You can force Twitter to post the “raw” quality of your pics by adding one (1) pixel of transparency in the image.
Twitter uses some algorithm to compress images into .jpg, but it cannot do that if there’s transparency involved in the image, forcing it to be .png in its full quality. Literally one singular pixel ANYWHEREcounts for this, it can be on a corner if you don’t want it to be bothersome.
Figured some folks might be interested in this, considering Tumblr no longer supports the _raw trick.
For the sake of example instead of hearsay, I’ve posted a comparison in my Twitter here, but will also explain here. All images are 2000x2000px versions of my logo you can see on the top left of this post: