How to reduce the noise in images for ML

Hi,

I have an image data set which I would like to use for machine learning classification. My ML algorithm is correct and is working with the images of other data set. For a specific data set it's not working. It seems that the images I'm using have a lot of annoying salt-and-pepper noise, messing up my results. This noise is making my analysis less accurate and lower in quality.any advice or tips on how to tackle this salt-and-pepper noise issue using MATLAB? I'd appreciate some straightforward techniques or code examples if you have any.

[Rik]

Which strategies have you already tried? What was your top 3 Google results for 'matlab salt and pepper noise removal'?

Answer 1

[Hari]

Hi riksat,

I understand that you are experiencing issues with your machine learning classification due to salt-and-pepper noise present in a specific image dataset, and you are looking for ways to remove this noise to improve the accuracy and quality of your analysis.

I am assuming that you have access to Image Processing Toolbox. You can use the "medfilt2" function, which applies a median filter to the image. The median filter is particularly effective at removing salt-and-pepper noise without reducing the sharpness of the image.

Here's an example of how you can apply a median filter to an image with salt-and-pepper noise:

% Load the noisy image
noisyImage = imread('noisyImage.png');

% Apply a median filter to reduce salt-and-pepper noise
filteredImage = medfilt2(noisyImage, [3 3]);  % Using a 3x3 neighborhood

% Display the original and filtered images
figure;
subplot(1,2,1), imshow(noisyImage), title('Original Noisy Image');
subplot(1,2,2), imshow(filteredImage), title('Filtered Image');

In this code, "medfilt2" is used with a 3x3 neighborhood, which is common for salt-and-pepper noise removal. You can adjust the neighborhood size based on the level of noise in your images. I have tried this out by adding artifical salt and pepper noise in MATLAB. And It reduced the noise significantly.

Sample test results for the image I tested:

For information on the median filter and how to apply it, refer to the documentation of "medfilt2" https://www.mathworks.com/help/images/ref/medfilt2.html

To learn about reading and displaying images in MATLAB, you can look at the documentation of

"imread" - https://www.mathworks.com/help/matlab/ref/imread.html

"imshow" - https://www.mathworks.com/help/matlab/ref/imshow.html

Hope this helps!