Adding Shaped Noise to a picture

Hello Experts,

Given double image matrix, I need to add shaped noise to the image with given NxM size of the shape. It should be salt & pepper with given variance. The structure of the noise is also given with the matrix.

I need to add such noise to the picture say of the shape "+".

What I did refuse to work and I need your assistance:

I = imread('image file'); I = double(I)/255;

Defining N = zeros(size(I)); ni = imnoise(N,'salt & pepper', given alpha); ni = conv2(N,T,'same'); where T is the given shape of the noise.

ni1 = max(I,ni);

Please try to help me, Thanks a lot in advance.

Answer 1

[Image Analyst]

I don't understand. Salt and pepper noise does not have a variance. What do you mean by "shape"? Do you mean that noise only occurs in a certain region of interest of the image, or do you mean that the noise has a certain spectrum (in which case it's not salt and pepper noise anymore)?

Demo if you want noise in a mask area that you draw:

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

% Read in a standard MATLAB gray scale demo image.
folder = 'C:\Users\Mark\Documents\Temporary';
folder = 'D:\Downloads';
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
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.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, '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);
% Display the original gray scale image.
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') 

promptMessage = sprintf('Click "Draw Mask" to draw a mask.  Left click to anchor points, but right-click to finish it.\nor Cancel to quit.');
button = questdlg(promptMessage, 'Draw Mask', 'Draw Mask', 'Cancel', 'Draw Mask');
if strcmp(button, 'Cancel')
  return;
end
[mask verticesX verticesY] = roipolyold();

% Re-display the original gray scale image in a small subplot
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);

% Display the binary image.
subplot(2, 2, 2);
imshow(mask, []);
title('Binary Mask Image', 'FontSize', fontSize);

% Create an image with noise everywhere.
% (Not needed, just doing for fun.)
noisyImage = imnoise(grayImage, 'salt & pepper', 0.05);
% Display the noisy image.
subplot(2, 2, 3);
imshow(noisyImage, []);
% Display the mask outlines.
hold on;
plot(verticesX, verticesY, 'r-');
title('Noisy Image', 'FontSize', fontSize);

% Create a masked image where it's noisy only within the polygon they drew.
maskedImage = grayImage; % Initialize
maskedImage(mask) = noisyImage(mask);
% Display the masked noisy image.
subplot(2, 2, 4);
imshow(maskedImage, []);
title('Masked Noisy Image', 'FontSize', fontSize);

[Steve]

1) Getting image

2) Transforming to double(I)/255

I need to add salt and pepper noise on the picture BUT with my shape like V or + or lines.

After adding such noise you will see specific shaped noise not the random one.

Hope it's more understandable..

[Steve]

and I meant density of the S&P sorry..

[Steve]

The noise shape given in a matrix

[Image Analyst]

OK, see edited version above that now has demo code to add noise in a V-shaped polygon that you can draw.

Answer 2

[Kiranraddi morab]

Hey i wanted to detect the noise type by using spectrum of noise ,is it possible to do if so please help me (how to detect noise type)