If you're making a tileset with a background texture to use with JJ2's Warp Horizon effect, it can be tedious to have to re-compile your tileset and run JJ2 every time you want to test what it looks like in-game.

I've made a quick-and-dirty online tool you can use to check what your background looks like in JJ2. See it in action at https://www.jazz2online.com/texture_render.php.

Thanks to Violet for a reference implementation of the warp horizon effect.