Block Based Color Image Watermarking Scheme Using QSVD

In this paper, we first introduce a new tool for color image decomposition based on quaternion representation of a colour image and quaternion matrix algebra. To perform the decomposition of such an image, we introduce the singular value decomposition of a quaternion matrix. Based on this mathematical technique of quaternion singular value decomposition (QSVD) this paper presents a block based digital colour image watermarking scheme. In the proposed approach, the original colour image is divided into blocks, and then the watermark is embedded in the singular values of each block separately. This segmentation and watermarking process makes the watermark much more robust to many image attacks like rotation, scaling, noise, compression, cropping, and lowpass filtering Watermark detection is implemented by extracting the watermark from the singular values of the watermarked blocks. Experimental results show that extracting the watermark from one block at least is enough to ensure the existence of the watermark.