Chaos System and YCbCr Color Space Based Semi-Fragile Watermarking Algorithm for Color Images

For identifying the content integrity of color images, a semi-fragile watermarking algorithm is proposed. First, the color image was converted from RGB color space to YCbCr color space, then the watermark was obtained by iterating the chaos system from the initial value which depends on a grayscale image, a watermarking key and the low coefficients of Y component. According to the invariant properties of discrete cosine transform (DCT) coefficients before and after joint photographic experts group (JPEG) compression, the watermark was embedded into the intermediate-frequency DCT coefficients of Y component. Experimental results show that the proposed algorithm is not only robust against JPEG lossy compression, with zero false alarm ratio when quality factor (QF) of JPEG compression is higher than 40, but also sensitive to tampers with a detection ratio above 0.9.