• Journal of Korea Multimedia Society
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• v.12 no.9
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• pp.1217-1232
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• 2009

In this paper, we propose a semi-automatic 3D building reconstruction method using uncalibrated images which includes the facade of target building. First, we extract feature points in all images and find corresponding points between each pair of images. Second, we extract lines on each image and estimate the vanishing points. Extracted lines are grouped with respect to their corresponding vanishing points. The adjacency graph is used to organize the image sequence based on the number of corresponding points between image pairs and camera calibration is performed. The initial solid model can be generated by some user interactions using grouped lines and camera pose information. From initial solid model, a detailed building model is reconstructed by a combination of predefined basic Euler operators on half-edge data structure. Automatically computed geometric information is visualized to help user's interaction during the detail modeling process. The proposed system allow the user to get a 3D building model with less user interaction by augmenting various automatically generated geometric information.

• Journal of Internet Technology
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• v.20 no.5
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• pp.1535-1545
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• 2019

Recently, the diverse kinds of applications in multimedia computing have been developed for visual surveillance, healthcare, smart cities, and security. Video conferencing is one of core applications among multimedia applications. The Quality of Service of video conferencing is a major issue, because of limited network traffic. Video conferencing allow a large number of users to converse with each other. However, the huge amount of packets are generated in the process of transmitting and receiving the photographed images of users. Therefore, the number of packets in video conferencing needs to be reduced. Video conferencing can be conducted in virtual reality by sending only the control signals of virtual characters and showing virtual characters based on the received signals to represent the users, instead of the photographed images of the users, in real time. This paper proposes a method that determines representative photographed images by analyzing the collected photographed images of users, using KMedoids algorithm and a decision tree, and expresses the users based on the analyzed images. The decision tree used for video conferencing are generated automatically using the proposed method. Given that the behaviors in the decision tree is added or changed considering photographed images, it is possible to reproduce the decision tree by photographing the behavior of the user in real-time. In an experiment conducted, 63 consecutively photographed images were collected and a decision tree generated by using the silhouette images of the photographed images. Indices of the silhouette images were utilized to express a subject and one index was selected using a decision tree. The proposed method reduced the number of comparisons by a factor of 3.78 compared with the traditional method that uses correlation coefficient. Further, each user's image could be outputted by using only the control image table of the image and the index.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.727-731
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• 2009

In this paper, we propose a method to generate a free viewpoint image using multi-viewpoint images which are taken by cameras arranged circularly. In past times, we have proposed the method to generate a free viewpoint image based on Ray-Space method. However, with that method, we can not generate a walk-through view seen from a virtual viewpoint among objects. The method we propose in this paper realizes the generation of such view. Our method gets information of the positions of objects using shape from silhouette method at first, and selects appropriate cameras which acquired rays needed for generating a virtual image. A free viewpoint image can be generated by collecting rays which pass over the focal point of a virtual camera. However, when the requested ray is not available, it is necessary to interpolate it from neighboring rays. Therefore, we estimate the depth of the objects from a virtual camera and interpolate ray information to generate the image. In the experiments with the virtual sequences which were captured at every 6 degrees, we set the virtual camera at user's choice and generated the image from that viewpoint successfully.

• Journal of International Society for Simulation Surgery
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• v.3 no.2
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• pp.39-45
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• 2016

The augmented reality is the environment which consists of real-world view and information drawn by computer. Since the image which user can see through augmented reality device is a synthetic image composed by real-view and virtual image, it is important to make the virtual image generated by computer well harmonized with real-view image. In this paper, we present reviews of several works about computer vision and graphics methods which give user realistic augmented reality experience. To generate visually harmonized synthetic image which consists of a real and a virtual image, 3D geometry and environmental information such as lighting or material surface reflectivity should be known by the computer. There are lots of computer vision methods which aim to estimate those. We introduce some of the approaches related to acquiring geometric information, lighting environment and material surface properties using monocular or multi-view images. We expect that this paper gives reader's intuition of the computer vision methods for providing a realistic augmented reality experience.

