中文说明：代码利用DWT算法实现了电子水印技术。 其中包括了水印的插入，提取，以及4种不同的攻击。最后，测量了psnr
English Description：
The code uses DWT algorithm to realize the electronic watermarking technology. It includes the watermark insertion, extraction, and four different attacks. Finally, the PSNR is measured