Color image blind watermarking scheme based on QR decomposition

• The original watermark is 24-bit true-color image.
• The proposed method belongs to blind detection.
• The color image watermark is embedded into the first row fourth column element in the matrix R obtained by QR decomposition.
• The proposed method is highly robust.
• Without knowing the correct keys no attacker can extract the correct data.

Most of the existing color image watermarking schemes use binary or gray-level image as watermark, and many of them belong to non-blind watermarking methods. It is a challenging problem to design a blind color image watermarking scheme. Based on QR decomposition, this paper proposes a novel blind image watermarking scheme to embed color watermark image into color host image, which is different from some existing works using the binary or gray-level image as watermark. Firstly, the color host image is divided to 4×4 non-overlapping pixel blocks. Then, each selected pixel block is decomposed by QR decomposition and the first row fourth column element in the matrix R is quantified for embedding the watermark information. In the extraction procedure, the watermark can be extracted from the watermarked image without the requirement of the original host image or the original watermark image. Experimental results, compared with the related existing methods, show that the proposed color image scheme has stronger robustness against most common attacks such as image compression, filtering, cropping, noise adding, blurring, scaling and sharpening etc.