Created attachment 122723 [details] attachment picture SUMMARY Both 4.2.6, latest nightlies. STEPS TO REPRODUCE 1. Select any area with any(Rectangular, Elliptical, Poligonal, Outline, etc) selection tool and paint on it(So that it becomes possible to transform). 2. Rotate, apply. OBSERVED RESULT Rough edges appear. EXPECTED RESULT Clean edges. SOFTWARE/OS VERSIONS Windows: Win7 macOS: Linux/KDE Plasma: (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
When did this start? Can you give a better example than a rectangle shape? There is always going to be some jaggies when you rotate something like that. This is just how computers work (unless you are talking about something I don't understand). People usually just get around this by either 1. Increase the DPI so it minimizes the jaggies 2. Work with vector files so the edges are calculated mathematically If I am not understanding, please explain it differently
Created attachment 122725 [details] attachment picture 2 Left : 4.1.5 Right : git b6d75fa Not this amount. Something definitely has changed along the updates. But I'm not sure exactly when. I'm not the dev. :/
Changing dpi doesn't make a difference.
Thanks for your comment! Automatically switching the status of this bug to REPORTED so that the KDE team knows that the bug is ready to get confirmed. In the future you may also do this yourself when providing needed information.
Which transformation filter(nearest neighbour, bicubic) are you using?
(In reply to wolthera from comment #5) > Which transformation filter(nearest neighbour, bicubic) are you using? Ok. Turns out it only happens with the Lanczos3 filter. So is it supposed to be in this way? (It seems to be the cleanest filter.)
The Lanczos3 filter is known to produce 'ringing' on sharp edges despite being 'generally good'. I'm sure this was explained in the manual in a list of filter/interpolation options for the general case but I can now only find one reference to it in Scene Linear painting: "Speaking of filters, when using the transform tool, you should also avoid using lanczos3, it’ll give a weird black halo to sharp contrasts in scene-linear."
Yes, it is supossed to be this way with the lanczos filter, the ring artifacts are a side-effect of how the lanczos filter applies a little bit of edge sharpning to get it's sharp results.