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mei_mei

FFT and frequency domain

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Hello everyone, I have implemented a FFT, I have high, low, band pass filters, and I have to implement a filter, which will denoise the picture (if it has some noise, for example like horizontal, vertical or diagonal stripes or spots). I have tried to use a threshold and "erase" wrong artifacts but it doesn't work quite good :(. Do you some ideas? Thnx a lot.

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You get "ringing" artifacts, right? This happens whenever you aggressively threshold in the frequency domain. If you make the transition smoother (not just a sharp cutoff) you'll get better results.

If you have a good noise model, then there is a least-squares-optimal filter called the Wiener filter that you can use.

One issue, though, is that mean-squared-error isn't actually a very good metric for how good something looks. So often more heuristic things (like median filters) end up looking better (these are good for "salt and pepper" type noise).

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