How can I calculate the PSNR of two images in matlab? The images are obtained as intermediate results. How can I use these images to calculate the PSNR value

How can I calculate the PSNR of two images in matlab? The images are obtained as intermediate results. How can I use these images to calculate the PSNR value

[D Joseph]

Can PSNR have negative values

Answer 1

[Walter Roberson]

http://www.mathworks.com/help/images/ref/psnr.html

Yes, PSNR can be negative. It is 10 * log10() of a ratio, so if the ratio is less than 1 then log10() is negative and so the PSNR would be negative.

[D Joseph]

psnr = 10*log10(255*255/mean2((nI-I).^2))

Can this be used in matlab to calculate PSNR value. How can I plot a graph using this PSNR value of several images?

[Walter Roberson]

nI and I would have to be double() for that to work -- or rather, they could not be uint8() or any other unsigned class.

I = double(YourImage);
for K = 1 : 20
  nI = I + randn(size(I)) * 1.2345*K;
  ps(K) = 10*log10(255*255/mean2((nI-I).^2));
end
plot(ps);

[D Joseph]

Thanks@Roberson