FFT transform:
FFT function is an effective tool for computing the discrete Fourier transform of a signal.In fourier
transform it actually change the domain of the image. In this we get the restored image after taking the inverse
FFT. The FFT contains information between 0 and fs, however, we know that the sampling frequencymust be at
least twice the highest frequency component. Therefore, the signal's spectrum should be entirly below fs/2 , the
Nyquist frequency