We’ve just launched a Discourse forum. As part of that we created custom logos. When we tweet a link from the forum on Twitter, the 144x144 square logo isn’t rendering properly. It’s picking up some black coloring artifacts. The file looks fine from within the Discourse environment.
I’ve uploaded a screenshot to show what I mean. There shouldn’t be any black on this logo. It should just be blue/orange with a white background:
I suspect twitter has cached the transparent PNG you were using, if I put the URL into this then it displays the new JPG correctly: https://cards-dev.twitter.com/validator
Yep, it fixed itself once the cache updated. For me, it was about 12 hours before it corrected itself.
I suppose there still is the question of why the transparent png file didn’t render properly, but that was easily circumvented by converting the image to a jpg file.