User blog comment:CitizenA/Paint.NET silhouette plugin/@comment-7523816-20130403003306/@comment-5906821-20130403012728

I have never used GIMP, so I don't know if there any plugins that can do this on it. Now a quick search seems to reveal that making GIMP plugins aren't too much of a hassle, so perhaps I could perhaps try my hand at making one, but I really can't make any promises. It probably wouldn't be any time soon either.

With that being said, Paint.net is free and lightweight, so if you really want to use this plugin, downloading it is the simplest option.

I had also looked into making a photoshop version of it, but programming plugins for it is way too much of a hassle, as apparently their official development kit is invite-only and the alternatives are less than stellar to put it lightly.