A New Image Watermarking Technique in Spatial Domain Using DC Coefficients and Graph Representation

Abstract

In this paper, we propose a new watermarking technique that ensures a suitable compromise between the authentication level of host images and the computational complexity with maintaining a good visual quality of the watermarked image and a good robustness against common image processing attacks. The DC components of host image and image-to-graph representation are used to select particular positions of the original image as inputs of the embedding process in spatial domain. Knowing that the DC value provides a measure of the texture or smooth nature. The proposed model is based on building a directed graph from the original image after dividing it into $N \times N$ blocks. Each block is represented as a vertex and the DC value obtained from Discrete Cosine Transform (DCT) process to the block is used as an edge cost. A simply connected path algorithm is suggested to process the directed graph and to find a simply connected path whose blocks will be used to hide secret data (watermark). One main contribution of this paper is achieving high robustness and low degradation of images in comparison to other existing approaches in spatial domain, by embedding watermark in high textured image blocks. Another main contribution is providing the possibility to recover the watermark even in case of cropping or rotation attacks, due to the embedding of the watermark in several blocks. The proposed model has been tested on gray scale images under several attacks scenario and the experiments results show significant ratios of robustness and bit error rates against the attacks.