1. An image processing apparatus, comprising: an extracting unit to extract digital watermark data from image data; a generating unit to generate a first background-pattern image based on the digital watermark data and a second background-pattern image including identification information for identifying the digital watermark data; and a superimposing unit to superimpose the first background-pattern image and the second background-pattern image on the image data, wherein the identification information is input by accessing a URL attached to the image data.