Image noise filtering

Question

Hi,

I am looking for inputs on an image noise filter method. A 9-pixel median filter does not work very well with dense noise. Noise is periodic (periods of 50 lines) and additive.

Thanks, Bi

Answer 1

I like to use selective blurs, which finds the average of only the surrounding pixels whos values are within a certain range from the value of the center pixel.

Gimp has a weighted version of this called "selective gaussian blur" you could try to see what this looks like.

Answer 2

What about filtering in the Fourier domain? If the noise is periodic then with any luck your noise will appear as a pair of nice pointy features in Fourier space, where you can filter them with a couple of Gaussians then transform back to real space and your periodic noise should be gone.