DCT based multipurpose watermarking technique for image Copyright notification and protection

摘要

A multipurpose image watermarking technique based on DCT is proposed to notify and proteot the Copyright of digital products. In order to achieve this objective, the DCT coefficients of each image block are divided into two parts for embedding the visible and invisible watermark. The visible watermark is embedded in each DC DCT coefficient and most of the A.C DCT coefficients of every block, and the invisible watermark in the rest. Based on the characteristics of Human Visual System ( HVS) , the embedding strength of the visible watermark is varied in accordance with the underlying content of the host image. The invisible watermark is embedded in a quaternity of midrange frequencies. Experimental results show that the visible watermark is hard to re-move and the invisible watermark is robust to common digital signal processing operations.