High-capacity colour image watermarking using multi-dimensional Fourier transforms and semi-random LDPC codes

In this paper, we propose a colour image watermarking scheme based on the Spatio-Chromatic Fourier Transform (SCFT) with spread-spectrum signaling enhanced by error correction using semi-random low density parity check (SRLDPC) codes. The SCFT transform enables efficient use of the embedding properties of the complex Fourier representations without incurring additional computational complexity. The watermark detection is based on a statistical maximum likelihood approach using a Weibull distribution known to be well-suited for modelling the SCFT coefficients. The proposed embedding scheme is image-adaptive, and provides control over the watermark embedding strength according to the local properties of the SCFT representation of the host image. The efficiency and data hiding capacity of the proposed watermark embedding scheme are found to be greatly enhanced by the use of SR-LDPC codes. Simulation results and comparisons with colour-component Discrete Fourier Transform (DFT)-based schemes demonstrate the increased robustness of the proposed LDPC-coded, colour image watermarking algorithm against standard attacks including additive white Gaussian noise and JPEG compression.