中文说明：两个图像质量评价函数，psnr峰值信噪比，正则均方误差nmse，能可用于去噪图像和压缩图像的质量评价，很有用啊。
English Description：
Two image quality evaluation function, PSNR peak signal-to-noise ratio, regular mean square error NMSE, can be used for denoising image and compressed image quality evaluation, very useful ah.