Inkjet printer and method for determining ink discharging timing

An inkjet printer comprising:

• an inkjet head configured to discharge ink from a plurality of nozzles formed in an ink discharging surface thereof, the plurality of nozzles arranged in a plurality of nozzle rows along a first direction, the plurality of nozzle rows arranged along a second direction that is perpendicular to the first direction and parallel to the ink discharging surface;
• a head moving unit configured to move the inkjet head relative to a recording sheet along the second direction;
• and
• a wave shape generating mechanism configured to deform the recording sheet in a predetermined wave shape that has top portions of portions protruding in a third direction toward the ink discharging surface and bottom portions of portions recessed in a fourth direction opposite to the third direction, the top portions and the bottom portions alternately arranged along the second direction,
• wherein the ink discharging surface includes a usage nozzle disposed area where usage nozzle rows to be used in a printing operation, of the plurality of nozzle rows, are disposed, and
• wherein half a width of the usage nozzle disposed area in the second direction is equal to or less than a distance between adjacent two portions of the top portions and the bottom portions.