It's a somewhat active inverse problems research subfield https://github.com/MenghanXia/ReversibleHalftoning
replyThat 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.
replyDither loses information, so perfectly reversible might be an unreasonable goal. But I bet you could train or fine-tune a denoiser to do a really good job. This might make a cool paper, if there’s anything at all non-standard or surprising you discover along the way.
replyWhen I mentioned "perfectly reversible", I meant the FFT itself. You run the FFT. You run the inverse FFT. Because the FFT was quantized to 0-255, you end up with a lot of stuff that doesn't belong in the image.
replyGotcha, that’s true. There’s gradations of non-reversible. FFT in practice is still not perfectly reversible, even if you use floats and don’t quantize to 8-bit. Anyway, yeah, dither will be even more non-reversible, but given how good today’s denoisers are, I bet de-dither could be pretty good if it was attacked with the same level of rigor as denoise has been.
replyNo, although AI gets really close. Dithering represents adding noise to an image and also represents doing a lossy type of compression.
replyDo you want to undither, or un-half-tone, like the images in TFA?
replyUnhalftoning is called descreening.
I use this: