Adding high density salt and pepper noise to an image

I am taking 'cameraman.tif' as my input image.

How can I add high density salt and pepper noise to it so that if I place 3X3 window over it and scan for uncorrupted pixels in it the uncorrupted pixels will come out to be 3?

Please provide matlab code for this

[Roaa Mohammed]

clc; img = imread('cameraman.tif'); na = imnoise(img,'salt & pepper',0.02); black=3; white=253; nb = img; Rmatrix = randint(size(img,1),size(img,2),[0,255]); nb(Rmatrix <= black) = 0; nb(Rmatrix >= white) = 255; subplot 131;imshow(img),title('ORIGINAL IMAGE'); subplot 132;imshow(na),title('NOISE USING FUNCTION'); subplot 133;imshow(nb),title('NOISE WITHOUT USING FUNCTION');