• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.907-910
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• 1998

In this paper, we present a comparative performance analysis of several blocking artifact reduction algorithms. For the performance analysis, we propose a block boundary region classification algorithm which classifies each horizontal and vertical block boundary into four regions using brightness change near the block boundary. The PSNR performance of each algorithm is compared. The MSE according to each block boundary region is also compared. Experimental results show that the wavelet transform based blocking artifact reduction algorithms have better performance over the other methods.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.461-464
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• 2003

This paper proposes the multi-level vector error diffusion for smear artifact reduction in the boundary regions. Smear artifact mainly results from a large accumulation of quantization error. Accordingly, to reduce these artifacts, the proposed method excludes the large quantization error in the error diffusion process by comparing the magnitude of the error vector with predetermined first threshold. In addition, if the vector norm of the difference between the error adjusted input vector and the primary co]or that has minimum vector norm for the error adjusted input vector is larger than second threshold, the error is excluded. As a result, the proposed method reduce smear artifact in the boundary region and produces visually pleasing halftone pattern.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.5
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• pp.318-326
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• 1991

A Quantizer reconstruction level control method for block artifact reduction in DCT image coding is described. In our scheme, quantizer reconstruction level control is obtained by adding quantization level step size to the optimum quantization level in the direction of reducing the block artifact by minimizing the mean square error(MSE) and error difference(EDF) distribution in boundary without the other additional bits. In simulation results, although the performance in terms of signal to noise ratio is degraded by a little amount, mean square of error difference at block boundary and mean square error having relation block artifact is greatly reduced. Subjective image qualities are improved compared with other block artifact reduction method such as postprocessing by filtering and trasform coding by block overlapping. But the addition calculations of 1-dimensional DCT become to be more necessary to coding process for determining the reconstruction level.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10B
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• pp.1921-1936
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• 1999

In this paper, we analyze the blocking artifact in block transform-coded images and propose a classification algorithm which classifies each horizontal and vertical block boundary into four regions of EQ, BA, EE, and AE according to the characteristics of the blocking artifact. We also compare the performance of several blocking artifact reduction methods which can reduce blocking artifact in block transform-coded images well. As the blocking artifact reduction methods, the LOT, Kim's wavelet transform-based method, Yang's POCS, Paek's POCS, and Jang's CM have been selected. Experimental results show that each horizontal and vertical block boundary classified by using the proposed classification algorithm yields different characteristics of discontinuities due to the blocking artifact according to the classified region. It is also shown that the blocking artifact reduction methods using wavelet transform yield better performance over the other methods.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.111-120
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• 2004

This paper proposes a vector error diffusion method for smear artifact reduction in the boundary region. This artifact mainly results from a large accumulation of quantization errors. In particular, color bands with a smear artifact, the width of a few pixels appear along the edges. Accordingly, to reduce this artifact, the proposed halftoning process excludes the large accumulated Quantization error by comparing the vector norms and vector angles between the error-corrected vector and eight primary color patches. When the vector norm of the error corrected vector is larger than those of eight primary color patches, the quantization error vector is excluded from the quantization error distribution process. In addition, the quantization error is also excluded when the angle between eight primary color patches and error corrected vector is large. As a result, the proposed method enables a visually pleasing halftone pattern to be generated by all three color separations into account in a device- independent color space and reduces smear artifact in the boundary regions.

• Journal of Biomedical Engineering Research
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• v.19 no.6
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• pp.585-593
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• 1998

In Fourier magnetic resonance imaging (MRI), the number of phase encoded signals is often reduced to minimize the duration of the studies and maintain adequate signal-to-noise ratio. However, this results in the well-known truncation artifact, whose effect manifests itself as blurring and ringing in the image domain. In this paper, we propose a new regularization method in the context of a Bayesian framework to reduce truncation artifact. Since the truncation artifact appears in t도 phase direction only, the use of conventional piecewise-smoothness constraints with symmetric neighbors may result in the loss of small details and soft edge structures in the read direction. Here, we propose more elaborate forms of constraints than the conventional piecewise-smoothness constraints, which can capture actual spatial information about the MR images. Our experimental results indicate that the proposed method not only reduces the truncation artifact, but also improves tissue regularity and boundary definition without oversmoothing soft edge regions.

• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.977-984
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• 2003

In this paper, we propose an image enhancement algorithm for panoramic infrared image. This method divides a panoramic infrared image into disjoint subimages and performs the contrast stretch for subimages using statistical characteristics of each subimage. But these cause blocking artifact in boundary regions of neighboring subimages which different to the statistical characteristic. To remove blocking artifact, we perform the contrast stretch for subimage's boundary regions using statistical characteristics of horizontally neighboring subimages. Experimental results show that the proposed method effectively improves their appearance to human viewers.

• Journal of Korea Multimedia Society
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• v.17 no.7
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• pp.838-848
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• 2014

In this paper, we conducted a cause analysis on boundary artifacts in image deconvolution. Results of the cause analysis show that boundary artifacts are caused not only by a misuse of boundary conditions but also by no use of the normalized backprojection. Results also showed that the correct use of boundary conditions does not necessarily remove boundary artifacts. Based on these observations, we suggest not to use any specific boundary conditions and to use the normalized backprojector for boundary artifact-free image deconvolution.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.3
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• pp.30-41
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• 2011

In order to obtain more clear x-ray images, an antiscatter grid, which can absorb the scattered rays, is employed. In the high-resolution direct digital radiography, however, the artifacts due to the grid are visible. In this paper, within the methods of obtaining x-ray digital images by employing the rotated grids for the facility of grid artifact reduction, the previous work, where the frequencies of the artifact components on the boundary, is further analyzed and extended, and a min-max optimization for a given grid density is proposed. For practical grid densities, appropriate grid angles are provided and a grid artifact reduction algorithm is proposed for the appropriate grid angles. The proposed algorithm is tested for real x-ray digital images with a comparison, and can remove the grid artifacts while maintaining the resolution of the original image.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.755-758
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• 2001

In this paper. Ive propose a postprocessing technique based on the theory of projection on convex sets(POCS) to reduce the blocking artifacts in HDTV decoded images. In BDCT of HDTV. the image is divided into a grid of non-overlapped 8 ${\times}$ 8 blocks. and then each block is coded separately. A block which is located one pixel apart from the grid of BDCT will include the boundary of the original 8 ${\times}$ 8 block. If the blocking artifact is Introduced alone the block boundary. this block will have different frequency characteristic from that of the original block. Thus, a comparison of frequency characteristics of these two overlapping blocks can detect the undesired high-frequency components mainly caused by the blocking artifact. By eliminating these undesired high-frequency components adaptively, robust smoothing projection operator can be obtained. Simulation results with real image sequences indicate that the proposed method performs better than conventional algorithms.