在数字图像处理中，运用MATLAB中的函数compare可以用来计算图像压缩前后的误差和直方图-In digital image processing using MATLAB functions compare the error and histogram can be used to calculate the image before and after compression

Image watermark using 3 level DWT, compare with 1, 2 level

通过小波技术对一维信号进行分解与重构，比较变换前后的图像，获取有用的信息(Wavelet technology is used to decompose and reconstruct one dimension signal, compare the image before and after the transformation, and obtain useful information)