Method of non-overlapping color printing

A multi color printing method employing a color printer capable of non-overlapping color printing using M non-black colorants and a black colorant, where M is one or more, comprising the steps of:

• a) providing a digital color image having multi-bit color pixels;
• b) separating the digital color image into three multi-bit color primary components and one multi-bit black component;
• c) converting each multi-bit component into a 1-bit component by applying nearly equal threshold values to respective color components of an n-tuple of neighboring pixels each pixel in the n-tuple having a unique designation N;
• d) assigning a single printer colorant to each output image pixel based on the 1-bit color components by,
• 1) if the 1-bit Black component is a one, set the output pixel to print Black,
• 2) if the combination of non-black 1-bit color components appears as a color which is available as a printer colorant, set the output pixel to the available printer colorant,
• 3) if the combination of non-black 1-bit color components appears as a color which is not available as a printer colorant, and if the pixel is the Nth pixel in an n-tuple, set the output to the Nth member of a combination of N-1 printer colorants and no colorant which when viewed near each other appear as the combination of the non-black 1-bit color components, and
• 4) if all of the 1-bit color components are 0's, set the corresponding output pixel to print no colorants;
• and
• e) printing the image using the assigned colorants.

A computer program product, comprising:

• a) a computer readable storage medium, such as a memory device, a compact disc or a floppy disc, and
• b) a computer program stored on the disc for receiving a digital color image having multi-bit color pixels and causing a computer connected to a color printer capable of non-overlapping color printing using M colorants to print a color image, where M is greater than two, by performing the steps of:
• 1) separating the digital color image into three multi-bit color primary components;
• 2) converting each multi-bit component into a 1-bit component using a digital halftoning technique;
• 3) assigning a single printer colorant to each output image pixel based on the 1-bit color components by,
• i) dividing the image into n-tuples, each pixel in an n-tuple having a unique designation N,
• ii) assigning N-member combinations of N-1 printer colorants and no colorant that appear as combinations of 1-bit color components, and
• iii) setting an output to the Nth member of an N-member combination based on the corresponding combination of 1-bit color components;
• and
• 4) sending signals representing the assigned printer colorants to the printer for printing the image.