I am following http://homepages.inf.ed.ac.uk/rbf/HIPR2/fourier.htm . I understand the application of Fourier Transform behind Image Processing, but right now, I am curious about the mathematics behind it, and it is giving me a bit of a hard time.
For example:
In this formula, where do all these equations come from? Could somebody please elaborate the mathematics behind the scene in layman's term?