A structure adaptive window based non-local means(SAW-NLM)algorithm for image denoising is proposed to solve the problem that the results of the similarity measurement are not accurate in the non-local means(NLM)method. The proposed algorithm divides a noisy image into two parts
structural area and non-structural area
by using the primal sketch map that is extracted from the noisy image. Then
similar samples are respectively searched in these two parts using structure direction based adaptive window and isotropic window. Finally
the denoising result is estimated from these samples. Moreover
the window-wise method is employed in the estimation of the interest to suppress the pseudo texture phenomenon. Since the structure direction and the gray information are jointly used in the adaptive window
the similarity can be more accurately measured. Experimental results show that the SAW-NLM algorithm has advantages in the edge preservation and smooth effects. Comparisons with the traditional NLM algorithm show that SAW-NLM method improves the peak signal-to-noise by 1.1 dB and the structural similarity index by 4.6.
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