Premultiply

Multiplies selected channels by a specified alpha channel.

user

Container for user-defined plugs. Nodes should never make their own plugs here, so users are free to do as they wish.

out

The output image generated by this node.

enabled

Turns the node on and off.

channels

The names of the channels to operate on. Names should be separated by spaces and can use Gaffer’s standard wildcards.

alphaChannel

The channel to use as the alpha channel. The selected channel does not have to be ‘A’, but whichever channel is chosen will act as the alpha for the sake of this node. This channel will never be multiplied by itself - it will remain the same as the input.

ignoreMissingAlpha

If set, this node will do nothing if the specified alphaChannel is not found, instead of throwing an error.

useDeepVisibility

When processing a deep image, you may use this to multiply by the visibility of the current sample, taking into account the alpha of all previous samples. This is a pretty special case, it’s mostly useful for converting deep images to incandescence, by multiplying RGB by visibility, and then wiping out the ‘A’ channel.