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I have two separate gray scale images im1 (Fig1) and im2 (Fig2) each of size 50 by 50 that are displayed here by color coding them. When I combine them together using cat() command and then display the result of concatenated images, they get displayed side by side (Fig3). However, if I create a third image by replicating either the first of the second image and then display the concatenation of the 3 images I get a single image (Fig4). I don't understand how the merging for the RGB (3 dimensions) could be possible whereas for the conversion to grayscale the merging did not happen. How can I get a single image using the two images im1 and im2 merged or overlayed whichever is legally possible and not side by side? Si how do I overlay im1 and im2 to get a single image and display it by color coding?

imgGray = cat(2,im1,im2);
imshow(imgGray)
imgGray = cat(2,im1,im2);  
imshow(imgGray)
imagesc(imgGray)
im3=im1;
imgColor = cat(3,im1,im2,im3);  
imagesc(imgColor)

out

Sm1
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2 Answers2

1

You can to do it "manually":

  • Use ind2rgb for converting each Grayscale image to RGB with "color coding".
  • Compute average of two RGB images for getting "fused image".

Here is a code sample: 

% Use cameraman as first image, and resized moon for the second image (just for example).
I1 = imread('cameraman.tif'); % I1 is uint8 Grayscale
I2 = imresize(imread('moon.tif'), size(I1));  % I2 is uint8 Grayscale

% Convert images to RGB using parula color map (you may choose any color map).
J1 = ind2rgb(I1, parula(256)); % J1 is double RGB (three color planes in range [0, 1]).
J2 = ind2rgb(I2, parula(256)); % J2 is double RGB (three color planes in range [0, 1]).

% Fuse J1 and J2 "manually".
alpah = 0.5; % Using alpah=0.5, gives average of J1 and J2.
K = J1*alpah + J2*(1-alpah); %K is is double RGB.
K = im2uint8(K); % Convert K to uint8 (im2uint8 multiplies pixels by 255, and convert to uint8).

%Display result
figure;imshow(K);

Result:
enter image description here

Rotem
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1

You can also just add them to each other (after normalizing them) and have a single colormap represent it all

imagesc(I1+I2);

enter image description here

or if you want to set transparency according to the color and intensity you can add

alpha color
alpha scaled
bla
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  • Thank you for your answr, it seems straightforward. But how do I normalize the images as you mentioned in the first step? – Sm1 Feb 17 '20 at 23:08
  • first make sure that `I=double(I)`, so any operation you are doing will not mess with the information in the image. Normalize means wither setting the maximun to 1 via `I=I./max(I(:))` or deviding by the total intensity of the image `I=I./sum(I(:))`. see what makes sense to you... – bla Feb 18 '20 at 03:21