A Semi-fragile Blind Watermarking Scheme for Color Images Based on Visual Cryptography and Discrete Cosine Transform

This paper presents a semi-fragile blind watermarking scheme for color images based on Visual Cryptography (VC) and Discrete Cosine Transform (DCT). Firstly, the binary watermark image is separated into two shares, i.e., the public share and the private share, by using the VC technique. Then, the color host image is converted from the RGB color space into the HSV color space. Next, the DCT transform is performed on each 8 × 8 block in the V component of the host image. Finally, the public share is embedded into the DCT middle frequency coefficients. During the extraction process, the public share is first extracted, and then it is stacked over the private share to recover the original watermark. The experimental results show that the proposed scheme has good invisibility and good robustness to color transform, cropping and JPEG compression operations, but is vulnerable to Gaussian noise, Poisson noise, Speckle noise and Gaussian low-pass filtering attacks.