Binary Alpha is a very simple, yet super convenient expression that I use all the time, and decided to turn into a quick gizmo.
It analyzes a choice of the RGB, RGBA, or Alpha input and outputs an Alpha Channel (or RGBA result) that is Binary, 0 or 1. Any Pixels that are not 0 will be turned into 1 (negative numbers also), and 0 will remain 0.
This is perfect for those “blur, unpremult, set alpha, blur” for tricks extending colors, or if you need a quick matte for finding any rgb color above or below 0, in a CG render passes for example.
The good ol’ blur/unpremult/blur ❤ :
Basic properties:
The literal tcl expression is just:
r!=0 || g!=0 || b!=0 || a! = 0 ? 1 : 0
Which in english, translates to something like:
“if red is not 0, or green is not 0, or blue is not 0, or alpha is not 0, then be 1, or else, be 0”
So it will include negative pixels as an output as 1 as well.
Super simple but hopefully a time saver if you are like me and hate remembering expressions.
Find the tool on nukepedia here:
http://www.nukepedia.com/gizmos/channel/binaryalpha
You can also download this tool at my github, where you’ll find all my public tools in one place:
https://github.com/CreativeLyons/Lyons_Tools_Public/blob/master/04_Channel/BinaryAlpha.nk
Enjoy
Compositing Mentor 