How to rotate selection

[depmco]

I've used Gimp for a while, but only in the most rudimentary way.  I'm now trying something new for me that has me stumped. I've RTFM, searched online and watched YouTube vids, but I must be obtuse.

I have a scan containing two fragments of a document that I want to piece together. I successfully moved the fragments apart and now want to rotate each piece individually. I selected one piece using Tools->Selection Tools->Rectangular Select. Next I activated Tools->Transform Tools->Rotate. In Tool Options, I set Transform: Selection. I'm up to this step in the first screenshot. I enter a rotation, 90 degrees. I get a crawling ants frame that is otherwise all white. When I select Rotate, the blank white crawling ant frame remains. The originally selected region remains unchanged (second screenshot).

I'm sure I'm missing something obvious, but how do I accomplish the rotation I want?

-- Greg

[Scallact]

(3 hours ago)depmco Wrote: I've used Gimp for a while, but only in the most rudimentary way.  I'm now trying something new for me that has me stumped. I've RTFM, searched online and watched YouTube vids, but I must be obtuse.

I have a scan containing two fragments of a document that I want to piece together. I successfully moved the fragments apart and now want to rotate each piece individually. I selected one piece using Tools->Selection Tools->Rectangular Select. Next I activated Tools->Transform Tools->Rotate. In Tool Options, I set Transform: Selection. I'm up to this step in the first screenshot. I enter a rotation, 90 degrees. I get a crawling ants frame that is otherwise all white. When I select Rotate, the blank white crawling ant frame remains. The originally selected region remains unchanged (second screenshot).

I'm sure I'm missing something obvious, but how do I accomplish the rotation I want?

-- Greg

The "selection" option rotates the selection mask itself, not the pixels inside.

Chose the "Layer" option instead. Since you have a selection active, this will create a floating layer with the selected pixels only (as you intended). Don't forget to anchor it down, or create a new layer with it.

[rich2005]

The obvious is a selection (boundary) has to contain some content, usually by copying but sometimes by cutting. What you use depends on the image.

For a scan like that, with a plain background.
First check that there is no transparency.  Layer -> Transparency -> Add Alpha should be greyed out

Then in pictures:
(1) Make the selection and cut it (ctrl-x)
(2) Paste that as a new layer

   

(3) Rotate (and move) as required.
(4) You can leave it in its own layer for future editing or merge back down into the base layer.

   

That is using a linux Gimp 2.10.38