How to show histogram of RGB image in Matlab?

Question

I read an image in matlab using

input = imread (\'sample.jpeg\');

Then I do

imhist(input);

It gives this

Answer 1

imhist displays a histogram of a grayscale or binary images. Use rgb2gray on the image, or use imhist(input(:,:,1)) to see one of the channel at a time (red in this example).

Alternatively you can do this:

hist(reshape(input,[],3),1:max(input(:))); 
colormap([1 0 0; 0 1 0; 0 0 1]);

to show the 3 channels simultaneously...