Python equivalent of MATLAB otf2psf

Question

Is there a library that does in Python what MATLAB's otf2psf function does?

Here is the documentation of the MATLAB function. I understand that this is done by a Fast Fourier Transform. I did find something that does psf2otf in here. But I could not find something that does it the other way around.

Answer 1

In Python, there's no direct equivalent of MATLAB's otf2psf function. You can achieve the same effect using the inverse Fourier transform (ifftn) and some additional processing.

Here's a basic implementation in Python:

import numpy as np
from numpy.fft import ifftn, fftshift

def otf2psf(otf, shape=None):
    if shape is None:
        shape = otf.shape
    
    # Inverse Fourier transform
    psf = ifftn(otf, shape)
    
    # Shift the zero-frequency component to the center
    psf = fftshift(psf)
    
    # Take the real part, as the PSF should be real-valued
    psf = np.real(psf)
    
    # Normalize the PSF so that its sum is 1
    psf /= np.sum(psf)
    
    return psf

You can use this function to convert an OTF to a PSF in Python. The shape parameter allows you to specify the desired shape of the PSF.