JPEG is actually ~12 bits deep, it's just that all the decoders decode it to 8 bit YCbCr, and on top of that cause extra loss by 8-bit YCbCr->RGB conversion. It

JPEG is actually ~12 bits deep, it's just that all the decoders decode it to 8 bit YCbCr, and on top of that cause extra loss by 8-bit YCbCr->RGB conversion. It's possible to compile libjpeg with a 16-bit color pipeline, but it's a hassle, so nobody does that.