Method of printing and printer

A computer program for controlling operation of a printer, the printer including a number of print heads comprising at least a first row of fluid ejection nozzles and at least a second row of fluid ejection nozzles, the first and second rows of fluid ejection nozzles providing fluid of a first type and fluid of a second type, respectively, the printer further including a printer controller executing the computer program, the computer program comprising modules for:

• receiving print data describing an image to be printed;
• assigning respective parts of the image to be printed to the first and second rows of fluid ejection nozzles;
• generating a first mask and a second mask;
• applying the first mask to the first row of fluid ejection nozzles and the second mask to the second row of fluid ejection nozzles for printing with selected nozzles of each of the rows of fluid ejection nozzles during a number of passes corresponding to a multi-pass printing mode, wherein each mask specifies a frequency at which the nozzles of the associated row of fluid ejection nozzles are fired;
• and
• printing the image;
• wherein each of the masks comprises a mesa portion and first and second ramp portions at both sides of the mesa portion, wherein the mesa portion of the first mask includes at least a first peak and the mesa portion of the second mask includes at least a second valley, the first peak overlapping with the second valley;
• and
• wherein the peaks and valleys in the mesa portions of the first and second masks have an amplitude smaller than an amplitude of the first and second ramp portions at the sides of the mesa portions.

A printer including

• a number of print heads comprising a number of nozzle trenches, including a first nozzle trench and a second nozzle trench ejecting fluid of a first type and fluid of a second type, respectively;
• and
• a printer controller including a control program to control ejection of printing fluid from the print heads and applying a first masks to the first nozzle trench and a second mask to the second nozzle trench to print with selected nozzles of each nozzle trench during a number of passes corresponding to a multi-pass printing mode;
• wherein each of the masks comprises a mesa portion and first and second ramp portions at both sides of the mesa portion,
• wherein the mesa portion of the first mask includes at least two first peaks and a first valley between the two first peaks and the mesa portion of the second mask includes at least two second valleys and at least one second peak between the two second valleys, the peaks of one mask overlapping with the valleys of the other mask and the valleys of the one mask overlapping with the peaks of the other mask;
• wherein the peaks and valleys in the mesa portions of the first and second masks have an amplitude smaller than an amplitude of the first and second ramp portions at the sides of the mesa portions.