Digital Image Watermarking Based On DWT-DCT

The development of the internet has greatly contributed to the wide use of digital media like images, audio, video. The image can be duplicated unlimitedly without any quality loss and can also be easily distributed and soaked. This presents problems compromise digital image security. Little by little peoples are motivated to embed information such as some information or even secret message in the digital image for value-added functionalities and possibly secret communication. A new emerging technology, digital watermarking, protects digital media by embedding a robust signal directly into the media, thus providing a promising way to protect the digital media from manipulation and illicit copying.In this thesis the frequency-domain watermarking is presented. The blind, imperceptible and robust combined DWT-DCT algorithm is proposed to embed some information (watermark) in the digital cover image and to recover the watermark or hidden message. The watermark method is done using a combination of the Discrete Wavelet Transform (DWT) and the Discrete Cosine Transform (DCT). We also use the Peak Signal-to-Noise (PSNR) to evaluate the image quality. The watermarking method combines and adapts various aspects from existing watermarking methods. Experimental results show that the presented method to embed watermark is robust against various signal processing and compression attacks like JPEG compression, Noise addition, Geometrical Rotation and Cropping. The imperceptibility of watermarked image is also showing according to the human visual system.