A Method for Removing Salt and Pepper Noise from Image
A salt-and-pepper noise and image technology, applied in the field of denoising and restoration, can solve problems such as roughness and inability to completely describe the grayscale characteristics of the neighborhood, and achieve the effect of reducing adverse effects and improving effects.
Active Publication Date: 2016-02-17
FUJIAN HUICHUAN DIGITAL TECH
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[0008] (1) The local window itself does not contain edges. In this case, the so-called optimal direction is not the real edge direction. Only considering the adjacent pixels in this direction will make it impossible to fully describe the grayscale characteristics of the neighborhood.
[0009] (2) MDWMF uses the extreme gray value (0 and 255) conditions to remove the noise points of the neighbors. This method is rough, and the non-noise points with the extreme gray value may also be removed.
It can be seen that the best direction may not be the real edge direction, and there is a problem with MDWMF's approach
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[0035] The content of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments of the description:
[0036] A method for removing salt and pepper noise from an image, comprising the steps of:
[0037] A. Identify p i,j Whether it is a salt and pepper noise point. Its recognition method can be obtained from a given image with a pixel point p i,j As the center m×m local window Ω, using figure 1 The minimum value of the sum of the absolute gray difference between the central pixel and the adjacent pixels in the four directions shown in (a) and the extreme gray value are used for identification.
[0038] B. When p i,j When it is a non-salt and pepper noise point, keep its gray level unchanged, that is, r i,j =f i,j , where f i,j and r i,j Respectively represent the pixel point p i,j Grayscale before and after restoration by filtering.
[0039] C. When p i,j When it is a salt and pepper noise point, get the pix...
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The invention relates to a method for removing salt-pepper noises in images, which comprises the following steps: A, identifying whether pi, j is a salt-pepper noise point; B, when the pi, j is a salt-pepper noise point, acquiring a 3*3 local window omega 3 centering on the pixel pi, j, and estimating a noise density d (omega 3) of the omega 3; C, when the noise density d (omega 3) obtained in the step B is less than 9, defining a filter output ri, j of the pi, j as follows: omega (fs, t, fi, j) = exp (-beta |fs, t - fi, j |); and D, when the noise density d (omega 3) obtained in the step B is equal to 9, defining the filter output ri, j of the pi, j as the steps in the specification. The invention aims to provide a method for removing salt-pepper noises in images, through which salt-pepper noise points in an area adjacent to some pixel can be removed better, so that adverse effects on the filter output of center pixels caused by noise points in local windows us reduced, and a more accurate filter output is obtained by using a new direction weighted average strategy.
Description
technical field [0001] The invention belongs to the technical field of image processing, and relates to a method for denoising and restoring an image polluted by salt and pepper noise. Background technique [0002] Salt and pepper noise is a common noise that can be caused by a variety of factors, such as sensor hardware failures or communication channel interference. Salt and pepper noise is manifested as black (grayscale 0) or white (grayscale 255) pixels that are incompatible with neighboring pixels in the image. There is a sudden change in gray level between the noise point and the adjacent pixel point, resulting in a large gradient value, which makes it easy to be confused with the edge point, which brings great difficulties to image analysis, especially edge detection. [0003] Switching median filter is a recent research hotspot in the field of image salt and pepper denoising. The so-called switch means to detect the salt and pepper noise points in the image first, ...
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IPC IPC(8): G06T5/00
Inventor 李佐勇刘伟霞
Owner FUJIAN HUICHUAN DIGITAL TECH