How to actually invert the fuzzy selection?

[Ofnuts]

(10-28-2020, 01:22 PM)andreim Wrote: Intuitively when I invert selection I expect to select 1-alpha of the already selected pixels, plus  the -- until then -- unselected pixels.

This is how it works...

In the image below:

• Selection (ants, to the 50% selection line) is the purple dashed circle
  
• Leftmost is bucket-fill on selection
  
• Center is bucket-fill on inverted selection
  
• Rightmost is difference between the two, they are equal (black circle) on the 50% selection line