Rotating a layer against another leaves an unjustifiable white line

[NickPearl]

I need to reduce the inseam of somebody's shorts.
The technique that I have thought about that can do this is to rotate her legs. So, I rotate one leg and then I rotate another leg.
However, this process leaves an absolutely unjustifiable white line that cannot be fixed.

Here are the details:

The original picture is this:
https://i.imgur.com/XVLBbZ9.jpeg

I load it into GIMP by Ctrl+Shift+V.
Then I use the free-form select to select the area that I want to rotate.
Here is the selection:
https://i.imgur.com/U9t5siP.jpeg

Then:
Edit -> cut
Edit -> Paste as -> Paste as single layer in place
In the Layers window (bottom-right of the screen), I move the new layer below the main layer.
At this point, it looks like this:
https://i.imgur.com/cqcRJdA.jpeg

Then, In the Layers window (bottom-right of the screen), I select the main layer, and add alpha channel to it.
Then I select the fuzzy select tool. Then I click inside that white area.
Then I press the Delete button.

As a result of that, the leg becomes visible THROUGH the hole in the main layer.
It looks like this:
https://i.imgur.com/YketQ4c.jpeg

Then I rotate the Leg layer.
Here is the result:
https://i.imgur.com/DxZfbhu.jpeg

Then I merge all the layers.
Then I flatten the image.
Here is the final result:
https://i.imgur.com/SDNYibB.jpeg

As you can see, the two triangular white shapes are justifiable side effects of the rotation, and I can easily fix them.
However the white line is ABSOLUTELY NOT a justifiable side effect of the rotation, because the rotation rotates the back layer (the leg) towards and partially to the back of the main layer. So it shouldn't create an empty space (an empty line) between the two layers.

Also, please note that fixing that white line is not possible (or maybe not easy) because it is right next to the sewing line of the zipper. If I use the heal tool to remove the white line, the sewing line will also be removed, which is absolutely not acceptable.

1. Why does that white line happen?

   I really don't understand why this happens.
   Can you please shed some light on this issue?
   Please note that doing this same thing in other apps (for example Microsoft Paint) does NOT create that white line.

2. How can I avoid that white line?

3. If it is impossible to avoid it, how can I fix it?

Please help.
Thanks a lot for your help.
Nick P.

[rich2005]

You are using fuzzy select tool ? I think it is the wrong tool, free-select is better. Whichever one used, turn off any anti-aliasing option. I have seen transparent edge pixels become opaque when rotated. It is a bit of a bug that AFAIK never fixed.

You might want to try a different work-flow
Make your selection
Copy the selection, then close the selection.
Paste as a new layer
Rotate the layer.

A little video of that, I use Unified Transform but Rotate is ok . Only on leg https://sendvid.com/81bwqgvr 1 min 30 secs no audio.

[NickPearl]

(04-20-2026, 03:03 PM)rich2005 Wrote: You are using fuzzy select tool ? I think it is the wrong tool, free-select is better. Whichever one used, turn off any anti-aliasing option.  I have seen transparent edge pixels become opaque when rotated. It is a bit of a bug that AFAIK never fixed.

You might want to try a different work-flow
Make your selection
Copy the selection, then close the selection.
Paste as a new layer
Rotate the layer.

A little video of that, I use Unified Transform but Rotate is ok .  Only on leg https://sendvid.com/81bwqgvr  1 min 30 secs no audio.

Thanks for your help.
I took your advice and unchecked the anti-aliasing, and that white line went away.

Now, instead of a white line, there is a sharp line (the break between two sides):
https://i.imgur.com/aqiswqc.jpeg

The areas on the background (for example the area between the two legs) where that break line happens, are very easy to fix. Those areas can be fixed even as easily as using the heal tool (pressing H).
But areas on the shorts where that break line happens, are very difficult to fix, because on the shorts, there are the natural "waves" (or bunching) of the fabric (or whatever they are called) and smoothing out the break line such that those fabric waves (or bunching) straddle the break line smoothly is difficalt.

I even have the Resynthesizer add-on, and I try to use it (Filters -> Resynthesizer -> Heal section):
https://i.imgur.com/OP9qdyn.jpeg

This add-on tool removes the break line , but the result is not a very smooth transition of those fabric waves (or bunching) across the break line.
How can I remove that break line while creating a smooth transition of those fabric waves acoss the two sections?

Please help.
Thanks a lot for your help.
Nick P.

[rich2005]

Just keep experimenting.  Some obvious breaks between sections can be fixed with the clone tool or I tend to go for the smudge tool.  Resynthesizer,- heal selection, using from sides is correct but it is a smallish image, try 10 pix sampling and Inwards towards Center.  

Selections.  If you are will to spend a little time, then making a path outline (then selection from path) might give a cleaner result. You do need to keep an eye on overlaps.  Something like this.

   

Then I fear it becomes a bit of an artistic exercise, patching any defect - hand - arm - shirt folds...  I can get this.

   

I can't post on imgur, it is blocked in the UK   Keep looking in, someone might come up with a good procedure.