For anyone else wondering what an Opacity Swizzler does, it seems to fully remove the color black from images, and it de-saturates all other colors if present.
e.g.
Black + white image => transparent + white image.
Colored image => greyscale image, blacks replaced with transparency.
Neat tool, I can see it being useful for gamedev related things like image masks.
Runs on linux (arch btw) using wine 9-20.