Block‐based watermarking for color images using visibility of quantization noise

Abstract

AbstractColor images are believed to be more ideal for watermark embedding than grayscale images, because color images provide more space for hiding data. Robustness and transparency of the embedded watermark are required by image watermarking for copyright protection. A feasible solution of taking advantage of color signals in the design for color image watermarking is to effectively exploit the properties of the human visual system. This article proposes a block‐based watermarking scheme that is based on the visibility of quantization noise of the color signal. The block‐based scheme selects perceptually significant portions in the wavelet subband of luminance and chrominance components for robust watermark insertion and embeds the watermark with maximum distortion allowed for transparent watermarking. The strategy is to use the noise detection thresholds of color signals in the color image. By using the noise detection thresholds of wavelet coefficients in the color image, the blocks with high energy can be located and the strength of the watermark can be appropriately determined for watermark embedding. Binary watermark signals are embedded in the coefficients of perceptually significant blocks by quantization index modulation. Simulation results show that the proposed watermarking scheme for color images is robust to malicious attacks while retaining watermark transparency. The performance of the proposed scheme is even better than that of the existing color watermarking method that hides the watermark in the DC components of the DCT domain of color images. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 179–189, 2010