# How to separate an image to rgb?

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Jitha on 31 Dec 2013
Edited: Sailesh Sidhwani on 29 Jul 2019
how to divide an image into its r,g,and b colour planes,

Image Analyst on 31 Dec 2013
No reshaping is needed. Simply extract the color channels you need:
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
Then, to reverse the process and create an RGB image from three separate color channels:
% Recombine separate color channels into a single, true color RGB image.
rgbImage = cat(3, redChannel, greenChannel, blueChannel);

nur liyana zamri on 14 May 2017
This code didnt work
Walter Roberson on 14 May 2017
This code would definitely work if you have an RGB image stored in a variable named rgbImage .
It is possible, however, that this is not what you want done. What you might want done might be
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
z = zeros(size(rgbImage), class(rgbImage));
redImage = z; redImage(:,:,1) = redChannel;
greenImage = z; greenImage(:,:,2) = greenChannel;
blueImage = z; blueImage(:,:,3) = blueChannel;
subplot(2,2,1); image(rgbImage);
subplot(2,2,2); image(redImage);
subplot(2,2,3); image(greenImage);
subplot(2,2,4); image(blueImage);

Sailesh Sidhwani on 25 Oct 2018
Edited: Sailesh Sidhwani on 29 Jul 2019
Starting R2018b, Image Processing Toolbox has a new function "imsplit" which does exactly this: https://www.mathworks.com/help/images/ref/imsplit.html

ES on 31 Dec 2013
will give I (a 3d array, of size [x,y,3] )where x and y are the dimensions of the image. 3 is for R, G, and B components.
To separate out the three components, you can do a
R = reshape(I(:,:,1),[],1);
G = reshape(I(:,:,2),[],1);
B = reshape(I(:,:,3),[],1);

M on 31 Dec 2013
Try manual thresholding

#### 1 Comment

Image Analyst on 31 Dec 2013
??? Huh???? How could that work?

atersaw tigyhun on 29 Jul 2019
Edited: atersaw tigyhun on 29 Jul 2019
hahaha too long

Negesse Tadesse on 29 Jul 2019