Hybrid method for image watermarking

Geometric and signal processing attacks are the major challenge of the digital watermarking methods. It is troublesome to retrieve the cover image in the decoding section when it has undergone several attacks. This method provides good robustness against different attacks and to retrieve the original image. In the embedding section the original image undergoes Gaussian filtering and the low frequency component is extracted. A secret key is used to arbitrarily select grey levels to embed the watermark. The histogram of the filtered image with regard to these chosen gray levels is constructed. The watermark is embedded only to selected pixel values based on the available secret key. Huffman and arithmetic encoding is performed to the high frequency component of the image. A secure band is constructed between the selected and the non-selected pixel groups. High frequency component modification enhances the effectiveness of the watermarking scheme. In the decoding part the groups to which the embedded data is found out using the secret key. The cover image is retrieved by doing the reverse operation carried in the encoding section. The data hidden using this method is highly secure and the cover image can be retrieved.