Application of Unsharp Mask in Augmenting the Quality of Extracted Watermark in Spatial Domain Watermarking

It is generally believed that spatial domain watermarking methods are not robust against common image processing attacks. In this paper, a novel application of an unsharp mask is proposed to increase the performance of watermark recovery in correlation based watermarking. Commonly, unsharp mask is used to improve quality of the image by emphasizing its high frequency contents to enhance the edge and details information in it. Dissimilarity between different parts of image is increased by this filter. Thus, the watermark could recover more correctly from the watermarked image. This filter is applied before running watermark recovery procedure. To show efficiency of proposed filter on the spatial domain watermarking, it is applied on a typical correlation based method. Several experiments are done to evaluate the performance of proposed method is improved by applying this filter before watermark extraction procedure.