Wavelet Denoising

Wavelet denoising reduces high frequency noise.

A direct wavelet transform is computed from the original image.

Noise level at each wavelet scale is estimated separately.

This defines a threshold for zeroing wavelet coefficients.

Other wavelet coefficients are shrinked according to local variance estimation (Soft thresholding, Donoho, 1995).

After inverse wavelet transform, the image is renormalized.