Digital image watermarking for printed and scanned documents
Kharittha Thongkor, Thumrongrat Amornraksa · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2017
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.