• Journal of Korea Multimedia Society
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• v.13 no.4
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• pp.535-546
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• 2010

Digital images have undesired color casts due to various illumination conditions and intrinsic characteristics of cameras. Since the color casts in the images deteriorate performance of color representations, color correction is required for further analysis of images. In this paper, an algorithm for detection and removal of color casts is presented. The proposed algorithm consists of four steps: retrieving similar image using color by correlation, extraction of near neutral color regions, kernel density estimation, and removal of color casts. Ambiguities in near neutral color regions are excluded based on kernel density estimation by the color by correlation algorithm. The method determines whether there are color casts by chromaticity distributions in near neutral color regions, and removes color casts for color constancy. Experimental results suggest that the proposed method outperforms the gray world algorithm and the color by correlation algorithm.

• Communications of Mathematical Education
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• v.29 no.1
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• pp.91-110
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• 2015

The purpose of this study is to investigate the understanding of pi of elementary gifted students and explore improvement direction of teaching pi. The results of this study are as follows. First, students understood insufficiently the property of approximation, constancy and infinity of pi from the fixation on 'pi = 3.14'. They mixed pi up with the approximation of pi as well. Second, they had a inclination to understand pi as algebraic formula, circumference by diameter. Third, few students understood the property of constancy and infinity of pi deeply. Lastly, the discussion activity provided the chance of finding the idea of the property of approximation of pi. In conclusion, we proposed several methods which improve the teaching of pi at elementary school.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.93-96
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• 2015

The aim of the estimation of disparity map is to find the corresponding pixels from similar two or more images. However, it is a difficult problem to get precise and consistent disparity under a variety of real world situations. In other words, the color values of stereo images are easily influenced by radiometric properties such as illumination direction, illumination color, and camera exposure. Therefore, conventional stereo matching methods can have low performances under radiometric conditions. In this paper, we propose an approaching of disparity map estimation that is reliable in controlling various radiometric variations close to the real environment. This method is motivated by following constancy. Even though each other has different radiometric property in stereo images, intensity of pixels of object have general constancy in specific block. Experimental results show that the proposed method has better performances compared to the comparison group under different radiometric conditions between stereo images. Consequentially, the proposed method is able to estimate the disparity map in stable under various radiometric variations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3207-3213
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• 2011

Most methods of color constancy, which is the ability to determine the object color regardless of the scene illuminant, have failed to meet our expectation of their performance especially about low-illuminated scenes. Some methods with high performance need to be developed, but we must, above all else, obtain experimental images for analyzing the required circumstances or evaluating the methods. Therefore, the paper produces new sets of images so that they can be used in the development of color constancy methods suitable for low-illuminated scenes. These sets are composed of two parts: one part of images which are synthesized with spectral power distribution(SPD) of illuminants, spectral reflectance curve of reflectances, and sensor response functions of camera; the other part of images where the intensity of each image is adjusted at the uniform rate. In an experiment, the use of the sets takes an advantage that its result images are analyzed and evaluated quantitatively as their ground truth data are known in advance.

• Science of Emotion and Sensibility
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• v.25 no.1
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• pp.79-90
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• 2022

IThe perception of sub-second duration through the visual sensory system is affected by non-temporal characteristics (factors other than the duration of the stimulus). However, studies have shown that if distance information is abundant and size constancy maintained, the duration of the target is constantly perceived. The current study examined the relationship between size and time perception constancy in a three-dimensional environment with limited distance information. A device was constructed to limit the participants' bilateral and monocular cues. This prevented participants from maintaining size constancy, resulting in size illusions that could not accurately perceive physical size. In Experiment 1, the size of the physical stimulus of reference and test stimuli were the same at all viewing distances. The results suggest that, despite the same physical size, stimuli with close observations were perceived to be greater and lasted longer. In Experiment 2, the retinal size of the reference stimuli and test stimuli was controlled equally at all viewing distances. As a result, although the physical size of the stimuli increased as the observation increased, the perceived size of all the stimuli was the same. Therefore, the duration of the target was constantly perceived at all viewing distances. The results of this study demonstrate that even when distance information is limited, time perception is affected by the perceived size of the object. It also suggests that when rich distance information exists, the duration of the object can be constantly perceived even if the observation distance varies.

• Journal of the Korean Mathematical Society
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• v.41 no.6
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• pp.1007-1021
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• 2004

In this paper, we study rotation surfaces in the Minkowski 3-dimensional space with pointwise 1-type Gauss map and obtain by the use of the concept of pointwise finite type Gauss map, a characterization theorem concerning rotation surfaces and constancy of the mean curvature of certain open subsets on these surfaces.

• Journal of the Semiconductor & Display Technology
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• v.5 no.2 s.15
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• pp.15-18
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• 2006

This paper presents a optimizing algorithm getting through analyzing a image improvement algorithm using retinex theory. Improving a existing retinex theory's slow process speed, our proposal is that it controls a small filter size of surrounding function by comparing with original algorithm. So slow process speed decreased drastically. For filling a short of lighting information by small filter, we also selected gray image as a forth channel. Using the color constancy, we got fast process time like linear color correction and could do comfortable auto color rectification according to other images.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.6
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• pp.383-389
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• 2016

This paper presents a novel automatic white balance (AWB) algorithm for consumer imaging devices. While existing AWB methods require reference white patches to correct color, the proposed method performs the AWB function using only an input image in two steps: i) white point detection, and ii) color constancy gain computation. Based on the dark channel prior assumption, a white point or region can be accurately extracted, because the intensity of a sufficiently bright achromatic region is higher than that of other regions in all color channels. In order to finally correct the color, the proposed method computes color constancy gain values based on the Y component in the XYZ color space. Experimental results show that the proposed method gives better color-corrected images than recent existing methods. Moreover, the proposed method is suitable for real-time implementation, since it does not need a frame memory for iterative optimization. As a result, it can be applied to various consumer imaging devices, including mobile phone cameras, compact digital cameras, and computational cameras with coded color.

• Journal of Broadcast Engineering
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• v.1 no.1
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• pp.74-83
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• 1996

In this paper, an effective color image retrieval algorithm is proposed based on the graph representation. Also we propose a color constancy algorithm to remove the effect of illumination change. Illumination condition of an image can be transformed to that of reference image using the proposed color constancy algorithm, so that the effect of dirrerent lighting is significantly alleviated. Then, we represent a color image as a graph with several nodes and edges in the histogram space, and finally two images are matched by compared two graphs representing them. The simulation results show that the proposed 3-step algorithm performs well for various conditions, including different lighting, translation, rotation, and scaling of the object in the image. In addition, the proposed algorithm is very fast compared to the geometry-based matching technique.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.10
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• pp.5112-5129
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• 2019

Image enhancement is a challenging problem in the field of image processing, especially low-light color images enhancement. This paper proposed a robust and comprehensive enhancement method based several points. First, the idea of bright channel is introduced to estimate the illumination map which is used to attain the enhancing result with Retinex model, and the color constancy is keep as well. Second, in order eliminate the illumination offsets wrongly estimated, morphological closing operation is used to modify the initial estimating illumination. Furthermore, in order to avoid fabricating edges, enlarged noises and over-smoothed visual features appearing in enhancing result, a multi-scale closing operation is used. At last, in order to avoiding the haloes and artifacts presented in enhancing result caused by gradient information lost in previous step, guided filtering is introduced to deal with previous result with guided image is initial bright channel. The proposed method can get good illumination map, and attain very effective enhancing results, including dark area is enhanced with more visual features, color natural and constancy, avoiding artifacts and over-enhanced, and eliminating Incorrect light offsets.