Nonlocal means denoising using a content-based searching region

The recent Nonlocal Means (NLM) filter shows excellent performance for image denoising. We investigate the effect of two key parameters on NLM: the searching region size and the decay parameter of the weights. We testify the general knowledge that the denoising performance can be improved by adjusting the searching region size and using an optimum decay parameter. Based on this observation, we adaptively choose the size of the searching region according to the edge contents of an area, and present a linear estimation for the decay parameter. Experimental results show that the proposed algorithm achieves much better denoising performance compared with the original NLM filter.