US Patent 7876473 Apparatus and method for information burying

A dot pattern including a set of plural dots arranged substantially periodically is formed. When positions of the plural dots are shifted dot by dot, a combination of an amount and a direction of shift of dot positions to be shifted is changed. A pattern obtained by repeating, for each predetermined period, a pattern processed in this way is superimposed on an image. Sizes of the respective dots are the same and only dot positions of the dots are shifted. Therefore, plural dot patterns having different amounts and directions of shift of dot positions visually look like uniform patterns and a sense of hindrance is low.