1. An image recording apparatus comprising: a recording nozzle group capable of discharging three or more types of ink; a driving means for moving the recording nozzle group relatively with respect to a recording medium; an image brightness signal inputting means for inputting three or more types of image brightness signals; and a recording and controlling means for recording an image onto the recording medium by causing the three or more types of monochrome ink to be discharged from the recording nozzle group based on the image brightness signals that are input by the image brightness signal input means.