1. An image processing apparatus comprising: a print control unit configured to cause a printing apparatus to print, on a sheet, an image stored in a memory, such that the image is printed on the sheet with a density lower than a predetermined density value; an acquiring unit configured to acquire a read image obtained by reading, by a reading apparatus, the sheet corresponding to the image printed by the print control unit on the sheet; an extracting unit configured to extract information that is added by a user on the image printed by the print control unit on the sheet, from the read image acquired by the acquiring unit, based on the read image; and a combining unit configured to combine the image stored in the memory and the information extracted by the extracting unit, wherein the extracting unit specifies the information having a density higher than a predetermined density value from the read image, according to a level of each of a plurality of color components included in the read image, and extracts the specified information from the read image.