switching bilateral filter with a texture noise detector for universal noise removal
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Switching Bilateral Filter With a Texture/Noise Detector for Universal Noise Removal. Chih-Hsing Lin, Jia-Shiuan Tsai, and Ching-Te Chiu Transactions on: Image Processing, IEEE Journals 2010. Outline. Introduction Sorted Quadrant Median Vector for Noise Detection Noise models

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switching bilateral filter with a texture noise detector for universal noise removal

Switching Bilateral Filter With a Texture/Noise Detector for Universal Noise Removal

Chih-Hsing Lin, Jia-Shiuan Tsai, and Ching-Te Chiu

Transactions on: Image Processing, IEEE Journals 2010

outline
Outline
  • Introduction
  • Sorted Quadrant Median Vector for Noise Detection
    • Noise models
    • Definition of Sorted Quadrant Median Vector (SQMV)
    • Features of SQMV
    • Edge/Texture identification with the clusters of SQMV
    • Reference median
  • Switching Bilateral Filter
    • Switching scheme
    • Noise detector design
    • Switching bilateral filter
  • Experimental Results
  • Conclusions
introduction
Introduction
  • Gaussian noise: a zero-mean Gaussian distribution.
    • Effective filter: linear filters (ex: averaging)
    • Side effect: blurring
  • Impulse noise: replacing a portion of an image pixels with noise values.
    • Effective filter: nonlinear filters (ex: median)
  • In this paper, we propose a universal noise removal filter based upon the “detect and replace” methodology.
noise models
-Noise models
  • The Impulse noise corrupted pixel ui,j:
    • Salt-and-pepper: ni,jonly takes values of Lmin or Lmax.
    • Uniform impulse: ni,jtakes random values from the interval [Lmin , Lmax]with a uniform distribution.
  • The Gaussian noise corrupted pixelui,j:
  • In this paper, mixed impulse and Gaussiannoiseis considered, and the Gaussian noise is independent of impulse noise.
sorted quadrant median vector for noise detection
Sorted Quadrant Median Vector for Noise Detection

The processing window size is too small.

  • Motivation of the Noise Detection Scheme:
    • Existing two-state noise detectors fail in several conditions[9][17].
    • The central pixel of (a)(b)identified as noise-freepixel.
    • The medians of(c) stillsimilar.

[9] T. Chen and H. R. Wu, “Adaptive impulse detection using center-weighted median filters,” IEEE Signal Process. Lett., vol. 8, no. 1, pp. 1–3, Jun. 2001.

[17] P. E. Ng and K. K. Ma, “A switching median filter with boundary discriminative noise detection for extremely corrupted images,” IEEE Trans. Image Process., vol. 15, no. 6, pp. 1506–1516, Jun. 2006.

definition of sorted quadrant median vector sqmv
-Definition of Sorted Quadrant Median Vector (SQMV)
  • To overcome the problems, we propose a sorted quadrant median vector (SQMV):
    • For a (2N+1) *(2N+1) window we divide the window into four (N+1)*(N+1) subwindows.
    • In the case N = 2:
definition of sorted quadrant median vector sqmv1
-Definition of Sorted Quadrant Median Vector (SQMV)
  • The set of points can be expressed as:
    • For (2N+1) *(2N+1) window:
    • For (N+1) *(N+1) subwindows:
    • Where the SQMV is defined as:
      • SQM1, SQM2, SQM3 and SQM4 are the medians m1, m2, m3, and m4 sortedin an ascending order.
edge texture identification with the clusters of sqmv
-Edge/Texture identification with the clusters of SQMV
  • The differencebetween two boundary values:

ρ lies in the interval [25–40]

reference median
-Reference median
  • In “without edge” or “weak edge” cases, the reference median (SQMR) for xij is the average of SQM2 and SQM3 (major cluster).
  • In “edge or texture” case, decide which cluster the current pixel xij falls into by dav:
reference median1
-Reference median
  • The pixel selection of x1~x4:
  • Thereference median (SQMR)in each case:

Even if complextexture , the filtering

result would be less artificial.

“without edge” or “weak edge”

“edge or texture”

switching bilateral filter
Switching Bilateral Filter
  • Bilateral Filter:
    • xi,j: the current pixel ̶yi,j: the filtered pixel
    • xi+s,j+t: he pixels in (2N+1)*(2N+1) window
switching scheme
-Switching scheme
  • In the switching scheme, we the noise detector searches for noisy pixels and tries to distinguish them from uncorruptedones.
  • The filtered image is defined as follows:
    • S1 and S2: the binary control signals generated by the noise detector.
noise detector design
-Noise detector design
  • The noise detection :
    • The threshold:
      • For salt-and-pepperimpulse noise: [Tk1 Tk2] =[3015]
      • For uniform impulse and Gaussiannoise: [Tk1 Tk2] =[255]
switching bilateral filter1
-Switching bilateral filter
  • Propose a new universal noise removalalgorithm: the switching bilateral filter (SBF)
    • Parameter selection:
      • For “edge” σS= 3, otherwise σS = 1.
      • σR= [30,50] will work well, we choose σR= 40.
conclusions
Conclusions
  • Propose SQMV for edge/texture detection, noise detection and switching bilateral filter.
  • The noise detector shows a good performance in identifying noise even in mixed noise models.
  • In most of the noise model cases, proposed filter outperforms both in PSNR and visually.
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