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SAR image nonlocal mean value speckle filtering method

A non-local mean, image technology, applied in the field of image processing, can solve problems such as the generation of Gibbs phenomenon, achieve the effect of preserving and restoring edge and texture details, simple implementation process, and smoothing speckle noise

Inactive Publication Date: 2010-06-09
XIDIAN UNIV
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Problems solved by technology

However, the frequency domain speckle removal method is still essentially a filter based on a fixed window, and image structure information such as edges and lines will produce Gibbs phenomena.

Method used

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  • SAR image nonlocal mean value speckle filtering method
  • SAR image nonlocal mean value speckle filtering method
  • SAR image nonlocal mean value speckle filtering method

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Embodiment Construction

[0027] Refer to attached figure 1 , the present invention provides the realization method of SAR image filter, comprises the steps:

[0028] Step 1: Perform point target detection on a pixel of the input SAR image.

[0029] 1.1) Using the classic constant false alarm point target detection method, consider the pixels that meet the following conditions as point targets:

[0030] a: take the pixel as the center to take a fixed-size window, and the gray value of the pixel is greater than or equal to the gray value of the rest of the pixels in the window;

[0031] b: Take a window in the image, such as figure 2 As shown in (a), the average gray value of the 4-neighborhood window of the center pixel in the window is denoted as u 1 , the mean value of the gray value of the remaining pixels in the window 4-neighborhood window is denoted as u 2 , It should be less than the set threshold T, and T is 0.6 in the experiment;

[0032] 1.2) If it is a point target, keep the gray lev...

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Abstract

The invention discloses an SAR image nonlocal mean value speckle filtering method which belongs to the technical field of image processing, and mainly overcomes the problem of inaccurate distance computation of traditional SAR image nonlocal mean value speckle filtering similar blocks. The method comprises the following realization processes: 1. firstly judging whether a pixel point of an input SAR image is a point target, if so, keeping the gray value of the point target, otherwise performing the next step; 2. computing the distance between the pixel point and all pixel points in a search field according to a new distance measurement; 3. computing the weight values of all the pixel points in the search field according to the computed distance of all the pixel points in the search field; 4. carrying out weighted averaging for all the pixel points in the search field according to the computed weight values of all the pixel points in the search field to obtain the modified gray value of the pixel point; and 5. replacing the gray value of all points in the original SAR image with the modified gray value to obtain the speckle filtered SAR image. Compared with some traditional and classical speckle filtering methods, the invention can better smooth speckle noise and simultaneously keep the edge and texture details of the SAR image.

Description

technical field [0001] The invention belongs to the technical field of image processing, in particular to a speckle removal method, which can be used for speckle removal processing of SAR images. Background technique [0002] In recent decades, SAR images have been widely used in military and civilian applications. However, the imaging mechanism of SAR is different from optical imaging. Its special coherent imaging mechanism causes speckle noise in the image, so that the radar image of the target with uniform scattering coefficient does not have uniform grayscale and many spots appear, and the signal-to-noise ratio of the image decreases. It creates difficulties for target recognition and feature extraction, so smoothing noise and suppressing noise preprocessing is an indispensable process. The study of SAR coherent speckle suppression technology has always been a deterministic interference phenomenon inherent in SAR images, which is caused by the coherent effect of echoes ...

Claims

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Application Information

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IPC IPC(8): G06T5/00
Inventor 钟桦焦李成徐晶晶王灿王爽侯彪王桂婷马文萍尚荣华
Owner XIDIAN UNIV
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