Artifacts on geometric avatar

[lhinderberger]

• Gitea version (or commit ref):
• Git version: 1.13.0+dev-484-g1d47a2575 (try.gitea.io)
• Can you reproduce the bug at https://try.gitea.io:
  • Yes: https://try.gitea.io/knut

Description

Hello everyone. I want to bring your attention to a rather minor, but optically very unpleasing bug:

When creating an account, I noticed that the avatar had bad-looking artifacts after uploading (see attached screenshots). I suspect that this is due to a scaling algorithm that performs poorly on geometric shapes like circles.

I’ve attached the original image and a screenshot for reference.

Thank you!

Screenshots

Screenshot from codeberg-test (another instance where this also occurs):

Original avatar:

[6543]

looks like it's present in v1.12.x too

[6543]

this issue is has to do how we resize things ...

gitea/modules/avatar/avatar.go

Line 92 in 43c303d

img = resize.Resize(AvatarSize, AvatarSize, img, resize.NearestNeighbor)

Wikipedia has interesting infos: https://en.wikipedia.org/wiki/Image_scaling

I thin we just have to switch from NearestNeighbor to Lanczos3/Bilinear/Bicubic...
-> https://github.com/nfnt/resize

or switch to a better resize lib

[6543]

source: https://codeberg.org/Codeberg/Community/issues/243