Watermarking technique based on three-coefficient comparison in DCT domain

Abstract

In order to hide information, Yu et al. (Appl Res Comput 26(3):1082---1083, 1103, 2009) presented a method by using the numerical value relation of three pixel values in spatial domain. Their algorithm is very easy to realize and has a big hiding capacity. But its visual performance is not very good, because it is based on spatial domain and cannot control the modification value effectively in edge region or texture region of image. Our work embedded watermark by comparing the numerical value relation of three neighboring DCT coefficients with Zig-Zag order of block image to enhance the visual performance. First, each block of the host image was transformed by DCT. Then the DCT coefficient matrix was scanned by Zig-Zag scanning order to ensure the continuity of the neighboring coefficients. And then through modifying the numerical value relation of three Zig-Zag neighboring DCT coefficients, the three corresponding watermark bits were embedded in. To further improve its performance, the algorithm also employed redundant encoding, watermark scrambling encryption techniques, etc. The experiments show that the algorithm can guarantee a better quality of watermarked image, and has stronger robust to general image processing operations than the method proposed by Yu et al. (Appl Res Comput 26(3):1082---1083, 1103, 2009).