https://bugzilla.wikimedia.org/show_bug.cgi?id=22041
Summary: Animated GIFs thumbnailed as still images even when
smaller than the cutoff limit
Product: MediaWiki
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: Normal
Component: Images and files
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected], [email protected]
Recently thumbnailing of GIFs was re-enabled on Wikimedia sites after new code
was added to count the frames in animated GIFs.
Reading the code it appears that currently two checks are intended to determine
whether a GIF should be thumbnailed.
First, if height*width*frames > $wgMaxImageArea then Bitmap.php aborts and no
thumbnail is attempted.
Secondly, if height*width > $wgMaxAnimatedGifArea then Bitmap.php returns only
the first frame.
The default values for these parameters are 12.5 million and 1 million
respectively, and they do not appear to have been changed in Wikimedia's
CommonSettings.php file.
Now there appear to be two issues here. First, since we are now counting GIF
frames, is there a reason for still having the second check? My understanding
is that the lower limit was added in the days before frame counting to trap
large animated GIFs with many frame before they could crash the thumbnailer.
Now that we count frames, isn't the first check sufficient for that?
Secondly, and the more immediate reason for this bug report, it appears that
Wikimedia is showing single frames for some animated GIFs even if their size is
definitely less than one megapixel. For example:
http://en.wikipedia.org/wiki/File:Phenakistoscope_3g07690a.gif
http://en.wikipedia.org/wiki/File:Swimapod4.gif
http://commons.wikimedia.org/wiki/File:Action_potential_propagation.gif
Each of these is an animated GIF with an area less than 1 megapixel but the
thumbnails shown on the image description page (and anywhere else thumbnails
appear) show only a still image. Hence they appear to have triggered the
second conditional even though they shouldn't have if the sizes are being
accurately handled and the limit is still set at the default.
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