We present a spatial domain image watermarking for printed and scanned documents. In the watermark embedding process, a watermark image is embedded into the blue color component of a white color image. The result is overlaid with information, and printed out on a piece of paper. In the watermark extraction process, a printed document is first scanned back to obtain an electronic copy. Geometric distortions from the printing and scanning processes are then reduced by an image registration technique based on affine transformation. All watermarked components are used to determine a threshold for watermark bits extraction. The performance of the proposed watermarking method was investigated based on different scanning resolutions, printing quality modes, and printable materials. Watermark extraction from ripped, crumpled, and wet documents was also investigated. The promising results demonstrate the effectiveness of the proposed method.
This paper proposes a new watermarking scheme for color images, in which all pixels of the image are used for embedding watermark bits in order to achieve the highest amount of embedding. For watermark embedding, the S component in the hue-saturation-value (HSV) color space is used to carry the watermark bits, while the V component is used in accordance with a human visual system model to determine the proper watermark strength. In the proposed scheme, the number of watermark bits equals the number of pixels in the host image. Watermark extraction is accomplished blindly based on the use of a 3×3 spatial domain Wiener filter. The efficiency of our proposed image watermarking scheme depends mainly on the accuracy of the estimate of the original S component. The experimental results show that the performance of the proposed scheme, under no attacks and against various types of attacks, was superior to the previous existing watermarking schemes.