1. A method, comprising: generating image data that provides a digital representation of an original image; providing an encoding transformation function for positioning pixels of a substantially invisible representation of said original image inside said original image, wherein the encoding transformation function scrambles coordinates for the substantially invisible representation of said original image based on coordinates of the original image; printing said original image on an output copy sheet; and printing said substantially invisible representation of said original image on said output copy sheet, with said pixels of said substantially invisible representation of said original image dispersed among said original image according to said encoding transformation function.