In a case where a line drawing, such as a thin line, is included within input image data, the output of a non-ejectable nozzle is compensated for while suppressing deterioration of reproducibility thereof. Based on positional information for specifying an abnormal nozzle in which an ejection failure has occurred among a plurality of nozzles arrayed in a nozzle column, a pixel value of a pixel on a pixel line corresponding to the abnormal nozzle and a pixel value of a pixel on a pixel line corresponding to another nozzle that is located in close proximity to the abnormal nozzle and in which no ejection failure has occurred are exchanged for the input image data. Then, halftone image data is generated by performing halftone processing for the input image data for which pixel value exchange has been performed.