PSNR

https://www.mathworks.com/help/vision/ref/psnr.html

PSNR = 10 * log10( R^2 / MSE)

MSE = Sum [ ( I1 - I2) ^ 2 ] / (M*N)

For image in range 0-1,  R = 1
For image in range 0-255, R = 255