I've done some analysis, and it seems that Endchan rewrites every single image that I post. If true, this is bad and is worse than what 4chan does. Here's a test of 2 PNGs, 2 JPGs, and 1 GIF with links to original images below. (Endchan image files are named by MD5 hash + MIME type.)

1. JPG, MD5: 8d004ae26a49089a16829efcc6f5bf43
ipfs://bafkreie4stauzmifnmz2fx7xuqkeqvujoifkeluxvpvc2nus3s5e64goky
https://sabrig1480.xyz/ZeGIZM2yd_OBeKrO4ylKO6EgdQB_z-YTrUkYcd4BYvw

2. PNG, MD5: 55c556f146894d9df78e42a9586631d4
ipfs://bafkreidovqh5kvbaorl2svpisxu7gzepesrk5ltefoujxxaf373t4o5bnu
https://aralper.xyz/c4kAUtwRbucNVG33igsMpVn9Zmdb6EPM5gtTCRqD2VU

3. JPG, MD5: aa6ca96c19b66babee493164566b0115
ipfs://bafkreidkvw774zublzkumuuukocn43ri6zemhvn7y67c37xzuba4wudhv4
https://imtran.site/4HP_yX8wICqU7tg5nLUJaY4Hfe0rsr7uYfud3UyQ-8M

4. GIF, MD5: b131704afaf666ed659d3b886787e0e0
ipfs://bafkreidh5bptl4ayjp3w3e4zd74ei7ayezmn7gind3cs5ps7gp7acfuqv4
https://ahnetd.online/tHd2gq4Ig479tpZ49e3KkT2lr1WTlzePGOSSX74kbhs