Disclosed are an image processing device, a printing apparatus, an image processing method, and a program capable of making processing common among printing modes to simplify an entire image processing flow in image processing based on a plurality of printing modes with different definition. An image processing unit 14 includes an image size adjustment unit 20 which adjusts the size of an input image, and a halftone processing unit 24 which performs halftone processing on the input image size-adjusted by the image size adjustment unit 20 to generate a halftone image. The image size adjustment unit 20 adjusts the input image to the same size in two or more printing modes among a plurality of printing modes with different definition, and the input image of the same size is subjected to halftone processing in the halftone processing unit 24.
