Method of and apparatus for printing colour images by the superimposition of a number of separations, using a first half-tone technique optimised for surface reproduction, such as dithering, and a second half-tone technique, differing from the first and optimised for edge reproduction, such as thresholding with error diffusion.
The second half-tone technique is used in edge transitions for pixels of a separation which substantially influences the edge transition, and the said first half-tone technique is used outside the edge transition, while the first half-tone technique is used throughout in the case of pixels of a separation which provide no or minimal contribution to the edge transition.