function PSNR = psnr(f1, f2)
%计算两幅图像的峰值信噪比
k = 8; %k为图像是表示地个像素点所用的二进制位数，即位深。
fmax = 2.^k - 1;
a = fmax.^2;
e = double(f1) - double(f2);
[m, n] = size(e);
b = sum(e(
.^2);
PSNR = 10*log(m*n*a/b);
function ERMS = erms(f1, f2)
%计算f1和f2均方根误差
e = double(f1) - double(f2);
[m, n] = size(e);
ERMS = sqrt(sum(e(
.^2)/(m*n));