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Comment by spockz | Hacker News Reader

Awesome read! Is this in use by any software already? I can imagine someone at Adobe already implementing this in photoshop. Can we apply this quickly enough to let everyone where whatever stripes they want on television?

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With GIMP:

https://www.youtube.com/watch?v=30XaCfM2QGg

https://www.youtube.com/watch?v=se9I3uGITR0

With Photoshop:

https://www.youtube.com/watch?v=vb4XFNC4MvU

I am sure there are more tools for it. Good search terms seem to be "FFT Moire".

Fourier transforms can be easily computed in realtime at full HD resolution these days since GPUs are very fast at that kind of math.

This is not a general-moire-removal technique. It's basically a band-stop filter that removes those frequencies from an image that correspond to the size of halftone dots both horizontally and vertically. Nifty use case for FFT though, would probably make a good homework assignment on an undergrad DSP course.

> removes those frequencies from an image that correspond to the size of halftone dots both horizontally and vertically

And all the harmonics that make out the circle shape.

I'm pretty sure that making the circle repeat horizontally and vertically is some kind of convolution product and that has some nifty properties under Fourier transform.

Someone has made this http://turbomaze.github.io/JS-Fourier-Image-Analysis/. I am sure a web version where you can manipulate the FFT and see the image reconstruction live should already exist somewhere.

EDIT: This fork allows drawing over FFT https://geeklogan.github.io/JS-Fourier-Image-Analysis/

If you mean DFT, then yes. It's basis for image/video compression, for example. ;)

That would be DCT - Discrete Cosine Transform.

Things you can do to a single image that look good do not directly scale to the same results to video, especially something in motion.

Also, this would be a good example of just because you can doesn't mean you should, especially with stripes.

It's implemented in affinity photo. You get realtime feedback- it's pretty amazing.

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