How to scan a gray image in inverse-s order and calculate the differences of the adjacent pixels and plot a histogram of difference matrix?

somebody please tell me how to do it in matlab.

Answer 1

[Image Analyst]

You can use conv2(), or graycomatrix(). You can set up a kernel defining "adjacent" then call conv() then histogram()

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

%===============================================================================
% Read in 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')
  % The file doesn't exist -- didn't find it there in that folder.
  % Check the entire search path (other folders) for the file by stripping off the folder.
  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
rgbImage = imread(fullFileName);

% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(rgbImage)
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  %   grayImage = rgb2gray(rgbImage);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  grayImage = rgbImage(:, :, 1); % Take red channel.
else
  grayImage = rgbImage; % It's already gray scale.
end
% Now it's gray scale with range of 0 to 255.

% Display the image.
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Image', 'FontSize', fontSize, 'Interpreter', 'None');
axis('on', 'image');
hp = impixelinfo();

%------------------------------------------------------------------------------
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.04, 1, 0.96]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;

% Define kernel
kernel = [-1, 1];
diffImage = conv2(double(grayImage), kernel);

% Display the image.
subplot(2, 2, 2);
imshow(diffImage, []);
title('Difference Image', 'FontSize', fontSize, 'Interpreter', 'None');
axis('on', 'image');
hp = impixelinfo();
drawnow;

% Display the histogram
subplot(2, 2, 3:4);
histogram(diffImage);
grid on;
xlabel('Difference Value', 'FontSize', fontSize);
ylabel('Count', 'FontSize', fontSize);
title('Histogram of Difference Values', 'FontSize', fontSize);

[eram fatima]

I dont want to increase the size of image.Below is the algorithm im trying to implement, For an N-pixel 8-bit grayscale host image H with a pixel value xi , where xi denotes the grayscale value of the ith pixel, 0 ≤ i ≤ N − 1, xi ∈ Z, xi ∈ 0, 255. 1) Scan the image H in an inverse s-order. Calculate the pixel difference di between pixels xi−1 and xi by di = xi , if i = 0, |xi−1 − xi |, otherwise. 2) Determine the peak point P from the pixel differences. 3) Scan the whole image in the same inverse s-order as in Step 1. If di > P, shift xi by 1 unit yi= xi , if i = 0 or di < P, xi + 1, if di > P and xi ≥ xi−1, xi − 1, if di > P and xi < xi−1, where yi is the watermarked value of pixel i .

[Image Analyst]

Then use the same option:

diffImage = conv2(double(grayImage), kernel, 'same');

[eram fatima]

</matlabcentral/answers/uploaded_files/132628/png.PNG> this is how i want to access the pixels...however with conv2() , the pixels are accessed row wise.

[eram fatima]

Iam attaching an image of the order in which pixels are to be accessed...

[attiqa iltaf]

hi, hope you get the understanding of code how to scan image invers 'ss wise . kindly share it with me i am working on compression. i still couldn't get the desire and