What parameters can a fourier transformation have? / How to process the shifted result?
<p>I have a simple Python 3 TKinter Image Editor using OpenCV3 and numpy.
I wanted to implement a Fourier Transform and used the first example from <a href="http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_imgproc/py_transforms/py_fourier_transform/py_fourier_transform.html" rel="nofollow">here</a> with numpy:</p>

<pre><code>f = np.fft.fft2(img)
fshift = np.fft.fftshift(f)
magnitude_spectrum = 20*np.log(np.abs(fshift))
</code></pre>

<p>I can't just use <code>fshift</code> as result and display it. Unfortunately the line with <code>20*np.log...</code> isn't explained on the site and reading other explanations for the fourier transform didn't explain it to me either.</p>

<p>Until now i have no parameter for this manipulation, but I tested that the output differs if I change 20 to something else. Should this be user configurable or why does this code example do this?</p>