How to "subtract" out bkgnd color, leaving transparency?

[IceUck]

Howdy folks,

I've been using paint.net for years, and it's my go-to tool for everything except the most heavy-duty photo touch-up.

There's one thing that I keep coming across, and I don't know how to do it. I'm wondering if this is possible with some combination of layer blending, or ... ?

So let's say you have this nice piece of artwork containing a figure against a single-color background (e.g. Mickey Mouse against a white background). If the artwork is high quality, Mickey's edges will blend into the white for a few pixels (otherwise, the original image would generally look aliased).

OK, so it's easy enough to use the magic wand to select the background. By adjusting the tolerance, you can get more or less of the "blended" pixels between Mickey's edges and the background. If you go to one extreme, you remove only the pure white background, leaving a white halo around Mickey. The other extreme removes all of the blended pixels around Mickey, resulting in an aliased look.

Now, if you were going to place the extracted Mickey on another white background, the halo isn't a problem. But if you want to place him on top of some other color, it looks bad.

I frequently run into this problem when I want to extract some artwork and make an icon out of it. What I'd like is to "subtract" the background color, leaving the edge pixels with their original color and some amount of transparency. Does anyone know how to do this?

Thanks in advance.

[BoltBait]

You're looking for my Feather plugin. Use the True Feather mode after you've done the magic wand/delete.