The invention is directed toward improving the efficiency with which an ink-jet printing apparatus performs preliminary discharging of ink. Specifically, the host apparatus of a printer specifies, as part of image data, the timing at which the printer is to execute printhead recovery. The host computer acquires information relating to the nozzle arrangement of the printer and determines, from this nozzle arrangement information and rendered image data, the nozzle number of any nozzle that has failed to discharge ink for more than a predetermined number of scans. When image data is rendered with regard to non-discharging nozzles, preliminary-discharge image data is combined with this data and the combined data is transmitted to the printer.