Halftone to continuous-tone conversion of error-diffusion coded images

The problem of reconstructuring a continuous-tone (cotone) image from its error-diffused halftoned version is presented. The authors present a POCS (projection onto convex sets)-based iterative nonlinear algorithm for this problem, and show simulation results that compare the performance of the algorithm with that of conventional linear lowpass filtering. It is found that the proposed technique results in subjectively superior reconstruction. As there is a natural relationship between error diffusion and sigma-delta modulation, the proposed reconstruction algorithm can also be applied to the decoding problem for sigma-delta modulators.<>