Find image rotation angle using DFT

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Hi, I was using this tutorial :

https://docs.opencv.org/3.4/d8/d01/tu...

My aim is to use the dft result to rotate my original images so they are better aligned horizontally.

While getting the dft was a piece of cake I'm stuck however on the last part 'From this we may calculate the offset and perform an image rotation to correct eventual miss alignments.'

Can someone point me to some articles describing how you do calculate the offset? Preferably in python as the rest of my code is also in python.