Magnitude spectrum

The magnitude spectrum tells you how strong are the harmonics in a image and the phase spectrum tells where this harmonic lies in space .

The magnitude tells you the strength of the frequency components relative to other components. The phase tells you how all the frequency components align in time . Plot the magnitude and the phase components of the frequency spectrum of the signal. The magnitude is conveniently plotted in a logarithmic scale (dB).

The FFT function computes the complex DFT and the hence the results in a sequence of complex numbers of form . The amplitude spectrum is obtained. For obtaining a double-sided plot, the ordered frequency axis (result of fftshift) is computed based on the sampling frequency and the amplitude spectrum is plotted.