# SmoothPatchBased node¶

This documentation is for version 2.0 of SmoothPatchBased (net.sf.cimg.CImgDenoise).

## Description¶

Denoise selected images by non-local patch averaging.

This uses the method described in: Non-Local Image Smoothing by Applying Anisotropic Diffusion PDE’s in the Space of Patches (D. Tschumperlé, L. Brun), ICIP’09 (https://tschumperle.users.greyc.fr/publications/tschumperle_icip09.pdf).

Uses the ‘blur_patch’ function from the CImg library.

CImg is a free, open-source library distributed under the CeCILL-C (close to the GNU LGPL) or CeCILL (compatible with the GNU GPL) licenses. It can be used in commercial applications (see http://cimg.eu).

## Inputs¶

Input Description Optional
Source   No
Spatial Std Dev / sigma_s Double 10 Standard deviation of the spatial kernel, in pixel units (>=0).
Value Std Dev / sigma_r Double 0.05 Standard deviation of the range kernel, in intensity units (>=0). In the context of denoising, Liu et al. (“Noise estimation from a single image”, CVPR2006) recommend a value of 1.95*sigma_n, where sigma_n is the local image noise.
Patch Size / psize Integer 5 Size of the patchs, in pixels (>=0).
Lookup Size / lsize Integer 6 Size of the window to search similar patchs, in pixels (>=0).
Smoothness / smoothness Double 1 Smoothness for the patch comparison, in pixels (>=0).
fast Approximation / is_fast_approximation Boolean On Tells if a fast approximation of the gaussian function is used or not
(Un)premult / premult Boolean Off Divide the image by the alpha channel before processing, and re-multiply it afterwards. Use if the input images are premultiplied.
Invert Mask / maskInvert Boolean Off When checked, the effect is fully applied where the mask is 0.
Mix / mix Double 1 Mix factor between the original and the transformed image.