FFT2 of an image

I have an intenisty information of an image. I have performed an FFT2 of that image. FFT2 gives the lower and higher frequencies in the frequency domain of that image. Now the result I got is the amplitude or intensity of those frequencies?

Answer 1

[Ameer Hamza]

You can use abs(): https://www.mathworks.com/help/matlab/ref/abs.html on the output of fft2() to get the intensity values.

[Rakesh V]

Hi Ameer hamza,

The abs of output of the fft2 gives the magnitude of the output, but not amplitude.

You mean the mangitude is the amplitude.

if I takes abs(output)^2 gives me the intensity

[Ameer Hamza]

Yes, you are correct. The abs() of fft2() gives the magnitude. You then need to divide by the number of samples in original signals to get the amplitude. And the square of amplitude will be intensity.

[Rakesh V]

Hi Ameer Hamza,

How exactly do I convert the magnitude spectrum to amplitude for an image.

what is the number of samples for a given image.

I need to convert the power spectrum to amplitude.