Block based digital watermarking using singular value decomposition on color images

In this paper block based digital color image watermarking scheme is proposed using singular value decomposition (SVD). Dividing an image into block gives more space to embed multiple watermarks which in turn gives a more secure watermarking technique. In the proposed approach, the host color image is divided into R, G, B channels. Each channel is further divided into four blocks, and then four watermark images are embedded in each of these channels. Thus one can hide multiple watermarks in the host image. This segmentation and watermarking process makes the watermark tamper resistant. Study also shows that by dividing the host image into blocks of variable sizes one can hide different sizes of watermarks. This technique works well for both square and rectangular images. Robustness tests show that despite high capacity of watermark it can withstand many common attacks and image modification successfully.