Adding Noise to the Image

How do I apply "salt" noise to the grey - scale image. Function need to generate salt noise only not the pepper.

Answer 1

[Image Analyst]

Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
format longg;
format compact;
fontSize = 20;

%===============================================================================
% Read in a standard MATLAB gray scale demo image.
folder = fileparts(which('cameraman.tif')); % Determine where demo folder is (works with all versions).
baseFileName = 'cameraman.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the original gray scale image.
subplot(1, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 

% Initialize an output image.
noisyImage = grayImage; % Initialize
% Get 5,000 random locations
noiseIndexes = randperm(numel(grayImage), 5000);
% Add noise
noisyImage(noiseIndexes) = 255;
% Display the noisy image.
subplot(1, 2, 2);
imshow(noisyImage, []);
title('Noisy Image', 'FontSize', fontSize);
axis on;

[Steve]

Thank you

Answer 2

[Arun Kumar]

%Prepare workspace

clear ; clc; close all;

%Read Imag

I=imread('cameraman.tif');

%create a random matrix

randM=rand(size(I));

% default density

d=.05;

%saturated value

randM(randM<d)=255;

%Add noise

I=uint8(double(I)+randM);

%show image

imshow(I)

[Steve]

Thank you