Sixel is a fun side quest as well, if you want to encode it on your own. You get to work on a color quantization and/or dithering algorithm in $CURRENT_YEAR.

And if you're doing text with images, integrating both Sixel and Kitty is especially painful because they have completely different display models.

(In particular, Sixel is cell based, so you get Z-ordering for free - with the caveat that writing text on top of images destroys the cells.

Meanwhile, Kitty has Z-ordering, but it's per-image, so e.g. to draw a menu on top of an image that partially covers text, you must send a new image with space for the menu erased...)

For those who are interested, the best resource I've found on this is the notcurses author's wiki: https://nick-black.com/dankwiki/index.php/Theory_and_Practic...