An improved color image watermarking algorithm based on QR decomposition

Most of the existing color image watermarking schemes use binary or grayscale image as watermark, and many of them belong to non-blind watermarking methods. In this paper, an improved color image watermarking algorithm based on QR decomposition is proposed to embed color watermark image into color host image. For embedding watermark, the 24-bits color host image is divided into non-overlapping 3 x 3 pixel blocks and each pixel block is decomposed by QR decomposition, and the 24-bits color watermark image is embedded into the color host image by modifying the relation between the second row first column coefficient and the third row first column coefficient of the orthogonal matrix Q. For extracting watermark, only the watermarked image is needed. Experimental results show that the proposed color image scheme not only has better watermark performance such as invisibility, robustness, security, capacity, and computation complexity, but also overcomes the false-positive detection problem.