imnoise(I,'salt & pepper',D)

I don't understand how I know how many pixels are black and how many white ? salt=white ? pepper=black ?

[Adam]

Does it matter which is which for the noise? It's just a boolean, on or off effectively.

Answer 1

[Image Analyst]

Try this to measure what it produced:

numBlackPixels = nnz(grayImage == 0)
numWhitePixels == nnz(grayImage == 255)

Because the help says "J = imnoise(I,'salt & pepper',d) adds salt and pepper noise to the image I, where d is the noise density. This affects approximately d*numel(I) pixels. The default for d is 0.05." then (numBlackPixels + numWhitePixels)/numel(grayImage) should approximately equal the value of d you used. I think it's safe to assume the proportion of black pepper noise and white salt noise should be about the same - 50% of each type.