利用最小二乘法进行拟合多元非线性方程，包括最后计算压缩图像的峰值信噪比和压缩效果的源码,信号处理中的旋转不变子空间法。- Multivariate least squares fitting method of nonlinear equations, Including the final calculation of the compressed image peak signal to noise ratio and compression of the source, Signal Pr