calculate noise standard deviation from original image and smooth image

Lets say, I have 2 images. The first one is the original noisy image and the 2nd one the denoised image. Now using the 2nd denoised image, how can I estimate the noise std. deviation for the first image?

[Noud Hospers]

Good question! So you now have two image's and the difference between them is noise. So you for simplicity you want to end up with a data matrix with just the noise and determine the std over this matrix. So to get to this matrix you should subtract the image WITH noise from the image WITHOUT noise. This would look like this in Matlab!

#Convert .fig file to NxN Matrix

Noisy_Image=convert_image(Noisy Image file) ;

Denoised_Image=convert_image(Denoised Image file) ;

#Get noise matrix from image matrices

Image_Noise=Noisy_Image - Denoised_Image;

#Get std from noise matrix

Noise_std=std(Image_Noise);