FFT with ImageMagick

Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
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claus_01
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Joined: 2019-03-03T19:52:44-07:00
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Location: Ludwigsburg

FFT with ImageMagick

Post by claus_01 »

Hello,

I have an image I want to denoise using the FFT feature of ImageMagick.

The image:

Image

This is btw taken from a film by German director, Rainer Erler ('Die Delegation'). The 'aliens' are actors with a special make-up. Mr. Erler kindly gave me permission to use this still, which is unfortunately very noisy.

After applying

Code: Select all

convert image.jpg -fft  \( +clone  -write image_phase.png +delete \) +delete -write image_magnitude.png  -colorspace gray -auto-level -evaluate log 100000  image_spectrum.png
I got this spectrum

Image

but what areas do I mask out? There are no dots as in the example on the ImageMagick page.

TIA,

Claus
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fmw42
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Location: Sunnyvale, California, USA

Re: FFT with ImageMagick

Post by fmw42 »

That FFT denoising technique will only remove noise that has a regular pattern. Your image does not qualify for the approach and is way to randomly grainy. You will have to use typical spatial domain median filtering or averaging. Or you can try -despeckle or -enhance or -kuwahara or -cmeans processing.
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