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2 votes
Accepted

When computing the phash value for an image, why compare against the median?

It has to do with the number of ones and zeros that the median induces. By definition it will create a binary sequence of 32 ones and 32 zeros in most cases. So now similarity is well defined and ...
Mark's user avatar
  • 357
1 vote
Accepted

Why is the first DCT square black here for the DCT basis images?

For displaying purposes it is best to normalize your images to be between $0$ and $1$. Add the following line of code before plotting to normalize: ...
Ahsan Yousaf's user avatar
  • 1,533
1 vote

How to use DCT to compare images?

"Comparing two images" is a bit too vague. What do you compare for? Two identical photographs, say of the identical scene containing a cat, exposed differently, will have shifted histograms, ...
Marcus Müller's user avatar
1 vote

Sharpness in DCT domain image

There is no recipe for such thing. Moreover, image sharpness is not something well defined. For instance, homogenous image, is it sharp? Yet, for what we call real world images we usually have a ...
Royi's user avatar
  • 19.7k

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