HALFTONING METHOD USING SPACE FILLING CURVES

An image processing system for preparing a document image for printing, each discrete area or pixel in the image described by a signal having a number of possible states greater than can be rendered by a selected printer. In such a system a screening pattern is used which distributes screen values through the image in accordance with the pattern of a space filling curve. Each signal is thresholded against a threshold determined by such ordering and output a signal renderable by the selected printer. A straight forward function relates threshold value in a screen matrix of values and the length of a space filling curve at any point in an image. The nature of certain space filling curves, allows the generation of two reasonably sized lookup tables providing the length of the curve at any point on the page.