Patent ID: 8861038

Claim:
A method for printing an image comprising colour pixels by deriving from the image a coloured dot pattern for applying dots on print positions in a printer comprising a black colorant for printing black dots, the printer comprising further colorants that, printed in combination, also result in black dots, the method comprising the steps of: separating a pixel colour into a number of printer colorant amounts; determining an amount of black that results from coinciding printer colorants; establishing an amount of black colorant substituting a fraction of the coinciding printer colorants based on the determined amount of black; deriving a total dot coverage for every pixel of the image from a sum of at least three amounts of colorants, including the amount of black colorant; establishing an image dot pattern in accordance with the total dot coverage, wherein a perceived error between the image pixels and the image dot pattern is minimized; establishing a dot colour, selected from the printer colorants, for every dot in the image dot pattern in accordance with the amounts of printer colorants in the image, thereby obtaining a coloured dot pattern; swapping a number of dot colours in order to minimize the perceived error between the colour of the pixels in the image and the coloured dot pattern; adding dots of colorants that are not comprised in the total dot coverage by either independently deriving a halftone pattern for a colorant or adding dots on print positions not yet comprising a dot according to the coloured dot pattern, thereby obtaining a printable dot pattern for each colorant in the printer, and applying colorant ink on print positions according to the dots in the printable dot pattern.