patent application date 23.6.26
name digital watermark embedding and extracting method based on remainder image
publication (announcement) number CN147119
publication (announcement) date 24.1.28
category physics < (patent right) Jiang Lingge, inventor (designer) of Shanghai Jiaotong University
Address 23 No.1954 Huashan Road, Shanghai; Wang Dongjian; He Chen; Feng Guorui
International Application
International Publication
Date of Entry into China
Patent Agency Shanghai Jiaoda Patent Office
Agent Mao Cuiying
Abstract
A digital watermark embedding and extracting method based on residue image, which divides the image into blocks in the spatial domain and uses chaotic mapping to scramble each virtual block. The carrier image data in each virtual space is decomposed into "remainder image block" and "quotient image block". The watermark information is encrypted by chaotic sequence and spread by direct sequence, and the spread watermark information is embedded in the "remainder image block". After processing the out-of-bounds data, each "remainder image block" and the corresponding "quotient image block" are assembled, and the block is scrambled by chaotic mapping, and the watermarked image is obtained after each block is assembled. When extracting the watermark, the image is divided into blocks according to the sequence when the watermark is embedded, and the corresponding "residual image block" is obtained by chaos, and then the "residual image block" is demodulated by the detection sequence generated by chaotic mapping, and the threshold judgment is made. The obtained encrypted watermark is decrypted by chaotic mapping, and the hidden watermark information is recovered.
sovereignty term
1. A digital watermark embedding and extracting method based on a residue image, which is characterized by comprising the following specific steps: 1) obtaining chaotic mapping parameters and initial values according to an authorized system key, and generating three groups of chaotic random sequences, which are sequentially denoted as PN1, PN2 and PN3, wherein the lengths of the sequences PN1 and PN3 are equal to the pixel number M1×M2 of the carrier image, and the length of the sequence PN2 is equal to the bit number W of the watermark data. 2) image block scrambling, encryption and spread spectrum of watermark data: divide the M1×M2 pixels of the carrier image into imaginary numbers as many as the number of watermark bits w, each block size is N1×N2 pixels, arrange the sequence PN1 into M1×M2 matrix consistent with the shape of the carrier image, and decompose it into imaginary numbers with the size of N1×N2, and expand the element values with the coordinate of (i, j) in the block into log2 (N1. Log2(N1) and log2(N2) are taken in turn to form a coordinate pair (cx(i), cy(j)), and the pixels at (I, j) and (cx(i), cy(j)) in each image block are interchanged in turn to realize the built-in scrambling of the carrier image block, and the chaotic sequence PN2 is quantized into /1. The chaotic sequence PN3 is quantized into a pseudo-random sequence with zero mean value as a spread spectrum modulation sequence, and the encrypted watermark bits are mapped from {,1} to {-1, +1}, and the quantized random sequence PN3 is used for direct sequence spread spectrum to obtain spread spectrum watermark information; 3) digital watermark embedding: each scrambled carrier image block is embedded with a watermark bit, and each small block is decomposed into a "remainder image block" and a "quotient image block" by modulo m1, and the encrypted and spread-spectrum watermark is multiplied by the watermark intensity and added to the corresponding "remainder image block", and the value exceeding [, m1-1] is corrected by modulo m1, so that the "remainder image block" and the corresponding. 4) Watermark extraction: according to the authorization key, the received watermarked image is scrambled in blocks in the same way as the embedding stage by using chaotic mapping, the corresponding "remainder image block" is obtained by selecting modulus m2 according to the channel condition, the spread spectrum modulation sequence is recovered according to the key as the detection sequence of the receiver, and the detection sequence is used for correlation operation and judgment with each "remainder image block" to obtain encrypted watermark data; Finally, according to the key, a decryption sequence is generated by chaotic mapping, and the watermark information is decrypted to get the embedded watermark information. The selection of modulus m2 can be divided into two cases: m2 = m1 when the carrier image is not polluted in the publishing process, otherwise m2 is 256.