实现pdf文件上的签名水印,不错的程序代码-Implement the signature on the PDF file watermark, a good program code

利用最小二乘法进行拟合多元非线性方程，ofdm系统仿真 含16qam调制 fft 加窗 加cp等模块，实现了图像的加水印，去噪，加噪声等功能。- Multivariate least squares fitting method of nonlinear equations, ofdm system simulation including 16qam modulation fft windowing modules plus cp, Realize image watermarking, de