how to calculate actual snr of image in matlab?
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vipul utsav
am 4 Dez. 2012
Kommentiert: Alan Keenan
am 20 Sep. 2021
how to calculate actual snr of image in matlab?
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Image Analyst
am 4 Dez. 2012
Get the signal - that's your "true" noiseless image.
Get the noise - that's your actual noisy image minus the "true" noiseless image.
Divide them element by element, then take the mean over the whole image.
12 Kommentare
Image Analyst
am 5 Dez. 2012
Well, what if your signal is 100 everywhere, and your noisy image is 100 plus or minus 100, so it goes from 0 to 200. Don't you agree that that is a very very noisy image and it should have a low signal to noise ratio? It's total noise - all over the place. But it's mean is still 100 - same as your signal. So just looking at the means, you can't tell the difference between your perfect noise-free signal and the incredibly noisy signal. How is that any good?
By the way, you can always omit pixels where the noise is zero if you want.
Weitere Antworten (1)
Dhurgham Al-karawi
am 29 Aug. 2017
Bearbeitet: Image Analyst
am 29 Aug. 2017
Hi,
Here you are.
img=imread('.JPG');
img=double(img(:));
ima=max(img(:));
imi=min(img(:));
ims=std(img(:));
snr=10*log((ima-imi)./ims);
4 Kommentare
Image Analyst
am 17 Okt. 2019
A signal to noise ratio requires both a signal, and noise. If you don't have each of those, you can't do it. However there are single image quality metrics. Try this link.
Alan Keenan
am 20 Sep. 2021
Perform a histogram on your image and then decide at what level you consider to be signal, i.e., above a value is signal and below that value is noise. If your image is in dB then you might use -6dB as the threshold value. In my case my max signal value is always 0dB as it has been normalised to the max value and converted to dB. So you can say anything less than -6dB is noise and anything greater than -6dB is signal. An easy way to calculate the noise floor is rms(rms(image));. This means that if your signal has a max value of 0dB then the peak SNR for your signal = 0dB + the value of the rms calculation.
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