Robustness Comparison of Color Image Watermarking Schemes in Uniform and Non-uniform Color Spaces

Watermarking technique is to hide a sequence of random numbers or a recognizable binary pattern, or the so-called digital watermark, into the media for authorized uses. Color image watermarking even plays an important role due to distributed, manipulated and forged behaviors over networks. In this paper, robustness comparison of color image watermarking schemes using different color spaces for embedding is undertaken. The color watermarking scheme implemented in this paper is to select the signal with high perceptual redundancy for transparent watermark embedding in the wavelet domain. Binary watermark signals are repeatedly embedded into the selected wavelet coefficients by the way of quantization index modification. The watermarking scheme utilizing perceptually redundant signal spaces in both uniform and non-uniform color spaces for hiding watermarks are conducted to compare the corresponding robustness of the embedded watermark. Experimental results of the comparison show that the non-uniform color space can provide a certain part of color signals a large amount of perceptual redundancy for hiding high-strength watermark signals. The watermark embedded in the non-uniform space is always robust than that embedded in the uniform space. Key words: Color image watermarking, perceptual redundancy, uniform color space, non-uniform color space