ErodeSmooth node


This documentation is for version 2.0 of ErodeSmooth.


Erode or dilate input stream using a normalized power-weighted filter.

This gives a smoother result than the Erode or Dilate node.

See “Robust local max-min filters by normalized power-weighted filtering” by L.J. van Vliet,

Uses the ‘vanvliet’ and ‘deriche’ functions 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


Input Description Optional
Source   No
Mask   Yes


Parameter / script name Type Default Function
Range / range Double min: 0 max: 1 Expected range for input values.
Size / size Double x: 0 y: 0 Size (diameter) of the filter kernel, in pixel units (>=0). The standard deviation of the corresponding Gaussian is size/2.4. No filter is applied if size < 1.2. Negative values correspond to dilation, positive valies to erosion. Both values should have the same sign.
Uniform / uniform Boolean Off Apply the same amount of blur on X and Y.
Exponent / exponent Integer 5 Exponent of the normalized power-weighted filter. Lower values give a smoother result. Default is 5.
Border Conditions / boundary Choice Nearest
Specifies how pixel values are computed out of the image domain. This mostly affects values at the boundary of the image. If the image represents intensities, Nearest (Neumann) conditions should be used. If the image represents gradients or derivatives, Black (Dirichlet) boundary conditions should be used.
Black: Dirichlet boundary condition: pixel values out of the image domain are zero.
Nearest: Neumann boundary condition: pixel values out of the image domain are those of the closest pixel location in the image domain.
Filter / filter Choice Quadratic
Bluring filter. The quasi-Gaussian filter should be appropriate in most cases. The Gaussian filter is more isotropic (its impulse response has rotational symmetry), but slower.
Quasi-Gaussian: Quasi-Gaussian filter (0-order recursive Deriche filter, faster).
Gaussian: Gaussian filter (Van Vliet recursive Gaussian filter, more isotropic, slower).
Box: Box filter - FIR (finite support / impulsional response).
Triangle: Triangle/tent filter - FIR (finite support / impulsional response).
Quadratic: Quadratic filter - FIR (finite support / impulsional response).
Expand RoD / expandRoD Boolean On Expand the source region of definition by 1.5*size (3.6*sigma).
(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.