High-speed single-pass printing using combined dither pattern

A method of processing a contone image for single-pass printing using a printing system comprising at least first and second aligned printheads supplied with a same ink, the second printhead being downstream of the first printhead, the method comprising the steps of:

• providing the contone image for one ink channel at a first resolution in a printing direction;
• selecting a dither pattern from the group either one of:
• (a) a combined dither pattern comprising a combination of a first dither pattern for the first printhead and a second dither pattern for the second printhead, the first dither pattern being different than the second dither pattern;
• or (b) a third dither pattern for both the first and second printheads;
• dithering the contone image using the selected dither pattern to provide a full halftone image at the first resolution;
• dividing the full halftone image into at least first and second halftone images at a second resolution in the printing direction, the second resolution being less than the first resolution;
• and
• sending the first and second halftone images to respective first and second printheads for printing,
• wherein the selection of the dither pattern from either (a) the combined dither pattern, or (b) the third dither pattern is based on relative printhead alignment between the first and second printheads.