A feature coding scheme based on the content of JPEG image was proposed. The basic logic of the scheme is to use partial energy relation between groups of 8×8 DCT block to produce related feature code. A semi fragile watermarking scheme combines correctly the content based feature coding with the watermarking scheme. The feature code has the semi fragile property

meaning that it is robust to the acceptable ‘content preserving’ modifications but sensitive to the ‘content changing’ tampering. The lower DCT region is used to form the feature codes while the higher one is used to embed watermarks. The experimental results demonstrate that the proposed algorithm has the advantages such as simple computation complexity

good robustness to JPEG

and precise location of tampered areas.