General Failure

1) with a big pict it is slow 2) the only reference you have is when you position the dialog along the line. That is not very accurate. I just wanted to point to a simple, but very convenient functionality, which was not yet in paint.net. the method youu give is a kind of workaround. For my job i have a bunch of pics with photographic screenshots of a PLC screen (no direct printscreen possible) with photoshop the alignment is quick and correct. with paint.net its a lot of work

No, that's not what i want (I already knew that one) What i want is: click to points on a pic (which are not exactly horizontal) and the app should calculate the angle and make it horizontal. I dont have open webspace, otherwise i could show a pic which might explain.

When I have a scan or photograph which is not horizontal, i want to align it. Currently it's a trial and error itteration. In other photo editors there is an align function: you pick 2 points on a straigh element in the picture (and a grey help line is drawn between them) then you tell if this line has to be perfect horizontal or vertial. On OK the app determines the angle to rotate. Should not be too hard to add this very wanted functionality?