color pixels in image

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linou landini
linou landini on 11 Dec 2021
Commented: Image Analyst on 15 Dec 2021
I want to color the pixels with color , like this example
  5 Comments
Chunru
Chunru on 12 Dec 2021
How do you define the pixes in two images are same or different?

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Answers (4)

Image Analyst
Image Analyst on 12 Dec 2021
Edited: Image Analyst on 12 Dec 2021
What you ask is so simplistic as to be useless, like some trivial homework assignment. Untested code:
equalMask = logical(max(image1 == image2, [], 3));
outputEqual = imoverlay(image1, equalMask, 'g')
outputDifferent = imoverlay(image1, ~equalMask, 'r')
I think what you really want is to know what regions of the image have changed from "before" to "after", like the region has experienced an earthquake or fire or some other type of catastrophe. Then you know where to send emergency services, i.e. to the most heavily damaged areas.
This has been extensively studied and there are papers on it. I give you references below. Look over the papers and pick one and code it up. I do not have any of these algorithms already coded up and ready to give you. You can always ask the authors for source code.
  3 Comments
Image Analyst
Image Analyst on 13 Dec 2021
@linou landini those images are different sizes. Please upload two images that have exactly the same dimensions as each other.

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Voss
Voss on 12 Dec 2021
Here's an approach that may work for you. (It uses the two black-and-white images you posted to your comment here. I don't know what data type your images are stored as, but when I downloaded each of those, I got a 3D matrix of uint8's, so the code assumes that. Since they are different sizes, the code cuts each one down so they are the same size.) This will make an image that has a green pixel where the input images are the same and a red pixel where they are not, as specified in your comment here.
image1 = imread('image1.png');
image2 = imread('image2.png');
image1(end,:,:) = []; % cut them down to size. you will need to change this for different
image2(:,end,:) = []; % pairs of images or make sure they are the same size beforehand
[m,n,p] = size(image1);
image_out = zeros([m n p],'uint8'); % make an output image of the same size and type
for i = 1:m
for j = 1:n
pixel_same = true;
for k = 1:p
% pixels are the same if all channels (i.e., R, G, B) are the
% same, so as soon as any channel is different, we know the
% pixel is different, so we stop checking (i.e., break)
if image1(i,j,k) ~= image2(i,j,k)
pixel_same = false;
break
end
end
if pixel_same
image_out(i,j,:) = [0 255 0]; % green pixel in output image
else
image_out(i,j,:) = [255 0 0]; % red pixel in output image
end
end
end
% do something with the result:
imwrite(image_out,'image_out.png');
imshow(image_out);

DGM
DGM on 12 Dec 2021
As @Benjamin noted, your example binarized images are mismatched in size and are actually RGB images. I'm going to guess that this is because they were saved from a figure.
As a consequence, the first two sections of this code are entirely a matter of fixing that. If you have two logical or floating-point images of the same size, you'll only need to do the last part.
% images as provided are RGB uint8; convert back to logical
A = rgb2gray(imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/832005/image.png'))>128;
B = rgb2gray(imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/832010/image.png'))>128;
% image sizes don't match; you'll have to fix that somehow.
A = A(1:end-1,:);
B = B(:,1:end-1);
% combine images, cast
C = im2double(cat(3,A,A & B,B));
% display it
imshow(C)
  2 Comments
DGM
DGM on 14 Dec 2021
Again, I doubt that the images you posted are the exact same images that you're working with. You'll need to do whatever is required to make sure that the two images are the same size. If they're already the same size, then they don't need to be cropped as in my example.
The example images are 88x89x3 and 87x90x3 respectively. If their sizes mismatch and are different than the example images, then they'll have to be padded/cropped as necessary.

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Image Analyst
Image Analyst on 13 Dec 2021
@linou landini try this:
% Demo by Image Analyst, December, 2021.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clearvars;
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
fprintf('Beginning to run %s.m ...\n', mfilename);
%-----------------------------------------------------------------------------------------------------------------------------------
% Read in image.
folder = [];
baseFileName = 'image1.png';
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~isfile(fullFileName)
% 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
fullFileName = fullFileNameOnSearchPath;
end
image1 = imread(fullFileName);
[rows, columns, numberOfColorChannels] = size(image1)
if numberOfColorChannels == 3
% Image is color. We need gray scale. Convert to gray scale.
image1 = rgb2gray(image1);
end
% Display the image.
subplot(2, 2, 1);
imshow(image1, []);
axis('on', 'image');
caption = sprintf('Original Image : "%s"', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Read in image.
folder = [];
baseFileName = 'image2.png';
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~isfile(fullFileName)
% 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
fullFileName = fullFileNameOnSearchPath;
end
image2 = imread(fullFileName);
[rows2, columns2, numberOfColorChannels2] = size(image2)
if numberOfColorChannels2 == 3
% Image is color. We need gray scale. Convert to gray scale.
image2 = rgb2gray(image2);
end
% Make sizes match
if rows ~= rows2 || columns ~= columns2
message = sprintf('Images are of different sizes.\nI will resize image2 to match image1.')
uiwait(warndlg(message))
image2 = imresize(image2, [rows, columns]);
end
% Display the image.
subplot(2, 2, 2);
imshow(image2, []);
axis('on', 'image');
caption = sprintf('Original Image : "%s"', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
hFig1 = gcf;
hFig1.Units = 'Normalized';
hFig1.WindowState = 'maximized';
% 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.
hFig1.Name = 'Demo by Image Analyst';
%--------------------------------------------------------------------------------------------------------
% Segment (mask) the image.
equalMask = image1 == image2;
% Display the equal mask image.
subplot(2, 2, 3);
imshow(equalMask, []);
axis('on', 'image');
caption = sprintf('Mask Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Now make an all red image.
redImage = 255 * ones(rows, columns, 'uint8');
zerosImage = zeros(rows, columns, 'uint8');
redImage = cat(3, redImage, zerosImage, zerosImage);
% Burn in green where they are equal.
outputEqual = imoverlay(redImage, equalMask, 'g');
% Display the color coded image.
subplot(2, 2, 4);
imshow(outputEqual, []);
axis('on', 'image');
caption = sprintf('Red = Not Equal. Green = Equal');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
  5 Comments
Image Analyst
Image Analyst on 15 Dec 2021
OK, you're welcome. Sorry I/we couldn't help though -- I did everything I could.
Just to complete the question though, you can post your own code as a new Answer (so I can see how it's different than mine) and mark yours as the "Accepted" answer, and the other Answers you can click the "Vote" icon for it you want to award DGM and me "reputation points."

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