MATLAB Answers

Create a mask for different values

2 views (last 30 days)
I want to subtract two images and show the results in another figure. For instance, if the subtraction matrix has 0 value indicate the elements with black, if it has negative value show them with red and if it has positive value show with blue. How can I do that?

Accepted Answer

Walter Roberson
Walter Roberson on 17 Feb 2021
%sample data
firstImage = imread('cameraman.tif');
secondImage = imresize( rgb2gray( imread('flamingos.jpg') ), size(firstImage));
%assuming grayscale images
imgdiff = double(firstImage) - double(secondImage);
n0p = sign(imgdiff); %-1 for negative, 0 for equal, 1 for positive
%add 2 to n0p to get a 1-based index
cmap = [1 0 0; 0 0 0; 0 0 1]; %red, black, blue
diffImg = reshape(cmap(n0p+2,:), size(imgdiff,1), size(imgdiff,2), 3);
%show it off
subplot(3,1,1)
imshow(firstImage);
title('cameraman')
subplot(3,1,2)
imshow(secondImage);
title('flamingos')
subplot(3,1,3)
imshow(diffImg);
title('color difference image')
  4 Comments
Walter Roberson
Walter Roberson on 24 Feb 2021
%sample data
firstImage = imread('cameraman.tif');
secondImage = imresize( rgb2gray( imread('flamingos.jpg') ), size(firstImage));
%assuming grayscale images
imgdiff = double(firstImage) - double(secondImage);
n0p = sign(imgdiff); %-1 for negative, 0 for equal, 1 for positive
%add 2 to n0p to get a 1-based index
cmap = [1 0 0; 0 0 0; 0 0 1]; %red, black, blue
diffImg = reshape(cmap(n0p+2,:), size(imgdiff,1), size(imgdiff,2), 3);
%show it off
subplot(3,1,1)
imshow(firstImage);
title('cameraman')
subplot(3,1,2)
imshow(secondImage);
title('flamingos')
subplot(3,1,3)
imshow(diffImg);
title('color difference image')
hold on
names = {'negative', 'equal', 'positive'};
for K = 1 : 3
L(K) = plot(nan,nan,'s', 'markeredgecolor', cmap(K,:), 'markerfacecolor', cmap(K,:));
end
hold off
legend(L, names, 'location', 'eastoutside')

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!