Block-By-Block SVD Image Watermarking with Variable Block Sizes

This paper presents a block-by-block SVD watermarking algorithm with variable block sizes. The paper makes a comparison between the traditional method of Liu and the proposed method. In the proposed approach, the original image is divided into blocks, and then the watermark is embedded in the singular values (SVs) of each block, separately. This segmentation and watermarking on a block-by-block basis makes the watermark more robust to the attacks such as noise, compression, cropping and other attacks as the results reveal. Watermark detection is implemented by extracting the watermark from the SVs of the watermarked blocks.  Extracting the watermark from one block at least is enough to ensure the existence of the watermark. Experimental results show that the proposed method with different block sizes is superior to the traditional method of Liu for embedding unencrypted watermarks.