Page MenuHomePhabricator
Create Task
Maniphest T71155

PNG thumbnail get smudgy and streaky (near garbled)
Closed, ResolvedPublic
Actions

Description

The png [[File:Dpm2.png]] has a weird graphical artifact; size 640 (× 272) pixels https://upload.wikimedia.org/wikipedia/commons/thumb/archive/d/dd/20140805183822%21Dpm2.png/640px-Dpm2.png (the actual upload is also not fully fixed with transparency workaround), the C2–C3 bond of 2-methoxy-1-propanol (the vertical blue line in the top-left structure) has a ghost to its right. At larger renderings (2-3 px are sufficient), it disappears, so it could just be a wikimedia renderer goof or a hidden problem in the image itself. (by -- user: DMacks)

Version: 1.24rc
Severity: minor

Details

Reference
bz69155

Related Objects
Search...

StatusSubtypeAssignedTask
 OpenNoneT43371 Thumbnail/imagescaler (tracking)
 OpenNoneT108517 PNG thumbnails issues (tracking)
 ResolvedNoneT71155 PNG thumbnail get smudgy and streaky (near garbled)

Event Timeline

• bzimport raised the priority of this task from to Medium.Nov 22 2014, 3:37 AM
• bzimport added a project: MediaWiki-File-management.
• bzimport set Reference to bz69155.
• bzimport added a subscriber: Unknown Object (MLST).
Perhelion created this task.Aug 5 2014, 8:58 PM
• Gilles added a comment.Aug 5 2014, 10:10 PM

The line artifacts are very visible at higher resolutions:

https://upload.wikimedia.org/wikipedia/commons/thumb/archive/d/dd/20140805183822!Dpm2.png/1500px-Dpm2.png

https://upload.wikimedia.org/wikipedia/commons/thumb/archive/d/dd/20140805183822!Dpm2.png/3500px-Dpm2.png

• brooke added a comment.Aug 6 2014, 9:09 AM

Problem with VPSscaler?

Perhelion added a comment.Aug 10 2014, 11:52 AM

This case seems be very rare!? I found until yet no other picture (with exception of small thumbs with raster pattern, which get very big). But I've also not very intensively searched. So this bug may be negligible?

Perhelion added a comment.Nov 14 2014, 6:10 PM

Another example, there are some slightly visible vertical stripes. The image is indexed with only 6 colors. [[File:Wappen_Samtgemeinde_Bevensen-Ebstorf.png]]

Bawolff added a comment.Nov 14 2014, 6:27 PM

(In reply to Brion Vibber from comment #2)

Problem with VPSscaler?

Yes I think so. It looks similar to artifacts observed with tiffs when using vips shrink (instead of im_shrink) with non-integer shrink factors. Notice the lack of artifacts when using integral scale factors like https://upload.wikimedia.org/wikipedia/commons/thumb/archive/d/dd/20140805183822!Dpm2.png/2357px-Dpm2.png

That said, previously these types of artifacts were only observed on tiff files. Based on comment 4, maybe only observable on indexed pngs?

Perhelion added a comment.Nov 14 2014, 6:48 PM

(In reply to Bawolff (Brian Wolff) from comment #5)

(In reply to Brion Vibber from comment #2)

... Based on comment 4, maybe only observable on indexed pngs?

Yes I think so. I tested the "integral scale factors" and yes it's depending on the original resolution (unusually / odd pixel dimension seems a part of this bug).

For example 2309 is Prime number (so this should be the last good render resoltion): http://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Wappen_Samtgemeinde_Bevensen-Ebstorf.png/2309px-Wappen_Samtgemeinde_Bevensen-Ebstorf.png

Renderings lower than 400px seems ok.

• Gilles added a project: Multimedia.Nov 24 2014, 3:20 PM
Perhelion mentioned this in T53400: Improve quality of scaled PNGs with Vips for all sizes.Jul 16 2015, 9:19 PM
McZusatz merged a task: T108494: small grey line artifacts on large png (probably VIPS non-integral scale related).Aug 9 2015, 1:13 PM
McZusatz added subscribers: McZusatz, Aklapper, Matanya.
Restricted Application added a subscriber: Steinsplitter. · View Herald TranscriptAug 9 2015, 1:13 PM
McZusatz added a parent task: T108517: PNG thumbnails issues (tracking).Aug 9 2015, 1:22 PM
McZusatz removed a parent task: T43371: Thumbnail/imagescaler (tracking).
McZusatz added a comment.Aug 9 2015, 1:32 PM

Archive of one test case:

3500px-Dpm2.png (1×3 px, 285 KB)

CFCF subscribed.Aug 16 2015, 10:12 PM
Jdforrester-WMF moved this task from Untriaged to Backlog on the Multimedia board.Sep 4 2015, 6:35 PM
MarkTraceur unsubscribed.Jan 27 2017, 10:11 PM
Restricted Application added a project: Commons. · View Herald TranscriptJan 27 2017, 10:11 PM
zhuyifei1999 moved this task from Incoming to Thumbnail and file renderings on the Commons board.Jul 25 2017, 9:47 AM
Aklapper mentioned this in T192744: PNG thumbnail looks significantly blurrier than JPG thumbnail.Apr 22 2018, 8:59 PM
AntiCompositeNumber subscribed.May 21 2020, 3:10 AM

Thumbnail generation on Wikimedia wikis is now handled by Thumbor instead of MediaWiki. Since this task was filed, there have also been several updates to the upstream image libraries. I don't see anything wrong with the thumbnails now. Does this problem still exist?

AntiCompositeNumber closed this task as Resolved.Aug 10 2020, 1:00 AM
Content licensed under Creative Commons Attribution-ShareAlike (CC BY-SA) 4.0 unless otherwise noted; code licensed under GNU General Public License (GPL) 2.0 or later and other open source licenses. By using this site, you agree to the Terms of Use, Privacy Policy, and Code of Conduct. · Wikimedia Foundation · Privacy Policy · Code of Conduct · Terms of Use · Disclaimer · CC-BY-SA · GPL