Last modified: 2011-04-30 01:20:34 UTC
Created attachment 7592 [details] Generated with: "convert -background white -size 120 testcase.jpg -thumbnail '120x' -depth 8 -sharpen '0x0.4' thumb_wrong.jpg I've found that ImageMagick/convert generates messed-up thumbnails from some kinds of images (mainly truecolor, high-resolution but other kinds may be affected as well). The thumbnails show wrong color portions that might result from wrong (or no) dithering. I tracked down the problem to the "-depth 8" parameter to convert in "includes/media/Bitmap.php", without it, everything looks just fine. A quick possible solution would be, to make this parameter optional. Maybe a dedicated analysis of this bug could result in checking the uploaded image-properties and selectively applying the "-depth 8" option to images where it doesn't harm thumbnail generation. Hope that helps.
Created attachment 7593 [details] Generated with: "convert -background white -size 120 testcase.jpg -thumbnail '120x' -sharpen '0x0.4' thumb_right.jpg"
This is the original file, the thumbnails were generated from: http://localhostr.com/files/431def/testcase.jpg
Tested this on Wikipedia. The problem does not occur on Wikipedia, which indicates that this most likely depends on the version of ImageMagick that you have installed. Consider upgrading to the latest and greatest...
