An improved SVD-based blind color image watermarking algorithm with mixed modulation incorporated

Abstract

This study systematically investigated the use of singular value decomposition (SVD) for the blind watermarking of color images. The proposed algorithm overcomes most of the problems typically encountered when using existing SVD-based schemes, while concurrently enhancing performance in terms of imperceptibility and robustness. After applying SVD to non-overlapping 4 × 4 image blocks, level shifting is used to control the embedding strength in accordance with the intensity of pixels in each block. The proposed watermark embedding process helps to preserve orthonormality in the unitary matrix and compensate for the resulting distortion. Iterative regulation ensures the accurate retrieval of the embedded watermark, while mixed modulation helps to improve robustness without compromising image quality. Experiment results demonstrate that the proposed watermarking algorithm is highly resistant to a variety of image processing attacks and error-free in the absence of attack. The proposed method outperforms existing SVD-based schemes in terms of imperceptibility and robustness at a payload capacity of 1/16 bit per pixel.