• Journal of Korea Multimedia Society
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• v.11 no.6
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• pp.746-754
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• 2008

A 3D stereoscopic image is generated by interdigitating every scene with video editing tools that are rendered by two cameras' views in 3D modeling tools, like Autodesk MAX(R) and Autodesk MAYA(R). However, the depth of object from a static scene and the continuous stereo effect in the view of transformation, are not represented in a natural method. This is because after choosing the settings of arbitrary angle of convergence and the distance between the modeling and those two cameras, the user needs to render the view from both cameras. So, the user needs a process of controlling the camera's interval and rendering repetitively, which takes too much time. Therefore, in this paper, we will propose the 3D stereoscopic image editing system for solving such problems as well as exposing the system's inherent limitations. We can generate the view of two cameras and can confirm the stereo effect in real-time on 3D modeling tools. Then, we can intuitively determine immersion of 3D stereoscopic image in real-time, by using the 3D stereoscopic image preview function.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.4
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• pp.709-720
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• 2024

By inputting consumer satisfaction as an exogenous variable into the value-based adoption model, this study explored the factors that influence the user's intention to continue using image-centered generative AI. Briefly presenting the main results, first, enjoyment did not significantly affect perceived value, but usefulness had a positive effect on perceived value. Second, Fee and technicality had a negative effect on perceived value. Third, perceived value had a positive effect on consumer satisfaction and continuous use intention. Fourth, consumer satisfaction had a positive effect on continuous use intention. Based on the above results, it is important to recognize the usefulness of image-centered generated AI and enjoyment in the process of use in order to increase the user's intention to continue using image-centered generated AI, and at the same time, it will be important to increase the user's perceived value and satisfaction by minimizing the reasonable fee and complexity in the method of use at the level acceptable to the users.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.202-207
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• 2002

EOC (Electro-Optical Camera) of KOMPSAT-1 (Korea Multi-Purpose SATellite) has been producing land imageries of the world since January 2000. After image data are acquired by EOC, they are transmitted from satellite to ground via X-band RF signal. Then, EOC image data are generated and pass through radiometric and geometric corrections to generate standard products of EOC images. After radiometric correction on EOC image data, Modulation Transfer Function (MTF) compensation is applicable on EOC images with user's request for better image quality. MTF compensation is concerned with filtering EOC images to minimize the effect of degradations. For Image Receiving and Processing System (IRPE) at KOMPSAT Ground Station (KGS), Wiener filter is used in MTF compensation for EOC images. If the Pointing Spread Function (PSF) of EOC system is known, signal-to-noise power spectra ratio is the only factor in the determination of Wiener filter. In this paper, MTF compensation in IRPE at KGS is introduced and MTF compensated EOC 1R images are generated using Wiener filters with various signal-to-noise power spectra ratios. MTF compensated EOC 1R images are correlated with EOC 1R images for observing linearities between them. As a result, the effect of signal-to-noise power spectra ratio is shown on MTF compensated EOC 1R images.

• Journal of Broadcast Engineering
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• v.7 no.2
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• pp.168-180
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• 2002

This paper proposes a novel method to detect unauthorized copies of digital images. This copy detection scheme can be used as either an alternative approach or a complementary approach to watermarking. A test image is reduced to 8$\times$8 sub-image by intensity averaging, and the AC coefficients of its discrete cosine transform (DCT) are used to compute distance from those generated from the query image, of which a user wants to find copies. Copies may be Processed to avoid copy detection or enhance image quality. We show ordinal measure of DCT coefficients, which is based on relative ordering of AC magnitude values and using distance metrics between two rank permutations, are robust to various modifications of the original image. The optimal threshold selection scheme using the maximum a posteriori (MAP) criterion is also addressed.

• Journal of Information Processing Systems
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• v.19 no.6
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• pp.767-777
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• 2023

In modern society, user privacy is emerging as an important issue as closed-circuit television (CCTV) systems increase rapidly in various public and private spaces. If CCTV cameras monitor sensitive areas or personal spaces, they can infringe on personal privacy. Someone's behavior patterns, sensitive information, residence, etc. can be exposed, and if the image data collected from CCTV is not properly protected, there can be a risk of data leakage by hackers or illegal accessors. This paper presents an innovative approach to "machine learning based reversible chaotic masking method for user privacy protection in CCTV environment." The proposed method was developed to protect an individual's identity within CCTV images while maintaining the usefulness of the data for surveillance and analysis purposes. This method utilizes a two-step process for user privacy. First, machine learning models are trained to accurately detect and locate human subjects within the CCTV frame. This model is designed to identify individuals accurately and robustly by leveraging state-of-the-art object detection techniques. When an individual is detected, reversible chaos masking technology is applied. This masking technique uses chaos maps to create complex patterns to hide individual facial features and identifiable characteristics. Above all, the generated mask can be reversibly applied and removed, allowing authorized users to access the original unmasking image.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.2005-2021
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• 2014

This paper proposes a novel image authentication scheme, aiming at tampering detection for block truncation coding (BTC) compressed image. The authentication code is generated by using the random number generator with a seed, and the size of the authentication code is based on the user's requirement, with each BTC-compressed image block being used to carry the authentication code using the data hiding method. In the proposed scheme, to obtain a high-quality embedded image, a reference table is used when the authentication code is embedded. The experimental results demonstrate that the proposed scheme achieves high-quality embedded images and guarantees the capability of tamper detection.