A calculator calculates a total value of tone values of all pixels in each aggregation by allocating each pixel of M-valued image data to one aggregation. Each block is either one of ejection-port groups including ejection ports having a common liquid channel serving as a liquid supply source or one of divided ejection-port groups. Each aggregation includes pixels of the M-valued image data corresponding to dots formed on a medium when liquid is ejected from ejection ports in one block during one L ejection period. Each L ejection period is obtained by dividing, by a plural number, a number of ejection cycles required to record an image on one recording medium. A tone-value reducer reduces tone values of at least part of pixels in an adjustment-requiring aggregation so that the total value becomes less than a threshold. A transmitter transmits the adjusted M-valued image data to a liquid ejecting device.