https://bugzilla.wikimedia.org/show_bug.cgi?id=46122
Web browser: ---
Bug ID: 46122
Summary: ImageMagick -fuzz option breaks some animated GIFs
badly
Product: MediaWiki
Version: unspecified
Hardware: All
OS: All
Status: NEW
Severity: minor
Priority: Unprioritized
Component: File management
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected]
Classification: Unclassified
Mobile Platform: ---
The "-fuzz 5%" option, used for scaling animated GIFs to reduce their file size
since r71354, causes some animations to be rather badly corrupted. An
illustrative example is [[File:Pluto_animiert.gif]], which looks fine at full
size but is full of messy artifacts when downscaled.
Rescaling the image on my computer using the exact same "convert" command as
currently used by MediaWiki, but without the "-fuzz 5%" switch, eliminates the
artifacts. It does also increase the file size by about 20%, but this is to be
expected: the *reason* the current thumbnail looks bad is because it's missing
large chunks of image data.
I'd suggest that the -fuzz switch should either be removed entirely, or at
least that the fuzz threshold should be lowered significantly, e.g. to 1% or 2%
at most. (2% seems to be the highest value giving no visible artifacts for
_this_ particular image; of course, some other animations may be even more
sensitive.)
This will increase animated GIF thumbnail sizes somewhat, at least for some
images, but the "-layers optimizeTransparency" switch should still prevent the
truly huge thumbnail sizes that bug 11822 was about.
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