Firstly,block edges is extracted directly from compressed domain without decompressing.Secondly,network flow based ratio contour algorithm is used to extract salient closed boundary.

• 从压缩域直接提取块边缘,使用基于网络流理论的比率轮廓算法从块边缘图像中提取显著闭合边界,用傅立叶描述子刻画显著闭合边界,进行图像检索。