MATLAB: How to remove noise without effecting the image

denoisingimage enhancementImage Processing Toolboxnoise

hi,

I have been trying to do image enhancement, but I found the noise is there any way to remove such kind of noise and what to call this kind of Noise given in following image

I tried median filter but it blur this image, kind of lost some details in image by adding blurring effect. Thanks for your Suggestions

Best Answer

What kind of noise is it? All noise removal methods will affect the image - they have to otherwise the image won't change and get noise removed. Why do you need that noise removed? It doesn't look that bad - bad enough to prevent you from doing whatever else you need to do with the image.

There are many types of noise removal and many are best suited for a particular kind of noise. If you have isolated salt and pepper noise, I have a modified median filter that does a great job on that. There are other denoising methods with different properties and effect. It seems BM3D is the current state of the art that people are trying to beat. There are others that are almost as good and perhaps even better for certain types of images. They range from the simple mean and median to slightly more complicated sigma filters and knn filters to more sophisticated and complicated mean shift, non-local means, BM3D, K-LLD, UINTA, K-SVD, plus more being invented every month. Look up some of those. I know there are some non-local means programs in the File Exchange. Maybe you can start with those.

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MATLAB: Noise removal from the part of the medical image where noise is actually present, not the whole image

If you know what regions of the images you have noise that needs filtering why not just filter those regions? Something like this (one-region example):

regN = [i11,i12,i21,i22]; % corners of noisy region
ImgN = Im_full((regN(1)-1):(regN(2)+1),(regN(3)-1):(regN(4)+1)); Will break down for regions that extends to image edges, fix to suit needs
ImgN = wiener2(ImgN,[3,3]); % Or whatever filtering suits your images
Im_full(regN(1):regN(2),regN(3):regN(4)) = ImgN(2:end-1,2:end-1);

To me it sounds strange that you need to reduce noise in what seems to be "medically uninteresting" parts of images, while the parts of the images with organs and tissue should be left unfiltered with noise intact. Why not simply tell the doctors that the noisy parts of the images are left noisy to make them aware of the general noise characteristics of the images, that should be information that should help image interpretation.

HTH

MATLAB: What is the reason for adding noise in image by adding variance

You need to give more context than that. Increasing the variance does not necessarily add noise. For example, merely stretching the contrast will increase the variance. Of course if you add something not originally in the scene, there is a possibility that doing that will increase the variance, though adding a negative image will, or could, decrease variance.

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MATLAB: Noise removal from the part of the medical image where noise is actually present, not the whole image

MATLAB: What is the reason for adding noise in image by adding variance

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