• Title, Summary, Keyword: Median Filter

Search Result 376, Processing Time 0.057 seconds

Image Restoration by Lifting-Based Wavelet Domain E-Median Filter

  • Koc, Sema;Ercelebi, Ergun
    • ETRI Journal
    • /
    • v.28 no.1
    • /
    • pp.51-58
    • /
    • 2006
  • In this paper, we propose a method of applying a lifting-based wavelet domain e-median filter (LBWDEMF) for image restoration. LBWDEMF helps in reducing the number of computations. An e-median filter is a type of modified median filter that processes each pixel of the output of a standard median filter in a binary manner, keeping the output of the median filter unchanged or replacing it with the original pixel value. Binary decision-making is controlled by comparing the absolute difference of the median filter output and the original image to a preset threshold. In addition, the advantage of LBWDEMF is that probabilities of encountering root images are spread over sub-band images, and therefore the e-median filter is unlikely to encounter root images at an early stage of iterations and generates a better result as iteration increases. The proposed method transforms an image into the wavelet domain using lifting-based wavelet filters, then applies an e-median filter in the wavelet domain, transforms the result into the spatial domain, and finally goes through one spatial domain e-median filter to produce the final restored image. Moreover, in order to validate the effectiveness of the proposed method we compare the result obtained using the proposed method to those using a spatial domain median filter (SDMF), spatial domain e-median filter (SDEMF), and wavelet thresholding method. Experimental results show that the proposed method is superior to SDMF, SDEMF, and wavelet thresholding in terms of image restoration.

  • PDF

A study on Adaptive Multi-level Median Filter using Direction Information Scales (방향성 정보 척도를 이용한 적응적 다단 메디안 필터에 관한 연구)

  • 김수겸
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.28 no.4
    • /
    • pp.611-617
    • /
    • 2004
  • Pixel classification is one of basic image processing issues. The general characteristics of the pixels belonging to various classes are discussed and the radical principles of pixel classification are given. At the same time. a pixel classification scheme based on image direction measure is proposed. As a typical application instance of pixel classification, an adaptive multi-level median filter is presented. An image can be classified into two types of areas by using the direction information measure, that is. smooth area and edge area. Single direction multi-level median filter is used in smooth area. and multi-direction multi-level median filter is taken in the other type of area. What's more. an adaptive mechanism is proposed to adjust the type of the filters and the size of filter window. As a result. we get a better trade-off between preserving details and noise filtering.

A Fast Median Filter Algorithm for Noised Digital Image (가산잡음에 대한 고속 메디안 필터 알고리즘)

  • Kwon, Kee-Hong
    • Journal of the Korean Institute of Telematics and Electronics T
    • /
    • v.35T no.2
    • /
    • pp.13-19
    • /
    • 1998
  • The Median of a set of number is a number which partitions the given set. The specified numbers of a set partitions in one subset and in another subset. In Image Processing, The Sorting method of numbers of one subset equal to the previous Median Filtering. but The Sorting method of numbers of another subset not equal to in the other. In this paper, a fast two-dimentional Median Filtering Algorithm is proposed. The Algorithm designed in such a during the partitioning of the previous window are used. Test results obtained by running the Algorithm on IBM PC(586) are presented and its filtering. It is shown that the proposed Algorithm's processing time is faster and independent of the number of bits used to represent the data values.

  • PDF

A study on adaptive weighted median filter using edge information (에지정보를 이용한 적응적 가중메디안필터에 대한 연구)

  • Lee, Yong-Hwan;Park, Jang-Chun
    • The Transactions of the Korea Information Processing Society
    • /
    • v.6 no.10
    • /
    • pp.2830-2837
    • /
    • 1999
  • Image processing steps are consist of image acquisition, preprocessing, region, segmentation and recognition. But image corrupted commonly by noise reduction methods, many filters were proposed like mean filter, median filter, weighted median filter, Cheikh filter, and Kyu-cheol lee filter as spatial noise reduction filtering. We propose a new edge detection algorithm so that we find out edge existence and nonexistence. In non-edge area, we selectively apply weighted median filter based upon using information of difference value between weighted median filter's value and center pixel's value. As a result, we finally prove a better performance of noise reduction by applying adaptive weighted median filter and improvement of processing time through using simple algorithm.

  • PDF

A study on improvement of the weighted median filter in low noise (저잡음하에서 WM 필터의 개선에 관한 연구)

  • 이용환;서민형;우상근;박장춘
    • Proceedings of the Korean Information Science Society Conference
    • /
    • /
    • pp.467-468
    • /
    • 1998
  • Impulsive noise appears as black and/or white spots in an image. It is usually caused by errors during the image acquisition or transmission through communication channels. This paper presents a study on the impulsive noise reduction filter of digital image. A much more effective method for removing impulse noise is weighted median filtering. But it loses some information by changing center value with no condition. We propose some new technique to change center value with some conditions. In this paper, the performance of conditional weighted median filter is compared to the commonly used median filter, mean filter, max/min filter, and weighted median filter. A quantitative comparison is performed on MSE (Mean Square Error), RMSE (Root Mean Square Error), and SNR (Signal to Noise Ratio). Proposed conditional weighted median filter can yield better performance than regular filters.

