SNR IN and SNR OUT

Hi;

In order to compare the noisy and the De-noised image i should calculate the SNR IN and The SNR OUT

SNR IN :the SNR between the original image I and the noisy In

SNR OUT:the SNR between the De-noised image Id and the original I

For this purpose,I have written a code for calculate the SNR but I'm not sure if it correct because the values i've got they are negatives :/

es=sum(sum(abs(I).^2));

en=sum(sum(abs(In).^2));

SNRIN=10*log10(es/en);

es=sum(sum(abs(I).^2));

en=sum(sum(abs(Id).^2));

SNROUT=10*log10(es/en);