Last modified: 2008-07-30 21:34:51 UTC

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Bug 6205 - Resize to thumbnail is ugly for PNG with transparency/alpha channel
Resize to thumbnail is ugly for PNG with transparency/alpha channel
Status: RESOLVED WORKSFORME
Product: MediaWiki
Classification: Unclassified
File management (Other open bugs)
unspecified
PC other
: Normal normal (vote)
: ---
Assigned To: Nobody - You can work on this!
http://nl.wikipedia.org/wiki/Gebruike...
:
Depends on:
Blocks:
  Show dependency treegraph
 
Reported: 2006-06-05 13:10 UTC by Arp Kruithof
Modified: 2008-07-30 21:34 UTC (History)
1 user (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---


Attachments

Description Arp Kruithof 2006-06-05 13:10:13 UTC
== Bug ==
When resizing a fairly optimized (few bits per pixel) PNG for thumbnail display
in an Wikipedia article a few unpleasant things happen, especially when the
original has transparency (alpha channel) enabled:

# The image becomes very ugly.
# The resized image that will be transmitted by the server has a byte count that
is way larger than the 'big' original and up to ten times larger than it
''could'' be.

== Related ==
'''Note:''' The 'resize' has larger byte count than original is same as: [[Bug
1218]] and [[Bug 5211]]

The "'''ugly''' with alpha channel" issue ''might'' be related to [[Bug 234]],
but the issue descriped in this report is '''not limited to Internet
Explorer''', in fact it has ''nothing'' to do with the browser at all.

== Examples ==
For example page visit:
http://nl.wikipedia.org/wiki/Gebruiker:Pudding4brains/PNG-Bug
Comment 1 gpvos 2006-06-11 13:50:36 UTC
Maybe upgrading to a newer version of ImageMagick might help. I have version 6.2.5 04/21/06 Q16 here 
at home, and using the same options that MediaWiki uses (that should be "convert -coalesce -resize 
200x328! -depth 8", right?), I get a nice PNG (although still many bytes).

As for the byte count, I haven't found options for ImageMagick yet that force it to retain a bit 
depth of 4 bits. This might be something to request there. (Actually, using -depth 4 on the image 
with alpha gives something even uglier than what was reported; without alpha is OK.)
Comment 2 Tim Starling 2006-06-11 23:25:09 UTC
We upgraded the existing servers to 6.2.6 Q8 a while ago, but unfortunately the
setup script wasn't changed, so new servers were installed with whatever was in
the repository, often 6.2.2 Q16. I've fixed this now, they're all running 6.2.6 Q8.
Comment 3 Arp Kruithof 2006-06-12 00:16:28 UTC
Hi Tim, looking at http://nl.wikipedia.org/wiki/Gebruiker:Pudding4brains/PNG-Bug
I would tend to conclude that the either the server is not properly upgraded
(yet?) or the new version ImageMagick doesn't solve the problem?

In addition to the 200px resize allready present I've tried to display 100px,
198px, 202px and 300px resizes (to maybe avoid my not seeing any improvement
being caused by a server side cache (??) but _only_ the 300px version is
dispalyed - the others are not ???! Confused ... 
Comment 4 Tim Starling 2006-06-12 02:55:27 UTC
Sorry, didn't mean to mark it resolved. There's lots of problems here and the upgrade 
would only affect some of them.
Comment 5 Arp Kruithof 2006-06-12 21:25:04 UTC
(In reply to comment #4)
> Sorry, didn't mean to mark it resolved. There's lots of problems here and the
upgrade 
> would only affect some of them.
Okay, no problem - thanks for reopening :)

Comment 6 Aryeh Gregor (not reading bugmail, please e-mail directly) 2008-07-29 21:05:50 UTC
(In reply to comment #0)
> The "'''ugly''' with alpha channel" issue ''might'' be related to [[Bug 234]],
> but the issue descriped in this report is '''not limited to Internet
> Explorer''', in fact it has ''nothing'' to do with the browser at all.

Going to repurpose the bug to this, the size issue is already covered elsewhere.
Comment 7 Brion Vibber 2008-07-30 21:34:51 UTC
As far as I know no current issue remains. Please provide an example image file and description (original page linked no longer exists).

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