A Pre-Filtering Method to Improve Watermark Detection Rate in DCT Based Watermarking

In image processing pre-processing is used for preparing or improving performance of operations. In order to improve performance of extraction algorithms in Discrete Cosine Transform (DCT) based watermarking method, a new prefiltering method is proposed in this paper. Enhancement filters are applied to the watermarked image as pre-filtering before running watermark extraction algorithms in DCT based method. These filters are based of mixture of two filters: Unsharp and Laplacian of Gaussian (LoG). Distinction of watermarked part and unwatermarked part is increased by these filters; thus, the watermark information could be extracted with more accuracy. To show the effectiveness of the proposed method, different types of attacks are applied on typical DCT based algorithms. Experimental results show that extracted watermark has better quality than previous method.