Perhaps the optimal technique would be to write a function which halftones a greyscale image, and then use optimisation to find a greyscale image which reproduc

Perhaps the optimal technique would be to write a function which halftones a greyscale image, and then use optimisation to find a greyscale image which reproduces the input image when halftoned. This feels like an expectation–maximization kind of problem, but i can't give a rigorous argument for why.