[Bug 24889] Moiré: Can we do anything about it?
https://bugzilla.wikimedia.org/show_bug.cgi?id=24889 --- Comment #5 from Brion Vibber br...@wikimedia.org 2011-09-15 22:55:29 UTC --- Created attachment 9065 -- https://bugzilla.wikimedia.org/attachment.cgi?id=9065 Sample scale-downs using ImageMagick gimp Adding a Gaussian blur on the original image before scaling seems to work wonders for this engraving; a 10x10 blur in Gimp for 310px or a 2x2 blur for 1600px both come out looking fairly smooth. Blurring may however be relatively slow, especially on large images; it's probably not the best idea to turn it on as a default. However I notice I actually get very good results using ImageMagick's '-resize' mode instead of '-thumbnail'. By default -resize applies a Mitchell filter; I can also apply '-filter Gaussian' which looks not quite as sharp. The -filter option seems to be ignored by -thumbnail; or if it is applied it looks like it happens after a much more primitive resampling which'll be what gives us the heavy moire: http://www.imagemagick.org/Usage/resize/#thumbnail Of course part of the reason we use -thumbnail is probably because it's fast because it doesn't do all that filtering at full resolution. :P Being able to flip particular images into the slower, more filtered scaling may actually be useful -- I suspect a simple on/off will be sufficient. But I don't know what performance impact it'll have; very large source images with high contrast are the target group, but very large source images are the exact ones that are slow and use lots of memory to resize. :( -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email --- You are receiving this mail because: --- You are the assignee for the bug. You are on the CC list for the bug. ___ Wikibugs-l mailing list Wikibugs-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
[Bug 24889] Moiré: Can we do anything about it?
https://bugzilla.wikimedia.org/show_bug.cgi?id=24889 --- Comment #4 from Derk-Jan Hartman hart...@videolan.org 2010-09-23 18:56:20 UTC --- http://commons.wikimedia.org/wiki/File:Rajpoots_2-scaled.tif Another example for people who will want to work on this and test scaling routines. -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email --- You are receiving this mail because: --- You are the assignee for the bug. You are on the CC list for the bug. ___ Wikibugs-l mailing list Wikibugs-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
[Bug 24889] Moiré: Can we do anything about it?
https://bugzilla.wikimedia.org/show_bug.cgi?id=24889 --- Comment #3 from Adam Cuerden cuer...@gmail.com 2010-08-28 10:15:26 UTC --- Ah, well. Figured it was going to be something like that. -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email --- You are receiving this mail because: --- You are the assignee for the bug. You are on the CC list for the bug. ___ Wikibugs-l mailing list Wikibugs-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
[Bug 24889] Moiré: Can we do anything about it?
https://bugzilla.wikimedia.org/show_bug.cgi?id=24889 --- Comment #1 from Adam Cuerden cuer...@gmail.com 2010-08-21 12:17:48 UTC --- Note that image may be a good test: MOST thumbnails have some sort of Moiré in the sky. -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email --- You are receiving this mail because: --- You are the assignee for the bug. You are on the CC list for the bug. ___ Wikibugs-l mailing list Wikibugs-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikibugs-l
[Bug 24889] Moiré: Can we do anything about it?
https://bugzilla.wikimedia.org/show_bug.cgi?id=24889 Derk-Jan Hartman hart...@videolan.org changed: What|Removed |Added CC||hart...@videolan.org --- Comment #2 from Derk-Jan Hartman hart...@videolan.org 2010-08-21 12:36:29 UTC --- Sure, if we start scaling each image by hand, picking the best algorithm. All is a trade off between speed, quality and sharpness. And the bigger the image, the worse the effects can be of course. See also: http://www.imagemagick.org/Usage/resize/#filter Specifically: http://www.imagemagick.org/Usage/resize/#best_filter -- Configure bugmail: https://bugzilla.wikimedia.org/userprefs.cgi?tab=email --- You are receiving this mail because: --- You are the assignee for the bug. You are on the CC list for the bug. ___ Wikibugs-l mailing list Wikibugs-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikibugs-l