How can i normalize a greyscale image?

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Gn Gnk 2020-11-20

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评论： Saud Alfalasi 2020-11-21

Hello ,

I've seen many similar questions but i am still confused . I have a grayscale image and i want to normalize it.How can i do that ? I have seen that grey2mat() does the job but i am not sure .

Thank you.

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Answer 1

Image Analyst 2020-11-20

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What's your definition of normalize? You can use mat2gray(), rescale(), or simply divide by the actual max and multiply by the desired max. It just depends on how you define it. What's your definition? How do you plan on using it?

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Image Analyst 2020-11-21

编辑：Image Analyst 2020-11-21

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The second step is not necessary. Not sure why they wanted you to do it. Otsu's method can work with the original range. Rescaling the image does nothing to help it. It just finds the threshold at a different (higher) threshold than it would have with the original, unscaled image. But anyway, you can scale it like this:

imshow(topHatImage, []);
normalizedImage = mat2gray(topHatImage); % Rescale to 0-1 range.
imshow(normalizedImage, []); % Will look the same since I used [].
threshold = graythresh(normalizedImage)
mask = imbinarize(normalizedImage, threshold); % Apply Otsu method.
imshow(mask); % Display thresholded image.