Robust high dynamic range color image watermarking method based on feature map extraction

In order to protect the copyright of high dynamic range (HDR) images, a novel watermarking method based on feature map extraction is proposed. Since the HDR image provides wide dynamic ranges of visible luminance, the correlations of the three RGB channels are much stronger than those of neighbor pixels. In order to preserve strong relationships of the three color channels, the Tucker decomposition is used to divide the HDR color image along the three color channels so that three feature maps are extracted. The first feature map of the three feature maps is employed to embed watermark for robustness, because it contains most of the energies in the HDR image. The first feature map is divided into non-overlapping blocks, and the Schur decomposition is operated on each block to generate a unitary matrix. Since the texture or edge remains after the tone mapping operation (TMO) of the HDR image, the stable size relation between the pair-wise coefficients in the unitary matrix is established to embed watermark. The experimental results show that the proposed method can efficiently resist different TMOs and common image attacks, outperforming other existing HDR image watermarking methods.