based thresholding method to binalize a given image. The effectiveness of the proposed method is demonstrated by thresholding experiments on nine test images and comparison with other conventional thresholding methods, that is, Otsu method and entropy-based method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5C
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• pp.512-518
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• 2006

Very large-area multi-projector display systems have wide applications since they provide immersible environments. The brightness of projectors in the system is different due to the design and aging of the bulbs, and optical properties of the projectors. Therefore it is imperative to match the brightness characteristics of projectors in the system. This issue has been addressed by many researchers. The state of the art solution considers characteristic of projector's brightness only. In this paper, we propose a method that takes into account brightness of projector as well as the dynamic range of the input image. We increase the dynamic range of the input image to utilize the maximum possible brightness of a projector while satisfying the spatial smoothness constraint. This achieves a seamless multi-display with dramatic brightness improvement.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.464-475
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• 2019

We measured night sky brightness (NSB) over the downtown using a Digital Single Lens Reflex (DSLR) camera combined to a small telescope for educational purpose, considering that most secondary schools are located in urban areas and have limitation in the equipment for astronomical observation. Raw format images from DSLR camera are not affected by various camera settings except for the ISO, and the typical photometric uncertainty including filter transformation is about 0.1 mag. Near the zenith, the NSB of the B, V, and r-band is 17.5, 17.1, and $16.9mag\;arcsec^{-2}$, respectively. The approximate limiting magnitude is derived to be 17.5 mag at B-band and 17 mag at V, r-band. A large scale artificial light close to the observation site is the dominant cause for making observing condition worse, increasing the NSB by $0.6mag\;arcseec^{-2}$ regardless of the altitude and filter.

• Journal of Broadcast Engineering
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• v.22 no.6
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• pp.808-816
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• 2017

360 VR video systems has become important to provide immersive effect for viewers. The system consists of stitching, projection, compression, inverse projection, viewport extraction. In this paper, an efficient luminance compensation technique for 360 VR video sequences, where feature extraction and histogram equalization algorithms are utilized. The proposed luminance compensation algorithm enhance the performance of stitching in 360 VR system. The simulation results showed that the proposed technique is useful to increase the quality of the displayed image.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.77-86
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• 2014

Mobile devices are generally using app images which are artificially designed. Accordingly, this paper presents adjusting device brightness based on app image categorization for enhancing the visibility under various light condition. First, the proposed method performed two prior subjective tests under various lighting conditions for selecting features of app images concerning visibility and for selecting satisfactory range of device brightness for each app image. Then, the relationship between selected features of app image and satisfactory range of device brightness is analyzed. Next, app images are categorized by using two features of average brightness of app image and distribution ratio of advanced colors that are related to satisfaction range of device brightness. Then, optimal device brightness for each category is selected by having the maximum frequency of satisfaction device brightness. Experimental results show that the categorized app images with optimal device brightness have high satisfaction ratio under various light conditions.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.141-147
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• 2015

The contrast of a display is generally evaluated by using the ratio of the minimum luminance to the maximum luminance of the display. However, this contrast ratio is not matched with perceived contrast because it uses only physical characteristic of display without considering human perceptual characteristics. In this paper, the proposed contrast measure that considers perceptually discriminable brightness within the range of display brightness is suggested. First, the range between the minimum and maximum brightness of display in CIECAM02 color space is calculated to measure the length of perceived brightness for the display. Next, brightness ranges which are perceptually same at each brightness level are determined by applying Weber-Fechner ratio and then, the number of brightness values within each brightness range is counted. Finally, perceptually discriminable brightness is defined as the sum of ratio between the number of brightness values in each brightness range and the perceptual contrast length of the display. In the experiments, preference test using various displays with random brightness patches is performed to evaluate perceived contrast. As a result, the proposed measure is more consistent with human perception than the previous contrast measures.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.129-137
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• 2010

There are a lot of multimedia functions getting included in mobile devices recently, not only simple audio but visual functions as well, such as video playing, game and web browsing. Such the visual multimedia functions brought the strong requirement for much bigger LCD Display and high resolution. And the brightness of LCD is also one of major requirements and it is required to be more bright. However, LCD brightness is limited to increase because of power consumption. It occupies nearly 30% of the whole system power. This thesis suggests an effective and simple method of adjusting the LCD backlight brightness, considering a characteristic of battery and user pattern.