A high embedding capacity image watermarking method with rank-based embedder and decoder

High embedding capacity is desired in digital image watermarking. In this paper, we propose a novel rank-based image watermarking method to achieve high embedding capacity. We first divide the host image into blocks. Then the 2-D discrete cosine transform (DCT) and zigzag scanning is used to construct the coefficient sets with a secret key. After that, the DCT coefficient sets are modified using a rank-based embedding strategy to insert the watermark bits. A buffer is also introduced during the embedding phase to enhance the robustness. At the decoding step, the watermark bits are extracted by checking the ranks of the detection matrices. The proposed method is host signal interference (HSI) free, invariant to amplitude scaling and constant luminance change, and robust against other common signal processing attacks. Experimental results demonstrate the effectiveness of the proposed method.