Compositing node

Premultiply

Converts between premultiplied alpha (colour already scaled by its own alpha) and straight alpha. Only reach for it when edges look wrong: a dark fringe on a composite usually means straight alpha needs premultiplying, and a bright halo means the reverse.

Download the patch Read it in the Field Guide

The Premultiply node in Infinite, showing its inputs, controls and outputs.

What it does

Premultiply is a compositing node: it layers, masks and routes pictures. It takes picture in and gives picture out.

Try it

If a keyed subject has a dark outline over a bright background, add this before the Blend.

Chroma Key Premultiply Blend

Inputs and outputs

Inputs

picture input

Outputs

picture out

Example patch

This patch wires Premultiply to what it needs and shows the result. Download it, then use File, Open in Infinite, or read it here: it is plain text.

infinite-patch 1
rev 2
# Premultiply: a starting patch for the Premultiply node
node 1 Compositing premultiply
  id node
  pos 520 300
end
node 2 Source Ramp
  id in0
  pos 0 300
end
node 3 Utility Output
  id out
  pos 1080 300
end
cable node 0 in0
cable out 0 node