ChromaBlur node


This documentation is for version 4.0 of ChromaBlur.


Blur the chrominance of an input stream. Smoothing is done on the x and y components in the CIE xyY color space. Used to prep strongly compressed and chroma subsampled footage for keying.

The blur filter can be a quasi-Gaussian, a Gaussian, a box, a triangle or a quadratic filter.

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
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.
Uniform / uniform Boolean Off Apply the same amount of blur on X and Y.
Colorspace / colorspace Choice Rec. 709
Formula used to compute chrominance from RGB values.
Rec. 709 (rec709): Use Rec. 709 with D65 illuminant.
Rec. 2020 (rec2020): Use Rec. 2020 with D65 illuminant.
ACES AP0 (acesap0): Use ACES AP0 with ACES (approx. D60) illuminant.
ACES AP1 (acesap1): Use ACES AP1 with ACES (approx. D60) illuminant.
Filter / filter Choice Gaussian
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 (quasigaussian): Quasi-Gaussian filter (0-order recursive Deriche filter, faster) - IIR (infinite support / impulsional response).
Gaussian (gaussian): Gaussian filter (Van Vliet recursive Gaussian filter, more isotropic, slower) - IIR (infinite support / impulsional response).
Box (box): Box filter - FIR (finite support / impulsional response).
Triangle (triangle): Triangle/tent filter - FIR (finite support / impulsional response).
Quadratic (quadratic): Quadratic filter - FIR (finite support / impulsional response).
(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.