Artifacts when scaling down with Sinc Lanczos3
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
gimp (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned |
Bug Description
Binary package hint: gimp
Scaling down a solid white field with the Sinc algorithm causes a weird thatched-pattern to appear. I've seen this before but now have an easy way to reproduce. I'm not sure whether the resolutions matter, but here's how I'm currently reproducing:
1. Create a new RGB image filled with solid white, size 5616x3744 (size of 5D Mark II images, what I was editing when I found it)
2. Scale down to 1200x800 using "Sinc (Lanczos3)" Interpolation
3. There will now be a weird thatched-pattern in the image, even though it should be completely #ffffff pixels
I attached the resulting image, saved as a PNG.
ProblemType: Bug
DistroRelease: Ubuntu 10.10
Package: gimp 2.6.10-1ubuntu3
ProcVersionSign
Uname: Linux 2.6.35-22-generic x86_64
Architecture: amd64
CheckboxSubmission: fdbdfcded0c0bb4
CheckboxSystem: edda5d4f616ca79
Date: Sun Sep 26 14:32:20 2010
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100429)
ProcEnviron:
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: gimp
Okay, definitely depends on resolutions, specifically the ratio of original to final size.
For example, I created a white-filled 1600x1600 RGB image and tried scaling to a few different sizes:
1/4: 1600x1600 => 400x400 Okay
1/5: 1600x1600 => 320x320 Artifacts
1/8: 1600x1600 => 200x200 Okay
In my original image I was scaling each side to approximately 1/4.7 the size. So it seems that it's at least around this ratio that the bug appears.