• Title/Summary/Keyword: Ringing Artifact

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The Evaluation of Images with Various Filters in I-131 SPECT/CT (I-131 SPECT/CT에서 Ringing Artifact 감소를 위한 다양한 Filter값의 적용)

  • Kim, Ha Gyun;Kim, Soo Mee;Woo, Jae Ryong;Oh, So Won;Lee, Jae Sung;Kim, Yu Kyeong
    • The Korean Journal of Nuclear Medicine Technology
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    • v.18 no.1
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    • pp.62-68
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    • 2014
  • Purpose: After I-131 therapy, SPECT/CT is useful in identifying location of thyroid remnants and metastasis of thyroid cancers. An excessive uptake of thyroid leads to a ringing artifact in the SPECT images. The aim of this study is to investigate and suggest a proper post filters to remove ringing artifact and produce better image quality. Materials and Methods: A low-cost, customized thyroid-mimicking phantom, consisting of an acrylic bottle and a hollow sphere was used for SPECT/CT Discovery (GE Healthcare, USA). It was filled with I-131 solution. The ratio of hollow sphere to background were varied as 50:1, 200:1, 1000:1 and 4000:1. Acquired images were reconstructed by OSEM (2 iterations, 10 subsets) with and without Evolution (resolution recovery correction, GE). Three different post-filters were applied; Butterworth (cut off: 0.38 to 0.58 with intervals of 0.05), Hanning (cut off: 0.8 to 1 with intervals of 0.05) and Gaussian (FWHM: 3 to 5 with intervals of 0.5) filters. Contrast, background variability, air area variability, and full width half maximum (FWHM) were compared. Results: Higher contrasts were obtained from the SPECT images with Evolution than without Evolution. In the case of images without Evolution, image distortion such as star artifact was generated. For all sphere-to-background ratio, the Butterworth filter showed better constrasts and FWHMs than other two filters, but the ringing artifact was still generated in all studies except 50:1 and it was decreased as cutoff value was increased. The ringing artifact didn't appear with Hanning and Gaussian filters at all studies, however constrats and FWHMs with Gaussian was worse than Hanning filter. For the images having ringing artifacts, the background variability and air area variability were increased. Conclusion: In this study, we suggested that it is desirable to use Hanning filter when the ringing artifact is generated and to use Butterworth filter when ringing artifact is not generated in I-131 SPECT.

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A Bilateral Filtering Based Ringing Elimination Approach for Motion-blurred Restoration Image

  • Wang, Weiqing;Wang, Weihua;Yin, Jiao
    • Current Optics and Photonics
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    • v.4 no.3
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    • pp.200-209
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    • 2020
  • We describe an approach that uses a bilateral filter to reduce the ringing artifact in motion-blurred restoration image. It takes into account the specific physical structure of the ringing artifact combined with the properties of the human visual system. To properly reduce the ringing artifact, each of the adjacent pixels is limited in a straight line which has a given direction. To protect the edges and the texture regions of an image, our algorithm divides the image into texture regions and flat regions, and the artifact reduction algorithm is only applied to the flat region. Finally, we use 8 typical images and 5 objective quality evaluation indices to evaluate our algorithm. Experimental results show that our algorithm can obtain better results in subjective visual effect and in objective image quality evaluation.

Algorithm to prevent Block Discontinuity by Overlapped Block and Manning Window (중첩 기반 연산과 Hanning Window를 이용한 블록 불연속 노이즈 방지 알고리즘)

  • Kim, Joo-Hyun;Jang, Won-Woo;Park, Jung-Hwan;Yang, Hoon-Gee;Kang, Bong-Soon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.9
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    • pp.1650-1657
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    • 2007
  • In this paper, we propose an Overlapped Block and an Hanning Window to prevent a Block Discontinuity when we use an algorithm to eliminate ringing artifact which is based on a block structure. The algorithm to eliminate ringing artifact operates with a block structure and 24-RGB data and is based on a modified K-means algorithm. The proposed overlapped block method is piled up one on another per an half of the size of unit-block when an input image is split into several unit-blocks. Therefore, we define a data unit as the unit-block of the block size, $16{\times}16$ pixels. We reconstruct the processed data units into the original form of input image by using an isotropic form of Hanning Window. Finally, in order to evaluate the performance of the abovementioned algorithms, we compare three image, an input image with ringing artifact, an image result obtained by conventional method (non-overlapped), and an image result obtained the proposed method.

Coding Artifact Reduction for Block-based Image Compression (블록 기반 영상 압축을 위한 부호화 결함 감소)

  • Wee, Young-Cheul
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.48 no.1
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    • pp.60-64
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    • 2011
  • In this paper, we propose a new post-processing technique that removes blocking and ringing artifacts in Block discrete cosine transformation (BDCT)-coded images using bilateral filtering. The selection of filter parameters is a key issue in the application of a bilateral filter because it significantly affects the result. An efficient method of selecting the bilateral filter parameters is presented. The experimental results show that the proposed approach alleviates the artifacts efficiently in terms of PSNR, MSDS, and SSIM.

