Compute either the log10 power or the amplitude spectrum. Note1, I am normalizing the FFT output by dividing by n_rows x n_columns. Note2, before FFTing the grid is cosine tapered to the extended dimension that better suits the two conditions: 1, the extended grid is at least 20% larger in both dimensions; 2, only “good FFT numbers” (with prime factors <= 5) are retained. Note3, this option is also available for rectangular ROIs.
Compute the grid autocorrelation (it uses FFT). Note that this option is also available for rectangular ROIs.
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