基于扩展频谱通信技术，对宿主图像的频域进行2维DCT变换，采用保持图像亮度的JND（just noticeable distortion）门限值和多数字基底对宿主图像DCT频域进行选块，对中频分量的DCT交流系数分组嵌入水印比特，以随机二值序列对高低频分量的DCT系数的水印比特嵌入进行控制，使多个数字盲水印信号载波传输于混叠的DCT频带。该算法可预估水印嵌入量，提取水印无需宿主图像和水印图像，仿真测试实例表明，该算法能有效抵抗滤波、加噪、剪切、JPEG有损压缩，具有较强的顽健性和鲁棒性。

Based on spread spectrum communications,the approach concerns mainly a series of techniques: the substitution of DCT of 2D in frequency domain of the owner image,the use of selection-and-group tactics conducted by means of JND threshold of gray-image and the multiple-based work underlying DCT frequency domain of the owner image,the classification of embedded watermarking with AC of intermediate frequency,the performance at random on AC of high-low frequency that embedded,and the realization of digital blind watermarking of multiple gray watermarking in order to transmit it by the mode of carrier wave.This algorithm evaluates the capacity of the digital watermarking and extracts the digital watermarking without the original watermark and the owner image.The experimental results proves that the algorithm is of good robustness and renitency for the procedures,like filtering,adding noise,clipping,JPEG compression.