2D FFT of Image and Sharpness I'm trying to make some simply autofocus algorithm for my device and pretty confused with 2D FFT results.
As I know for now - number of high-frequency's components in 2D FFT will say me that image is more focused, than other one where 2D FFT got more low-frequency's components. And i do not know how to calculate this parameter.

I'm thinking about applying high-pass filter, but how i should choose cut-off frequency? In 1D FFT it's pretty simple to determine just looking at the picture of 1D FFT..
What about just integrating the energy in the high frequencies?
You can do that after applying High Pass filter which is equivalent of weighting high frequencies differently.