Border left around selection when selecting by color

[Chellrose]

Hi,

Using GIMP 2.10.34 on Debian 12.  When I "select by color" and then either cut the selection or fill it with a different color, it leaves behind a border of the old color.  This happens with the fuzzy select too.

The antialiasing option on select is off/unchecked.  I've tried it with and without antialiasing, no change in results.

This happens even with single-color images that I've made, so I know it isn't fuzziness from some JPEG or something like that.

Steps to reproduce with own image:

1. Make 2 layers, one a white background layer and the second either white or transparent.  (This is to give a full white background to see the border easily)
2. On the top layer, make an elliptical selection.
3. Using bucket fill, fill the selection with a single color.  (Anything but white)
4. Select None
5. Using Select By Color, select the area made in step 3.  (FWIW, I'm using Select By Composite with a threshold of 20.0)
6. Either cut the selection, or fill it with a different color.

A border of the old color is clearly visible (if you filled with color, you may need to zoom in a bit to see it.)  The border appears to be 1-2 pixels wide, with varying shades (or opacities, I'm not sure) of the old color.

Can anyone tell me how to fix this?  I'd like to be able to "select by color" the whole area, and cut or fill it without leaving a border.  My searches so far yield the suggestion to turn off antialiasing in the selection, but again, I do have antialiasing off.  I've attached screenshots showing the initial colored region and the border left behind.

Thank you!

[PixLab]

Increase the Threshold by sliding down your mouse while clicking on the canvas and it should work (it worked for me for this test, needed to slide down to 172 on the threshold)

Or ➤ Increase the feather edges,

   

Then just filling by drag n drop,

   

But if you want to delete with feather edges ➤ when you delete ➤ delete 2-3 times, hit the delete key few times (you can reduce the feather edges before deleting, though)

[rich2005]

@Chellrose
For this particular case, large-ish canvas, with coloured circle on white.

From your screen shot the threshold value = 15 which is the default value. You need to increase the value to include the anti-aliased edge pixels. In this case to a high value 250. (if maximum  256, all the image is selected)

   

It is more usual, just to grow the selection Select-> Grow a pixel or two, to include the edge pixels. All depends on what is selected.

[Ofnuts]

https://www.gimp-forum.net/Thread-Backgr...r-graphics