• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.4 s.304
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• pp.59-68
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• 2005

This paper proposes a face recognition under varying poses using local area obtained by side-view pose normalization. General normalization methods for face recognition under varying pose have a problem with the information about invisible area of face. Generally this problem is solved by compensation, but there are many cases where the image is distorted or features lost due to compensation .To solve this problem we normalize the face pose in side-view to reduce distortion that happens mainly in areas that have large depth variation. We only use undistorted area, removing the area that has been distorted by normalization. We consider two cases of yaw pose variation and pitch pose variation, and by experiments, we confirm the improvement of recognition performance.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.7-16
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• 1998

The Scanora/sup (R)/ X-ray unit uses the principles of narrow beam radiography and spiral tomography. Starting with a panoramic overview as a scout image. multiple tomographic projections could be selected. This study evaluated the accuracy of spiral tomography in comparison to routine panoramic radiography for dental implant treatment planning. An experimental study was performed on a cadaver mandible to assess the accuracy of panoramic radiography and spiral tomography film images for measurement of metallic spheres. After radiographic images of the metallic spheres on the surgical stent were measured and corrected for a fixed magnification of radiographic images. following results were obtained. 1. In the optimal position of the mandible. the minimal horizontal and vertical distortion was evident in the panoramic radiography images. The mean horizontal and vertical magnification error in anterior sites was 5.25％ and 0.75％. respectively. The mean horizontal and vertical magnification error in posterior sites was 0.50％ and 1.50％. respectively. 2. In the displaced forward or in an eccentric position of the mandible. the magnification error of the panoramic radiography images increased significantly over the optimal position. Overall, the mean horizontal magnification error of the anterior site in the different positions changed dramatically within a range of -17.25％ to 39.00％, compared to the posterior range of -5.25％ to 8.50％. However, the mean vertical magnification error stayed with the range of 0.5％ to 3.75％ for all the mandibular positions. 3. The magnification effects in the tomographic scans were nearly identical for the anterior and posterior with a range of 2.00％ to 5.75％ in the horizontal and 4.50％ to 5.50％ in the vertical dimension, respectively. 4. A statistically significant difference between the anterior and posterior measurements was found in the horizontal measurements of the panoramic radiography images of the displaced forward and backward position of the mandible(P<0.05). Also a significant difference between the optimal panoramic and tomographic projections was found only in the vertical measurement(P<0.05).

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.6
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• pp.63-72
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• 2005

In this paper, we propose the bit-rate control algorithm for the block based image compression like H.263, H.263+ or MPEG-4. The proposed algorithm is designed to identify the quantization parameter set through the Lagrangian optimization technique based on the well-known linear source model. We set the Lagrangian cost function with the rates and distortion calculated from the linear source model. We calculate the quantization parameter set using the Vitervi algorithm to solve the Lagrangian optimization problem considering the Dquant method of H.263 and MPEG-4. The proposed algorithm improves the video quality by up to 1.5 dB compared with the TMN8 scheme, and is more effective in the video sources with dynamic activities than the consistent quality approaches.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1456-1461
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• 2003

Recently, the quantity of using information go on increasing geometric-progression. At the same time, the management of information is effected on the most organization's effective operation so that many user call for the powerful equipment which expound. access more information. As information searching technology is concentrated about the object of information based on a letter mainly, an effective searching technology for the object of multimedia such as a still image, a video and a sound must be studied. As a monitor of computer is 2-D, it difficult for one to grasp the whole aspect at a look glance like a library. Accordingly, some condition is necessary. First, it acquired the virtual video, turning a camera around by 30 degrees with a camera of 15mm lens, giving a warping and distortion. Second, it improved the books for user to search easily, adding to the video in existing books information system. The original text suggests some way which can embody the video searching technology under the base of personal computer.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.3
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• pp.187-192
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• 2012

This paper describes efficient H.264/AVC video scrambling methods for digital rights management. The proposed scrambling methods are to scramble level and suffix in entropy encoding and MVD in motion estimation of the H.264 video compression process. Other scrambling methods have been proposed but they degrade the compression efficiency or make it difficult to achieve real-time processing due to the large amount of computational efforts. Since the proposed scrambling methods resolve the drawbacks of other approaches, they do not cause image distortion and the original compression efficiency is maintained. We verified our scrambling methods and evaluated the performance by conducting several experiments with H.264 reference program. Finally, we implemented video player system using USB dongle in order to apply the proposed scrambling/descrambling methods to H.264 video compression.

