Hi guys. I tried to upload a new emoji but both size and colors seemed to be a bit off. So i tried the following:
After that, i opened both images in new tabs (so there is no css involved) and I have this result:
(left image is the uploaded one)
We downsize uploaded emoji to make sure they fit in a 60x60 square.
Maybe one of the Image Magick option is altering the emoji?
But… Why? Since the default (apple) emoji are 64x64 and emoji one (i think) are 74x74, it wouldn’t make more sense to have them resized to the current emoji scheme base size? 
This might be related to Image Magick messing up black and white images too.
Maybe Image could do with a little less Magicks
What, like ImageScience? 
In all seriousness, tho, I’m guessing that the -thumbnail operation is a bad choice. It focuses filesize over everything else, and while this may be fine for actual thumbnails, it’s not desireable for emojis (which are small enough anyways).
Thanks @iamntz for reporting that issue. I updated the code so that we only downsize to 100x100 using the resize option instead of thumbnail. 
https://github.com/discourse/discourse/commit/a87083fa7641267339e06a77773601594570d0fd
@zogstrip can you verify we don’t have any lingering issues here? Maybe upload emoji to test?
Here’s one:
Here’s another 2.
They look fine to me.