negative value structural similarity index

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Jad Aoun
Jad Aoun on 21 Feb 2024
Commented: Matt J on 22 Feb 2024
Hello everyone ,
I aim to compare two 2D arrays which represent the reflectivity of an object.
I generate with the inbuilt ssim function the map of the structural similiraty index. And in some regions i get a negative value. I have read the description of the index and i do not get the physical meaning of a negative value.
P.S : my two images are positive double real numbers
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Jad Aoun
Jad Aoun on 21 Feb 2024
Thx for your answer Jonas but this does not help. I have two positive real matrixes which values are between 0 and 1 . And I have some local negative ssim values (not especially -1 ,-0.2 for instance) . I don't get the physical meaning . My images are not anti-correlated.

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Answers (1)

Matt J
Matt J on 21 Feb 2024
Edited: Matt J on 21 Feb 2024
A negative SSIM value means the values in those regions tend to be negatively correlated. When X goes low, then Y tends to go high.
  2 Comments
Matt J
Matt J on 22 Feb 2024
You're quite welcome, but if your question is resolved, please Accept-click the answer.

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