How can I cut exactly the first harmonic (H1) from a FFT of an image

1. How do you find the harmonics of a Fourier series?
2. What are harmonics in FFT?

How do you find the harmonics of a Fourier series?

where an and bn are the coefficients of the Fourier series. They can be calculated by an=2T∫T0x(t)cos(2πntT)dtbn=2T∫T0x(t)sin(2πntT)dt.

What are harmonics in FFT?

Chapter 11: Fourier Transform Pairs. Harmonics. If a signal is periodic with frequency f, the only frequencies composing the signal are integer multiples of f, i.e., f, 2f, 3f, 4f, etc. These frequencies are called harmonics.