AWGN for a grayscale image
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Hello everyone,
I need to add AWGN to a grayscale image for the purpose of denoising. Till now I was using "imnoise" to add the gaussian noise but somewhere I doubt or I am confused whether I am adding correct noise or not.
Is this the correct method to add AWGN in an image? If not, please tell me how to add this kind of noise.
Thanking you in advance
Vivek Singh Bhadouria
India
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Rick Rosson
le 31 Août 2011
Yes, imnoise is the right function to use.
Why are you concerned that it might not be the correct function to use?
Rick
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Wayne King
le 22 Sep 2011
Hi, The answer is both.
The Gaussian noise is additive if you use the 'Gaussian' option.
J = imnoise(I,'gaussian',M,V)
The Gaussian noise is multiplicative if you use 'speckle'
J = imnoise(I,'speckle',V)
Hope that helps, Wayne
4 commentaires
Wayne King
le 27 Sep 2011
Sorry Vivek, you're right. I misread the help. The multiplicative option does use rand()
Image Analyst
le 27 Sep 2011
I'm not sure why they call it "speckle." At least it appears to have nothing to do with speckle in the laser imaging sense. My textbook on statistical optics says "Under the assumptions of the given statistical model, the speckle intensity follows a negative exponential law, and speckle phase follows a uniform law." The law (equation) it gives for laser speckle intensity distribution is p(i) = sigma^(-2) * exp(-i / sigma^2). This is definitely different than you'd get from MATLAB which says "adds multiplicative noise to the image I, using the equation J = I+n*I, where n is uniformly distributed random noise with mean 0 and variance v." So MATLAB's speckle noise is not laser speckle noise - it uses some other definition of speckle.
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