1. An image processing system comprising: an integrated circuit configured to receive image data, generate identification information of a pixel of interest of the received image data, access density conversion information from among a plurality of pieces of the density conversion information, the density conversion information being based on one of a plurality of image processing methods, in which the identification information is associated with the density conversion information, and convert a density of the pixel of interest to a density corresponding to the identification information by using only the identification information, or maintain the density of the pixel of interest unchanged when the density of the pixel of interest is not converted; and a processor communicatively coupled to a memory, the processor being configured to update the density conversion information in response to a newly selected image processing method, the updated density conversion information being associated with the newly selected image processing method.