• The KIPS Transactions:PartB
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• v.18B no.1
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• pp.1-10
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• 2011

Reversible watermarking inserts watermark into digital media in such a way that visual transparency is preserved, which enables the restoration of the original media from the watermarked one without any loss of media quality. It has various applications, where high capacity and high visual quality are major requirements. This paper presents a new effective multi-round embedding scheme for the differential histogram-based reversible watermarking that satisfies high capacity requirements of the application. The proposed technique exploits the row-column cross scanning to fully utilize the locality of images when multi-round embedding phase to the message inserted image. Through experiments using multiple kinds of test images, we prove that the presented algorithm provides 100% reversibility, effectiveness of multi-round embedding, and higher visual quality, while maintaining the induced-distortion low.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2372-2374
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• 2003

With 3-D vision measuring, camera calibration is necessary to calculate parameters accurately. Camera calibration was developed widely in two categories. The first establishes reference points in space, and the second uses a grid type frame and statistical method. But, the former has difficulty to setup reference points and the latter has low accuracy. In this paper we present an algorithm for camera calibration using perspective ratio of the grid type frame with different line widths. It can easily estimate camera calibration parameters such as focal length, scale factor, pose, orientations, and distance. But, radial lens distortion is not modeled. The advantage of this algorithm is that it can estimate the distance of the object. Also, the proposed camera calibration method is possible estimate distance in dynamic environment such as autonomous navigation. To validate proposed method, we set up the experiments with a frame on rotator at a distance of 1,2,3,4[m] from camera and rotate the frame from -60 to 60 degrees. Both computer simulation and real data have been used to test the proposed method and very good results have been obtained. We have investigated the distance error affected by scale factor or different line widths and experimentally found an average scale factor that includes the least distance error with each image. It advances camera calibration one more step from static environments to real world such as autonomous land vehicle use.

• Journal of Broadcast Engineering
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• v.23 no.2
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• pp.227-234
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• 2018

Recently, stitching techniques are used for obtaining wide FOV, e.g., panorama contents, from normal cameras. Despite many proposed algorithms, the no objective quality evaluation method is developed, so the comparison of algorithms are performed only in subjective way. The paper proposes a 'Delaunay-triangulation based objective assessment method' for evaluating the geometric and photometric distortions of stitched or warped images. The reference and target images are segmented by Delaunay-triangulation based on matched points between two images, the average Euclidian distance is used for geometric distortion measure, and the average or histogram of PSNR for photometric measure. We shows preliminary results with several test images and stitching methods for demonstrate the benefits and application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.338-343
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• 2004

In Block Matching Algorithm (BMA), a search pattern has a very important affect on the search time and the output quality. In this paper, we propose the HDS( Half Diamond Search) pattern based on the cross center-biased distribution property of a motion vector. At lust, the 4 points in the above, below, left, and right around the search center is calculated to decide the point of the MBD (Minimum Block Distortion). And an above point of the MBD is checked to calculate the SAD. If the SAD is less than the previous MBD, this process is repeated. Otherwise, the left and right points of MBD are calculated to decide the points that have the MBD between two points. These processes are repeated to the predicted direction for motion estimation. Experiments show that the speedup improvement of the proposed algorithm can be up to 23% while maintaining similar image quality.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2417-2426
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• 2014

Remote gaze tracking system calculates the gaze from captured images that reflect infra-red LEDs in cornea. Glint is the point that reflect infra-red LEDs to cornea. Recently, remote gaze tracking system uses a number of IR-LEDs to make the system less prone to head movement and eliminate calibration procedure. However, in some cases, some of glints are unable to spot. In this case, it is impossible to calculate gaze. This study examines patterns of glints that are difficult to detect in remote gaze tracking system. Afterward, we propose an algorithm to reconstruct positions of missing glints that are difficult to detect using other detected glints. Based on this algorithm, we increased the number of valid image frames in gaze tracking experiments, and reduce errors of gaze tracking results by correcting glint's distortion in the reconstruction phase.