• Journal of Platform Technology
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• v.12 no.3
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• pp.16-26
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• 2024

Videos shot underwater are known to have significant color distortion. Typical causes are backscattering by floating objects and attenuation of red colors in proportion to the depth of the water. In this paper, we aim to analyze color correction performance and color distortion patterns for images taken underwater. Backscattering and attenuation caused by suspended matter will be discussed in the next study. In this study, based on the DeepSeeColor model proposed by Jamieson et al., we verify color correction performance and analyze the pattern of color distortion according to changes in water depth. The input images were taken in the US Virgin Islands by Jamieson et al., and out of 1,190 images, 330 images including color charts were used. Color correction performance was expressed as angular error using the input image and the correction image using the DeepSeeColor model. Jamieson et al. calculated the angular error using only black and white patches among the color charts, so they were unable to provide an accurate analysis of overall color distortion. In this paper, the color correction error was calculated targeting the entire color chart patch, so an appropriate degree of color distortion can be suggested. Since the input image of the DeepSeeColor model has a depth of 1 to 8, color distortion patterns according to depth changes can be analyzed. In general, the deeper the depth, the greater the attenuation of red colors. Color distortion due to depth changes was modeled in the form of scale and offset movement to predict distortion due to depth changes. As the depth increases, the scale for color correction increases and the offset decreases. The color correction performance using the proposed method was improved by 41.5% compared to the conventional method.

• The Journal of Korean Society for Radiation Therapy
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• v.11 no.1
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• pp.43-48
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• 1999

Purpose : For practical application of the MR image for stereotactic radiosurgery, the target point achieved by acquisition of MR image in a relatively homogeneous phantom has to agree with the actual isocenter of irradiation in real radiosurgery and the amount of distortion of the MR image should be known. Materials and Methods : A dosimetric film with a random target point was inserted into a radish vertically and horizontally on axis Z and they were fixed with a headring. After image acquisition by stereotactic radiosurgery planning system, we achieved stereotactic coordinate of the target point and examined irradiation using the coordinate acquired as isocenter. After the irradiation, the film in the radish was developed and processed and the degree of coincidence between the target point marked on the film and the center of the radiation distribution. In order to measure the degree of distortion of the MR image in a different way, an acryl phantom was made and punctures were made at intervals of 1 cm and a drop of oil was dropped into it. Then, it was inserted into the radish vertically and horizontally on axis Z to acquire the MR image. Each coordinate was achieved and the estimation of distortion of MR image was made both in vertical and horizontal directions Results : The film from the radio was developed and for the one inserted vertically on axis Z, there was a good coincidence in the discrepancy between the target point marked on the film and the center of the radiation distribution. For the one inserted horizontally, the discrepancy between them was under 0.5 mm. As a result of estimating distortion of MR image using acryl, the discrepancy was under 0.45 mm in the case of the phantom inserted vertically on axis Z, and that of the one inserted horizontally was 1.4 mm. Conclusion : We were able to confirm good coincidence in homogeneous phantom in actual treatment position of radiosurgery using the MR image and the discrepancy measured in the analysis of distortion of the MR image did not exceed the permissible level. Therefore, it was evident the system of the hospital is suitable for radiosurgery using MR image.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.448-457
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• 2004

As computer Programs for cephalometric analysis were developed in diagnosis & treatment planning, digital imaging of film-based cephalograms came to be needed. When a digital camera is used, a problem encountered the image distortion produced according to the focal length, which causes errors in indentifying landmarks. In addition, changes in the image size and compression ratio will inevitably produce a low quality image, causing errors in identifying landmarks. Hence. we have found the focal length producing the least image distortion when digital imaging the film-based cephalograms and the minimal digital camera setting which helps to identify the correct landmarks using the COOLPIX4500 digital camera (Nikon, Japan). The results were as follows The image distortion was minimized at a focal length of 16.4mm (79.4mm when converted into a 35mm film camera) when digital imaging the film-based cephalograms. When wide imaging, with a focal length of under IS.4mm, barrel distortion was found and when tole imaging. with a focal length of over 15.4mm pincushion distortion was found. The minimal digital camera setting was $2272{\times}1704$ pixel at normal (1/8) compression from which we can identify the correct landmarks at the same level as tracing the film-based cephalograms manually. As a result. when digital imaging the film-based cephalograms, using a COOLPIX4500 digital camera (Nikon, Japan), the focal length should be 16.4mm the pixel image size over $2272{\times}1704$, and the compression ratio over normal (1/8).

• Journal of the Korean Society of Costume
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• v.54 no.3
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• pp.145-158
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• 2004

In modern art, body appears as artistic performer, material or producer. and is expressed as' social environment body' which is changed in the relationship with its society and culture. The correlation between body and clothing image appears in 'body as expression object' which directly borrows human body or sets up a section of human body, 'body as medium' in which clothing substitutes body, and 'body as image' in which image of body reappears along with clothing. The results of analysis are as follows : First, 'image of expansion and exaggeration' to expand the influence of clothing thereby disclosing illusion of material civilization prevalent in our society, and make metaphor of dwarfish human's lurking fear by transforming and exaggerating human body. Second, 'image of restriction and suppression' to express the loss of humanity, power and restriction of modern society with fixing and cruelty of body image through clothing which disregard body function. Third, 'image of open and fluidity to criticize the extinction of values of human existence and standardized figure of our society by reducing three-dimensional clothing and body to untypical form or introducing the image of absent of human body to clothing. Fourth, 'image of reversion and paradox' to express practical clothing object with unwearable material, or cause confusion of sex and identity by expressing dual aspects of body at the same time. In this study, which is focused on correlation between body and clothing and the meaning of them, I realized that, even though artistic clothing expressed image of distortion and deformation of human existence as essential subject of body, they, in most contents, were used as medium of communication to rediscover human dignity and identity, and consisted of a series of metaphoric network of meanings satirizing aspects of our society.

