Category: 
Image Processing 
Author: 

Description: 
Some example functions/code which show how to do FFT manipulation. Please use/develop/expand and correct these examples at will.
To use this script, have an image with periodic information in it foremost. Something like a HRTEM image will do fine. The image must be square and have dimensions an integral power of 2 eg 512 x 512, 1024 x 1024 etc.
The script shows how to :
Calculate the FFT of an image
Calculate the inverse FFT of an FFT
Create a Butterworth filter to use for high frequency (noise) filtering
Apply the Butterworth filter to a FFT
Carry out the inverse FFT of the above to show the effect of filtering
Extract the real component of a complex image
Extract the imaginary component of a complex image
Compute the magnitude component of the FFT
Compute the Phase component of the FFT  don't stare at it too long
Compute the Power Spectrum of an image. 
Comments: 
Require real or integer images of appropriate dimensions.
Note (by B.Schaffer): You can use the transform.dll commands by C.Koch for a FFTW FourieTransform without these limitations.
You can additionally check the packedFFT examples by V.Hou.
There is also an example on how to create and apply masks on FFT for fourierspace filte 
Acknowledgements: 
Thanks to Bernhard Schafer and Kazuo Ishizuka for advice and assistance 
Script version: 
1.0 
DM/GMS version: 
3.11 
Script written as a function: 
No 
Source: 
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