A printing system for inkjet printing on a medium, the printing system comprising: an image processing unit configured to perform image processing on an input image that is an image to be printed, the image processing unit generating, as a generated image, an image in which a gradation number of pixel values is smaller than that of the input image; and a printing unit configured to execute printing on the medium based on the generated image generated by the image processing unit; wherein the printing unit includes an inkjet head configured to eject ink onto the medium, the inkjet head forming ink dots on the medium by ejecting ink to positions set on the medium in correspondence with the pixels in the generated image; the image processing unit is configured to generate the generated image by performing quantization processing for performing quantization by comparing a pixel value of each pixel in the input image with a preset threshold; characterized in that the image processing unit is further configured: in the quantization processing, to calculate a dot influence value, which is a value indicating to what extent the position corresponding to a selected pixel, which is a pixel of the input image selected as a target of quantization, is covered by ink dots formed at positions set on the medium in correspondence with peripheral pixels that are peripheral to the selected pixel, the dot influence value being calculated based on a dot model, which is data obtained by modeling a relationship between a size of the ink dot and a printing resolution, to perform an adjustment that reflects the dot influence value on at least one of the pixel value of the selected pixel or the value of the threshold, and then to compare the pixel value with the threshold. an image processing unit configured to perform image processing on an input image that is an image to be printed, the image processing unit generating, as a generated image, an image in which a gradation number of pixel values is smaller than that of the input image; and a printing unit configured to execute printing on the medium based on the generated image generated by the image processing unit; wherein the printing unit includes an inkjet head configured to eject ink onto the medium, the inkjet head forming ink dots on the medium by ejecting ink to positions set on the medium in correspondence with the pixels in the generated image; the image processing unit is configured to generate the generated image by performing quantization processing for performing quantization by comparing a pixel value of each pixel in the input image with a preset threshold; in the quantization processing, to calculate a dot influence value, which is a value indicating to what extent the position corresponding to a selected pixel, which is a pixel of the input image selected as a target of quantization, is covered by ink dots formed at positions set on the medium in correspondence with peripheral pixels that are peripheral to the selected pixel, the dot influence value being calculated based on a dot model, which is data obtained by modeling a relationship between a size of the ink dot and a printing resolution, to perform an adjustment that reflects the dot influence value on at least one of the pixel value of the selected pixel or the value of the threshold, and then to compare the pixel value with the threshold.