1. A non-transitory computer readable storage medium storing a set of program instructions installed on and executed by a computer, the program instructions, when executed, cause the computer to perform a method comprising: determining a single offset value based on a plurality of offsets of measurement values acquired from a plurality of test images printed with a first color; 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, wherein acquiring the calibration value includes determining a single calibration value for the first color corresponding to the single offset value; calibrating, by using the calibration value, a conversion correlation between each of a plurality of input values and each of a plurality of output values, the calibrated conversion correlation being a conversion correlation between each of the plurality of input values and each of a plurality of calibrated output values, the plurality of input values including a part of the plurality of input values which is greater than a predetermined input value, the part of the plurality of input values corresponding to a part of the plurality of calibrated output values which is set to a maximum value; performing a color conversion on the image data by using the calibrated conversion correlation; and generating print data by performing a halftone process on the converted image data through the color conversion, wherein the print data is printed by a colorant representing the first color.