  • PDF

Level order Recursive Median Filter by Spatial Histogram (공간 히스토그램을 이용한 레벨 순서별 Recursive Median Filter)

  • 조우연;최두일
    • Journal of the Institute of Electronics Engineers of Korea SP
    • /
    • v.41 no.6
    • /
    • pp.195-208
    • /
    • 2004
  • Histogram is a very useful method on various practical aspect. With increasing importance of simple calculation method and convenience, it became the basic method in digital image processing nowadays. However, basic limit of using histogram is losing spatial position information of pixels on image. This paper reanalyzes image by presenting histogram with spatial position information(spatial histogram). Also using that result, level order recursive median filter is realized. Presented recursive median filter showed much improved results on edge maintenance aspect compared to existing recursive median filter.

Modified Median Filter for Image Restoration in Salt and Pepper Noise Environments (Salt and Pepper 잡음 환경에서 영상 복원을 위한 변형된 메디안 필터)

  • Hong, Sang-Woo;Kim, Nam-Ho
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • /
    • pp.252-255
    • /
    • 2014
  • Image treatment is becoming mainstream as the demand for image restoration has drastically increased in the digital era. But in the process of acquiring, transmitting and treating video data, the salt and pepper noise damages the image. One of the major methods used for restoring images are SMF(standard median filter), CWMF(center weighted median filter) and SWMF(switching weighted median filter), but these filters all leave a bit to be desired in terms of removing noise and preserving edge. Therefore, a transformed median filter is suggested through the algorithm presented for the restoration of damaged images.

  • PDF

Performance evaluation of noise reduction algorithm with median filter using improved thresholding method in pixelated semiconductor gamma camera system: A numerical simulation study

  • Lee, Youngjin
    • Nuclear Engineering and Technology
    • /
    • v.51 no.2
    • /
    • pp.439-443
    • /
    • 2019
  • To improve the noise characteristics, software-based noise reduction algorithms are widely used in cadmium zinc telluride (CZT) pixelated semiconductor gamma camera system. The purpose of this study was to develop an improved median filtering algorithm using a thresholding method for noise reduction in a CZT pixelated semiconductor gamma camera system. The gamma camera system simulated is a CZT pixelated semiconductor detector with a pixel-matched parallel-hole collimator and the spatial resolution phatnom was designed with the Geant4 Application for Tomography Emission (GATE). In addition, a noise reduction algorithm with a median filter using an improved thresholding method is developed and we applied our proposed algorithm to an acquired spatial resolution phantom image. According to the results, the proposed median filter improved the noise characteristics compared to a conventional median filter. In particular, the average for normalized noise power spectrum, contrast to noise ratio, and coefficient of variation results using the proposed median filter were 10, 1.11, and 1.19 times better than results using conventional median filter, respectively. In conclusion, our results show that the proposed median filter using improved the thresholding method results in high imaging performance when applied in a CZT semiconductor gamma camera system.

Hybrid filter for noise reduction (잡음제거를 위한 하이브리드 필터)

  • Joh, Beom Seok;Kim, Young Ro
    • Journal of Korea Society of Digital Industry and Information Management
    • /
    • v.7 no.4
    • /
    • pp.133-139
    • /
    • 2011
  • In this paper, we propose a hybrid filter for noise reduction. The proposed method adjusts rational filtering direction according to an edge in the image using median filtered data. Rational filter modulates the coefficients of a linear lowpass filter to limit its action in presence of image details. By the ratio of polynomials in the input variables, rational filter reduces noise adaptively. Median filter is widely used to reduce impulse noise, but removes some details for highly corrupted images. Also, desirable details are removed when the window size is large. Our proposed algorithm combines rational filter and median filter. Thus, proposed method not only preserves edge, but also reduces noise in uniform region. Experimental results show that our proposed method has better quality than those by existing median and rational filtering methods.

Theoretical analysis of the properties of the pseudomedian filter

  • Lee, Dong-Ho
    • The Journal of the Acoustical Society of Korea
    • /
    • v.15 no.2E
    • /
    • pp.8-13
    • /
    • 1996
  • The pseudomedian filter was designed to be a computationally effecient alternative to the median filter. However, a thorough analysis ofter pseudomedian filter reveals some important differences between its response and that of the median filter. This paper develops some formal properties of the pseudomedian filter. The root signal analysis demonstrates the close relatonship between the median and pseudomedian filters while pointing out important and useful differences.

  • PDF