Calculate SNR in single image in MATLAB

Question

I have this image:

I want to calculate SNR in it. For this i used code:

img=imread('noicy.JPG');
img=double(img(:));
ima=max(img(:));
imi=min(img(:));
ims=std(img(:));
snr=20*log10((ima-imi)./ims)

Is that correct code to calculate SNR?

Answer 1

The definition of SNR can be found here or here :

Both the standard and the industry definition can be used ( 10log(x) and 20log(x) ). check this

now, the signal is equal to the mean of the pixel values ( mean(img(:)) ) and the noise is the standard deviation or error value of the pixel values ( std(img(:)) ).

You may use either the ratio or the SNR=10*log10(signal/noise) to express the result in decibel.