Channel Key Node

../../../_images/compositing_node-types_CompositorNodeChannelMatte.png

Channel Key Node.

The Channel Key node determines background objects from foreground objects by the difference in the selected channel’s levels.

For example in YUV color space, this is useful when compositing stock footage of explosions (very bright) which are normally shot against a solid, dark background.

Inputs

Image
Standard image input.

Properties

Color Space

This button selects what color space the channels will represent.

RGB, HSV, YUV, YCbCr

Channel
This button selects the channel, defined by the Color Space, to use to determine the matte.
Algorithm
Max., Single
Limit

It is possible to have a separation between the two values to allow for a gradient of transparency between foreground and background objects.

High
Determines the lowest values that are considered foreground. (Which is supposed to be – relatively – height values: from this value to 1.0.)
Low
Determines the highest values that are considered to be background objects. (Which is supposed to be – relatively – low values: from 0.0 to this value.)

Outputs

Image
Image with an alpha channel adjusted for the keyed selection.
Matte
A black-and-white alpha mask of the key.