additive Gaussian noise with different SNR

edit

first of all, GaussianBlur is the wrong one, (it reduces noise by interpolating).

also i'd guess, that you don't 'calculate' the SNR, but set it to a couple of fixed values, like: we'going to test with 10%, 20%, 50%, 80% noise.

you could do this with cv::randn(), and 'a' would be 0, and 'b' would be the std-dev calculated according to the desired SNR. ( for a SNR of 90 (10% noise), you want 255 * 10/100 for b.)

let's just try it on lena:

Mat im = imread("lena.jpg", 0);
Mat noise = Mat(im.size(), CV_8U);
Scalar a(0);
Scalar b(20) ;
randn(noise,a,b);
imshow("noise",noise);
imshow("add",im + noise);
waitKey();