说明：  实现直接序列扩频水印的嵌入与提取。基于待嵌入消息生成二进制水印序列,生成扩频码，用消息序列调制生成水印序列。依次处理灰度图像的每一个载体图像像素，根据相应位置 水印序列完成嵌入修改。
(Realize the embedding and extraction of direct sequence spread spectrum watermark. The binary watermark sequence is generated based on the message to be embedded, the spread spectrum code is generated, and the watermark sequence is generated by message sequence modulation. Each carrier image pixel of gray image is processed in turn, and the embedding modification is completed according to the corresponding position watermark sequence.)