NEW IN R20
The Mask Node can be used to define the opacity of the Foreground color compared with the Background color and select the color portions to be taken into consideration.
Defines the opacity of the Foreground color and how large its portion is, which should then be blended with the Background color.
Only the portions of the input color activated here will be taken into consideration by the Node. The Alpha option expands the Node’s function to include the use of Alpha channels.