Abstract

We present a new method for retrieving a continuous-tone picture from a digitally created and stored halftone image. It gives substantially better detail than the traditional low pass filtering approach. If the screen parameters are known (or estimated), the pixel value of the halftone (black or white) reveals the possible grey range of the pixel value (above or below the threshold) in the original continuous-tone image. The grey range obtained here is broad. It is narrowed down by logic filtering. The logic filtering is basically an operation combining the grey range data in the neighborhood of a pixel. Its adaptive nature makes it possible to remove the screen effects while retaining the edge information.

© 1989 Optical Society of America