images are resized using incorrect color space
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	• bzimport
	Oct 27 2008, 5:59 AM

Description

Author: richard.mitton

Description:
Hi,
(apologies if this is a dupe, the search function sucks)

When the wiki resizes an image, it seems to do so using a wacky color space.

For example, see this original image:
http://upload.wikimedia.org/wikipedia/en/e/e0/Penny_Harvest_Field_2007.jpg

and then compare to this automatically generated one:
http://en.wikipedia.org/wiki/Image:Penny_Harvest_Field_2007.jpg

Notice the red window in the background - it's clearly changed to a much lighter shade.

This is not a browser issue, as you can download the image and verify in other programs.

Disclaimer: I'm testing on a Mac, using Safari. It's possible on some browsers the color space may be ignored for both images, thus hiding the bug.

Version: unspecified
Severity: minor

Details

Reference: bz16140

Related Objects

Mentioned In: T26768: PNG thumbnails of SVG images should use sRGB chunk

Event Timeline

• bzimport raised the priority of this task from to Medium.Nov 21 2014, 10:22 PM

• bzimport added a project: MediaWiki-File-management.

• bzimport set Reference to bz16140.

• bzimport added a subscriber: Unknown Object (MLST).

• bzimport created this task.Oct 27 2008, 5:59 AM

Firefox 3.0.3 ignores the color space, and appears to show both images about the same. I can confirm that Safari shows the original image a little darker (eg with color correction), though honestly most lay people will never notice the difference. ;)

Not sure offhand what would be required to pass the color space information through to the thumbnail.

richard.mitton wrote:

For another example, compare

original:
http://upload.wikimedia.org/wikipedia/en/b/b8/Highsmithvenicecanals.jpg

vs. thumbnail:
http://en.wikipedia.org/wiki/Image:Highsmithvenicecanals.jpg

On my monitor at least, the difference is very noticeable. The thumbnail looks very pale and washed out.

The example image given above was moved to Commons:

original:
http://upload.wikimedia.org/wikipedia/commons/b/b8/Highsmithvenicecanals.jpg

preview:
http://commons.wikimedia.org/wiki/File:Highsmithvenicecanals.jpg

That said, the original image looks terrible with Firefox 3.5.6.

richard.mitton wrote:

Perhaps the best solution might be to force-convert all images to sRGB upon upload?

When using a Mac at least, it's very common for photos to be generated using something like Adobe RGB, and the uploader might not even realise that most non-Safari browsers won't show these properly.

color profiles should now be preserved by the thumb system (Bug 19960). That doesn't negate that some browsers don't interpret them at all of course.