Embedding information into images by varying pixel parameters

摘要

An image forming apparatus which comprises image inputter for inputting an image, information inputter for inputting information to be added to the image, image producer for producing an output pixel corresponding to the image inputted by the image inputter using a line screen whose line width is changed depending on desired density of the output pixel, position changer for changing a position of the output pixel to be produced in accordance with the information inputted by the information inputter in a line width direction of the line screen within the width of the screen in a process of producing the output pixel corresponding to the inputted image by the image producer, and controller for controlling the image producer to produce the output pixel in the position changed by the position changer using the line screen.