Suppose we have an image of a wave: This wave is inverse transformed to one in the frequency coordinates. To do so, use short time fourier transform. Here we use method signal.stft from scipy: from scipy import signal
f0, t0, Zxx=signal.stft(original_wave, fs=1 ) where fs is the sampling frequency. Then plot it ax.plot(f0, Zxx, lw=2.5)