Bucket fill - fill whole selection also affects pixels outside of selection

[tidbit321]

I am posting thit to Gimp 2.8, because for some reason the option to post a thread is not available for me at the Gimp 2.10 section. (edit: moved for you)
My GIMP version is 2.10.6.x

Hello everyone,

first, I am happy to be (new) here and looking forward to meeting people who can help me with my GIMP questions. :-)

I have the following issue with the .png I added (logo_zachramnelesy_web.png). Most of the image is filled with various shades of green. I want all of these shades to become white (all the pixels the same color), and all the other pixels, transparent. The picture only has one layer.

I do the following:
1. Color select with a threshold of 50. I click on the background part of the image. Pixels get selected.
2. I click Delete - all the selected pixels have gone transparent (or so I believe).
3. Ctrl + I to invert selection. I want all the now selected pixels white and only white.
4. Bucket fill, with settings Mode = Normal, Opacity = 100, Fill type = FG color, Affected Area = Fill whole selection.
5. Click anywhere in the current selection. Most of the selection gets filled with clear white. But, some pixels on the edge only get gray. And, some pixels outside of the selection get gray as well. (after first bucket fill.png)
6. If I click again and again in the current selection, gradually all the pixels within the selection get clear white, but also some pixels outside of the selection are affected and get almost white. (after fifth bucket fill.png)

I don't understand how bucket fill with the setting "Fill whole selection" can affect some pixels within the selection differently than others within the selection, and affect pixels out of the selection.

I will be grateful for any help.

[rich2005]

With the procedure you are using you have lost most, but not all of the anti-aliasing. That is the semi-transparent pixels that give an impression of smooth edges. The bucket fill just fills those according to the transparency.

Without going into "why" you do not want anti-aliasing. You can remove the remnants with Layer -> Transparency -> Threshold Alpha The setting, almost but not quite maxed out. I put in a colored layer under just to make things a bit more obvious. Before is in the box.

[Espermaschine]

Just lock the alpha channel of the layer in the layers-tab and drag and drop white on it.

No need to select anything or use tools.