Last modified: 2012-07-31 12:10:54 UTC
Some JPEG images on Wikimedia Commons are getting their thumbnails rendered incorrectly when the thumbnail width is less than 85% of the original. It looks like the black and gray areas are missing or rendered incorrectly. Examples: http://commons.wikimedia.org/wiki/File:Feedbackims.jpg: 550x238 Bad thumbnail http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Feedbackims.jpg/467px-Feedbackims.jpg Good thumbnail http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Feedbackims.jpg/468px-Feedbackims.jpg http://commons.wikimedia.org/wiki/File:Wikiresponsecurves1.jpg: 1832x3460 Bad thumbnail: http://upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Wikiresponsecurves1.jpg/1557px-Wikiresponsecurves1.jpg Good thumbnail http://upload.wikimedia.org/wikipedia/commons/thumb/8/8e/Wikiresponsecurves1.jpg/1558px-Wikiresponsecurves1.jpg I've tried these at a variety of resolutions, and the results seem to be consistent: widths below 85% produce incorrect thumbnails, while widths above 85% produce good thumbnails. This appears to be a recent problem. A related file (uploaded by the same author, http://commons.wikimedia.org/wiki/Special:Contributions/Nbisaria, as the other two files) has a correct (cached) 300px thumbnail but broken 200, 299, 301 and 561px thumbnails: http://en.wikipedia.org/wiki/File:Ferrell.jpg: 661x389 Bad thumbnail: http://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Ferrell.jpg/561px-Ferrell.jpg Good thumbnail: http://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Ferrell.jpg/562px-Ferrell.jpg, http://upload.wikimedia.org/wikipedia/commons/thumb/a/a5/Ferrell.jpg/300px-Ferrell.jpg (probable cached)
+self CC
Possibly related problem: in Safari (Mac OS X), all of the above-linked thumbnails (including the cached 300px Ferrell thumbnail) are showing up with black backgrounds (instead of white), which makes them very hard to read.
That is weird. Also looks like MW's exif support isn't properly extracting exif info from that file (that or it has none which would be even weirder)
Found that the images were all CMYK, looks like this has been previously reported. *** This bug has been marked as a duplicate of bug 24854 ***
The behaviour reported here differs from bug 24854 in some respects (resolution mattering, and both the grey/black totally dissapearing without any other colour artifacts), but you're still probably right its a dupe.
