Method for the marking of documents
AssigneeEcole Polytechnique Federale de Lausanne
InventorsMurat Kunt, Joseph Bigun, Benoit Duc
Life of this patent
Estimating the term…
Abstract
A mark is incorporated to the original during the fabrication of said original in such a way that said mark is invisible on the original but appears on the copy of the original which is made by using a photocopying machinge. The mark is incorporated by additionally mixing the original image to be protected and the marking image to be concealed in the original by modulating one or the other of the images or by manipulation of Fourier transforms.
Claims11
A method for the marking of documents, said documents consisting in digitized images of black and white, grey and/or colour types, wherein a digitized mark image is intimately mixed together with the original digitized image by means of a digital operation producing a modified digital image which occupies the same portion of surface as the original image, each grey or colour value in the modified digital image being expressed as a function of the grey or colour values of the original image and of the mark image, in such a way that the mark is not noticeable in the modified image to the human eye but appears on the copy of this original document produced by means of a photocopier, the digitalization of the original document being effected with a sampling pitch at least twice finer than that of the photocopier.
Dependencies are inferred from the claim text.