Photograph watermarking

Abstract

The protection of information is a very important issue in the digital world where the data can be easily copied, altered and transmitted. One of the well known ways to protect the multimedia is digital watermarking. For a common watermarking system, the test image is processed in digital form. Many researchers have devoted themselves to the studies of extracting watermarks from printed images by scanning. These schemes can resist the print-and-scan process. However, these schemes have some restrictions and weakness when they are applied to the situations of image authentication when images are not easy to be scanned. In this paper, we defined a new image processing manipulation named the print-and-photo (PP) process and proposed a photograph watermarking scheme that can resist it. It is useful especially in some cases when the scanner is not applicable, e.g., a picture on some moving bus. These captured images might be rotated, scaled or chroma distorted after the PP process, and even have perspective and barrel distortions. In our proposed photograph watermarking system, the watermark embedding and extraction procedures are to modify and compare the magnitude order of mean-DCT values in RGB color model. The watermark can be solely extracted from the stego image without the original cover image or any extra information. Further, the QR code is used as the error correction code for strengthening the robustness. Experiment results show that the stego images survive the PP process and the proposed scheme outperforms the related ones.