ChromaBlur node — Natron 2.5.0 documentation

# ChromaBlur node

This documentation is for version 4.0 of ChromaBlur (net.sf.cimg.CImgChromaBlur).

## Description

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 http://cimg.eu).

## Inputs

Input | Description | Optional
--- | --- | ---
Source |  | No
Mask |  | Yes

## Controls

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 blur is applied if size < 0.24 (Gaussian and quasi-Gaussian) or <= 1 (box, triangle and quadratic).
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.