Fast Fourier Transform of an arbitrary wave


The user can draw an arbitrary time domain signal on the graphics surface
using mouse. On every change in the time domain signal, the program will draw
its FFT & the reconstructed signal with certain cutoff frequency. The
cutoff is determined by a number in a spin box on the control panel on the left
side of the graphics surface. The range is 0 to 315. The cutoff frequency is
the value in the spin box divided by 100. For example, if the value in the spin
box is 50, the cutoff will be at 50/100 radians. The cutoff will be clamped at
frequency of PI radians. At Pi radians cutoff, all the frequencies will be
considered for reconstruction of the time domain signal.
Download the Program
In the following screenshots 
 White colored signal  User drawn time domain signal
 Yellow colored signal  FFT of the time domain signal
 Blue colored signal  Reconstructed time domain signal after including all the frequencies below the cutoff