Converts a black and white 'scan' -- or other linework without transparency, to a layer with transparency corresponding to white in original image and black to solidity, with intermediate brightnesses translating to intermediate levels of solidity of black.
In short -- converts white -> transparency, black -> solid, with full antialiasing. This is a one-step process, no choosing of parameters is needed.
Also locks the alpha of the lineart layer so that it's easy to color the lines.
You are then expected to do your coloring on layers beneath.
This is a more flexible lineart coloring system, as opposed to setting the lineart layer to multiply mode and coloring on the layers beneath -- that method prevents you from adding color to your lineart.
This method makes it easy to do so.
Written on behalf of everyone who has ever done a crappy coloring by painting on top of the original lineart layer and leaving smudges of uncolored gray and white, and even those who are doing so presently.
This script should make coloring a lot easier for you!