(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:
and then compare to this automatically generated one:
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.