The Filtering Method to Reduce Corner Outlier Artifacts in HEVC (Corner Outlier Artifacts를 감소시키기 위한 HEVC 필터링 방법)

  • Ko, Kyung-hwan
    • Journal of Broadcast Engineering
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    • v.22 no.3
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    • pp.313-320
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    • 2017
  • The In-loop filtering methods such as de-blocking filter and SAO(Sample Adaptive Offset) applied to the HEVC standard achieves coding efficiency and subjective quality improvement by reducing the blocking artifacts and the ringing artifacts. However, despite the use of In-loop filtering methods, the artifacts called a corner outlier occurring at the corner points of block boundaries are not removed. In this paper, the corner outlier artifacts are reduced by the detection, determination, and filtering processes on the corner outlier pixels. Experimental results show that the proposed method improves the subjective picture quality and slightly increases the coding efficiency in Inter prediction.

Ringing Artifact Removal in Image Restoration Using Wavelet Transform (웨이블릿 변환을 이용한 영상복원의 물결현상 제거 방법)

  • Youn, Jin-Young;Yoo, Yoon-Jong;Jun, Sin-Young;Shin, Jeong-Ho;Paik, Joon-Ki
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.45 no.6
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    • pp.78-87
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    • 2008
  • Digital image find own level core media in multimedia as image restoration technology fields, which remove degradation factor for image enhancement, have been growing. Linear space-invariant image restoration algorithm often introduce ringing artifacts near sharp intensity transition areas. This paper presents a new adaptive post-filtering algorithm for reducing ringing artifact. The proposed method extracts an edge map of the image using wavelet transform Based on the edge information, ringing artifacts are detected, and removed by an adaptive bilateral filter. Experimental results show that the proposed algorithm can efficiently remove ringing artifacts with edge preservation.

A Study of Regularized Iterative Postprocessing of Wavelet-compressed Images (웨이블릿 압축된 영상의 정칙화 기반 후처리에 관한 연구)

  • Jung, Jung-Hoon;Jung, Shi-Chang;Paik, JoonKi
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.36S no.11
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    • pp.44-53
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    • 1999
  • This paper proposes an algorithm that postprocesses wavelet-compressed images by using regularized iterative image restoration. First, an appropriate modeling the image degradation system for wavelet-compression system is needed. Then, the method which uses one of nonlinear functions as constraint in regularized iterative restoration is proposed in order to remove coding artifacts efficiently, such as ringing artifact and blocking artifact, resulted from loss of high frequency coefficients. Lastly, experimental results show superiority of proposed algorithm as compared with existing algorithm.

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An Effective Postprocessing Algorithm in Multimedia System (멀티미디어 시스템에서의 효율적인 후처리 알고리듬)

  • Park Kyung-Nam;Kim Seung-Jin;You Hyun-bea;Lee Kuhn-ll
    • Journal of Korea Multimedia Society
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    • v.7 no.11
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    • pp.1521-1530
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    • 2004
  • In this paper, we present effective quantization noise reduction algorithm using signal adaptive filter and linear combination between blocks in multimedia system. In the proposed method, all of the blocks are classified into low frequency blocks, high frequency blocks, and midrange blocks according to DCT coefficients. Ringing artifacts are shown in high frequency blocks. So ringing artifact reduction algorithm is performed in high frequency blocks using a signal adaptive filter. And the blocking artifact reduction is performed by replacing the pixel value of blocky blocks using linear combination between blocky block and remote unblocky block. The simulation results shows better performance in respective of the subjective and objective image quality than the conventional method.

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An Effective Postprocessing Algorithm for Block Encoded Images Using Adaptive Filtering and Interpolation (적응적 필터링과 보간법을 이용한 블록기반 압축영상의 효율적인 후처리 알고리듬)

  • Park, Kyung-Nam
    • Journal of Korea Society of Industrial Information Systems
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    • v.12 no.1
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    • pp.39-45
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    • 2007
  • In this paper, we present a new postprocessing algorithm using interpolation and signal adaptive filter according to the each block characteristic which is acquired in block classification process. We applied blocking artifact reduction algorithm for four neighbor low frequency block and ringing artifacts is removed with preserving edges by applying a signal adaptive filter in high frequency block based on edge map. The computer simulation results confirmed a better performance by the proposed method in both the subjective and objective image qualities.

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Image Enhancement Using The Contrast Sensitivity Function (Contrast Sensitivity 함수를 이용한 영상화질 개선 방법)

  • Bang, Seangbae;Kim, Wonha
    • Journal of Broadcast Engineering
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    • v.20 no.2
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    • pp.238-247
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    • 2015
  • We develop the signal processing method for adaptive implementing direction of signal and the frequency sensitivity of human visual system(HVS). Existing multibnad energy scaling method makes ringing artifact because it does not consider signal direction. To solve this problem, we use block gradient for signal direction in addition to existing method. And we use the fact that frequency component of signal is more sensitive than value of signal over human eyes. we enhance the signal according to contrast sensitivity function(CSF) which is the model of frequency sensitivity of human eye. Compared that the existing analysis models only improve the efficiencies in the existing systems, the developed method can process the image signals to be more desirable and suitable to HVS.