GNOME Bugzilla – Bug 735071
Scaling with NoHalo or LoHalo repeats parts of the image
Last modified: 2014-09-10 22:18:48 UTC
Created attachment 283920 [details] Image window just before scaling Scaling an image with an alpha channel using NoHalo or LoHalo produces artifacts where part of the image is repeated, at least at some image sizes. To reproduce: - Open a JPG photo or similar image. - Choose a small piece of it by cropping it to 350x300. - With ellipse select, select a circle inside it of size 250x250 - Add alpha channel - Select->Invert - Edit->Clear (now you have a circular image surrounded by transparency) - Select->None - Image->Scale to 150x150, NoHalo or LoHalo I'll attach screenshots before and after scaling. Scaling with Cubic is unaffected. I've seen this regularly on images with alpha, but never on an image without alpha. I reported this on #gimp two weeks ago and massimo said it had been mentioned on #gegl and was likely from the same cause as bug 732428, but it's been two weeks and I can't find any reported bug that seems similar or gives instructions on how to reproduce. Bug 592628 and bug 734378 look like they might be related, but they sound fairly subtle and specific, not an obvious large error like this one.
Created attachment 283921 [details] Screenshot of image window after scaling
Duplicate of #734378?
Bug 734378 is about scaling, and about vertical stripes, which is exactly what I see in the screenshot in comment 1, it's simply just one stripe because the image is small. Resolving as duplicate. *** This bug has been marked as a duplicate of bug 734378 ***