ML法能够很好的估计信号的信噪比,比较了软阈值，硬阈值及当今各种阈值计算方法,实现了图像的加水印，去噪，加噪声等功能。- ML estimation method can be a good signal to noise ratio, Comparison of soft threshold and hard threshold and today various threshold calculation method, Realize image watermarking, de-nois