One challenge here is that some services will mess with uploaded images. For example an image I created at one point for a puzzle got messed up because the ima

One challenge here is that some services will mess with uploaded images. For example an image I created at one point for a puzzle got messed up because the image host was smart enough to figure out that multiple pallet entries were mapped to the same color and removed/remapped the redundant entries. This saved a ton of image size with no visual difference. Undecodable junk after the end of an image is also in the "can be safely removed" and so may not survive being transmitted via an image host or even email.