[garblegarble]

>The model uses a GAN which does not learn the exact PDF. So not lossless, but as you can see from the images it gets extremely visually accurate results.

Yes, I understand this is a lossy compression method - what I was proposing is to have the compressor as a final pass take the predicted output image, and subtract it from the original pixels. This gives you a delta between the predicted image and the original image. You can then compress that delta losslessly, and store it alongside the output of this model - if the predicted image is close enough to the original image then you've significantly reduced the amount of entropy in the delta, making it highly compressible.

This is how some domain-specific lossless compression algorithms work, e.g. DTS-HD Master Audio