[jeremyscanvic]

It's a somewhat active inverse problems research subfield https://github.com/MenghanXia/ReversibleHalftoning

[Dwedit]

That one does not seem to be an undither project, it appears to be a special way to encode chroma information within a monochrome dithered image. NTSC television also encodes chroma within a grayscale signal, but that's different than black and white only.