Author: nneonneo
Description:
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)
Version: 1.20.x
Severity: normal