1. A secure identification document comprising a printed identification image and a printed security pattern image, the security pattern image being inserted into and simultaneously printed in one step with said identification image, each image being defined by a plurality of pixels, the characteristic level of each pixel i of the security pattern image being linked, by a function F, to a matrix Ωi of pixels defined in the identification image, said pixels of the matrix Ωi surrounding the location i of a pixel of the security pattern image to insert, said function F taking into account the characteristic level G(Ωi) of the pixels within the matrix Ωi and the texture level T(Ωi) of said matrix Ωi.