Printer and computer-readable storage medium for executing multi-pass printing

A printer comprising:

• a print executing unit including:
• a conveying mechanism configured to convey a sheet in a conveying direction;
• a print head having a plurality of nozzles arranged in the conveying direction, each of the plurality of nozzles being configured to eject an ink droplet to form a dot on the sheet;
• and
• a main scanning mechanism configured to execute a main scan by moving the print head in a main scanning direction perpendicular to the conveying direction;
• and
• a controller configured to control the print executing unit to perform a multi-pass printing for printing a target image on the sheet with a plurality of pass processes, the plurality of pass processes forming a plurality of partial images respectively, two partial images formed with successive two pass processes overlapping partially, wherein K-number of active nozzles consecutively arranged are selected from the plurality of nozzles for each of the plurality of pass processes, dot recording rates of the K-number of active nozzles decreasing at an upstream gradient from a nozzle having a maximum dot recording rate among the dot recording rates of the K-number of active nozzles toward a most-upstream nozzle of the K-number of active nozzles in the conveying direction, the dot recording rates of the K-number of active nozzles decreasing at a downstream gradient from a nozzle having the maximum dot recording rate toward a most-downstream nozzle of the K-number of active nozzles in the conveying direction,
• wherein the controller is further configured to control the print executing unit to perform:
• executing an (a)-print process in which the conveying mechanism conveys the sheet and a pass process is executed with Ka number of active nozzles;
• executing, after the (a)-print process is executed, a (b)-print process in which the conveying mechanism conveys the sheet and a pass process is executed with Kb number of active nozzles, Kb being smaller than Ka;
• and
• executing, after the (a)-print process is executed and before the (b)-print process is executed, a (c)-print process in which the conveying mechanism conveys the sheet and at least two pass processes are executed with Kc number of active nozzles, Kc being greater than or equal to Kb and smaller than Ka,
• wherein the at least two pass processes includes:
• a (c1)-pass process with Kc1 number of active nozzles as the Kc number of active nozzles, the downstream gradient of the dot recording rates of the Kc1 number of active nozzles used in the (c1)-pass process being the same as the upstream gradient of the dot recording rates of the Ka number of active nozzles used in the (a)-print process, the upstream gradient of the dot recording rates of the Kc1 number of active nozzles used in the (c1)-pass process being greater than the upstream gradient of the dot recording rates of the Ka number of active nozzles used in the (a)-print process;
• and
• a (c2)-pass process with Kc2 number of active nozzles, the (c2)-pass process being executed after the (c1)-pass process, the upstream gradient of the dot recording rates of the Kc2 number of active nozzles used in the (c2)-pass process being the same as the downstream gradient of the dot recording rates of the Kb number of active nozzles used in the (b)-print process, the downstream gradient of the dot recording rates of the Kc2 number of active nozzles used in the (c2)-pass process being greater than the downstream gradient of the dot recording rates of the Ka number of active nozzles used in the (a)-print process, Kc1 being greater than Kc2.