1. An image processing device comprising: a processor; and a memory storing computer-readable instructions therein, the computer-readable instructions, when executed by the processor, causing the image processing device to perform: acquiring a calibration value based on a plurality of test images that are printed on a recording medium, the calibration value indicating an amount of calibration; calibrating a target value by using the calibration value, the target value being used to determine a dot formation state of each pixel of an image in a halftone process; and generating print data by performing the halftone process on each pixel using the calibrated target value.