Noise Power Estimation by Adaptively Thresholding Wavelet Packets

We present a novel method to estimate the noise power using the minimum statistics approach. The proposed method separates a noisy image into multiple frequency bands using the wavelet packet transform. By assuming that the output of the high-pass filter contains both signal detail and noise, the proposed algorithm extracts the region of pure noise from the high frequency band using an appropriate threshold. The region of pure noise, which is free from the signal detail part and the DC component, is well suited for minimum statistics condition, where the noise power can easily be extracted.