How to concatenate GRAYSCALE and RGB images?

I'm trying to concatenate a graysacale and rgb image but it shows error.

This is the code

>> A = imread('bird.jpg');
>> B = rgb2gray(A);
>> imshow(A),imshow(B);
>> C = cat(2,A,B);
Error using cat
Dimensions of arrays being concatenated are not consistent.

Can someone help me out?

I want this effect which is shown in given image

Answer 1

[Sai Bhargav Avula]

Hi, If just want to stitch them you can try using the montage() function of matlab.

Hope this helps!

[edusadiq]

Please explain it in MATLAB with the help of code

[Sai Bhargav Avula]

imRGB = imread('bird.jpg');
imGray = rgb2gray(imRGB);
figure
montage({imGray, imRGB},'Size', [1 2])

This code should give the expected result.

[edusadiq]

Yes, it worked 100%.

Thank you Sai Bhargav Avula

[DGM]

If the goal is to produce a composite image for further processing (or saving) and you want something with the abilities of montage(), you can also use IPT imtile() instead.

Answer 2

[DGM]

Alternatively, you can expand the grayscale image. Assuming the images have compatible geometry, they can then be edge-concatenated as normal.

% an RGB image and a mono image
RGB = imread('peppers.png');
I = rgb2gray(RGB);

% expand the single-channel image
Irgb = repmat(I,[1 1 3]);

% concatenate the images
outpict = [Irgb RGB];

imshow(outpict)