• The Journal of the Korea Contents Association
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• v.6 no.12
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• pp.21-28
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• 2006

In a face detection system based on template matching, histogram equalization or log transform is applied to an input image for the intensity normalization and the image improvement. It is known that they are noneffective in improving an image with intensity distortion by illumination variation. In this paper, we propose an efficient image improvement method using a simple regression analysis combined with a bilateral symmetry average for images with intensity distortion by illumination variation. Experimental results show that our method delivers the detection performance better than previous methods and also remarkably reduces the number of face candidates.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.809-815
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• 2014

The co-bonded dissimilar composite under a wide range of temperature change shows thermal distortion due to the differences in thermal expansion characteristics of the composite materials. Analysis of the thermal expansion characteristics of each composite is required for the design of co-bonded dissimilar composite structure with considering the shape distortion during the manufacturing process. In this work, digital image correlation (DIC) technique is introduced for measuring the thermal distortion characteristics of co-bonded dissimilar composite specimen, carbon/epoxy and silica/phenolic. The thermal distortion of co-bonded dissimilar composite specimen is numerically estimated and compared with the experiments. The estimated results is successfully validated using the measured results.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.49-59
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• 2012

Throughout developing digital technology, reproduction of image is growing better day by day. And at the same time, diverse image editing softwares are developed to manage images easily. In the process of editing images, those programs could delete or modify EXIF files which have the original image information; therefore images without the origin source are widely spread on the web site after editing. This matter could affect analysis of images due to the distortion of originality. Especially in the court of law, the source of evidence should be expressed clearly; therefore digital image EXIF file without deletion or distortion could not be the objective evidence. In this research, we try to trace the identification of a digital camera in order to solve digital images originality, and also we focus on lens distortion correction algorism which is used in digital image processing. Lens distortion correction uses mapping algorism, and at this moment it also uses interpolation algorism to prevent aliasing artifact and reconstruction artifact. At this point interpolation shows the similar mapping pattern; therefore we want to find out the interpolation evidence. We propose a minimum filter algorism in order to detect interpolation pattern and adjust the same minimum filter coefficient in two areas; one has interpolation and the second has no interpolation. Throughout DFT, we confirm frequency character between each area. Based on this result, we make the final detection map by using differences between two areas. In other words, thereby the area which has the interpolation caused by mapping is adjusted using minimum filter for detection algorism; the second area which has no interpolation tends to different frequency character.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.7 no.2
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• pp.45-51
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• 1989

Lens distortion would produce image displacement, therefore correction of lens distortion is required urgently to improve accuracy of results in photogrammetry. The objective of this study is to find out lens distortion coefficients versus focussing distance on non-metric and metric camera and to investigate propriety of application of lens distortion coefficients to three dimensional analysis. Analytical plumb line method which needs not perform control survey and space resection and requires only one photograph was used in order to get lens distortion coefficients. As the result of this study, the coefficients of radial and tangential distortion change as focussing distance changes, and consequently it is reasonable to apply the eigenvalues of lens distortion coefficients according to focussing distance. When these coefficients were applied to actual measurement, standard errors decreased about 30% or 76% remarkably.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.2
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• pp.73-86
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• 2009

This paper proposes a new data hiding scheme for binary image authentication with minimizing the distortion of host image. Based on the Hamming-Code-Based data embedding algorithm, the proposed scheme makes it possible to embed authentication information into host image with only flipping small number of pixels. To minimize visual distortion, the proposed scheme only modifies the values of the flippable pixels that are selected based on Yang et al's flippablity criteria. In addition to this, by randomly shuffling the bit-order of the authentication information to be embedded, only the designated receiver, who has the secret key that was used for data embedding, can extract the embedded data. To show the superiority of the proposed scheme, the two measurement metrics, the miss detection rate and the number of flipped pixels by data embedding, are used for the comparison analysis between the proposed scheme and the previous schemes. As a result of analysis, it has been shown that the proposed scheme flips smaller number of pixels than the previous schemes to embed the authentication information of the same bit-length. Moreover, it has been shown that the proposed scheme causes smaller visual distortion and more resilient against recent steg-analysis attacks than the previous schemes by the experimental results.

• Korean Journal of Remote Sensing
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• v.19 no.6
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• pp.431-445
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• 2003

In this paper, we experimentally investigated the precision of 3D positioning using 4S-Van images in photograrmmetric perspective. The 3D calibration target was built over building facade outside and was captured separately by two CCD cameras installed in 4S-Van. After then, we determined the interior orientation parameter for each CCD camera through self-calibration technique. With the interior orientation parameter computed, the bundle adjustment was performed to obtain the exterior orientation parameters simultaneously for two CCD cameras using calibration target image and object coordinates. The reverse lens distortion coefficients were computed and acquired by least squares method so as to introduce lens distortion into epipolar line. It was shown that the reverse lens distortion coefficients could transform image coordinates into lens distorted image coordinates within about 0.5 pixel. The proposed semi-automatic matching scheme incorporated with lens distorted epipolar line was implemented with scene images captured by 4S-Van in moving. The experimental results showed that the precision of 3D positioning from 4S-Van images in photograrmmetric perspective is within 2cm in the range of 20m from the camera.