Printing method and printing system

A printing system comprising:

• a head bar having a first head and a second head disposed at positions, respectively, shifted from each other in a first direction;
• a conveyor configured to convey a recording medium from an upstream side toward a downstream side in the first direction;
• and
• a controller configured to control the head bar and the conveyor, wherein
• the first head is located upstream of the second head in the first direction,
• each of the first head and the second head has a nozzle area in which a plurality of nozzles are aligned at a pitch P along a second direction orthogonal to the first direction, an end part on one side in the second direction of the nozzle area of the first head and an end part on the other side in the second direction of the nozzle area of the second head overlapping in the second direction,
• a plurality of usable nozzles, of the plurality of nozzles of the first head, includes a first nozzle located at the end part on the one side in the second direction and a plurality of first usable nozzles other than the first nozzle,
• a plurality of usable nozzles, of the plurality of nozzles of the second head, includes a second nozzle located at the end part on the other side in the second direction and a plurality of second usable nozzles other than the second nozzle,
• an amount of overlap X1 between a first pixel formed by a liquid droplet ejected from the first nozzle and a second pixel formed by a liquid droplet ejected from the second nozzle is greater than 0 pixels and less than one pixel,
• the controller is configured to perform printing by causing the head bar to repeatedly ejecting liquid droplets from each of the plurality of usable nozzles of the first head and the plurality of usable nozzles of the second head, based on pixel data, while causing the conveyor to convey the recording medium along the first direction, and
• in a case where pixel data for forming a pixel group by liquid droplets ejected from the plurality of first usable nozzles of the first head is different from pixel data for forming a pixel group by liquid droplets ejected from the plurality of second usable nozzles of the second head, the controller is further configured to make the pixel data for forming the first pixel same as the pixel data for forming the second pixel.