How do I display the red channel of an image in Matlab?

Question

I have a 3D matrix im which represents an RGB image. I can do

imshow(im)

to display the image.

I want to display only one of the RGB channels at a time: I want to display the red channel and I want it to appear red.

I've tried

imshow(im(:,:,1))

but it displays the grayscale image (which is not what I want).

How do I display the red channel and make it appear red?

Answer 1

I have three proposals for you.

1. Use the imagesc function and choose a red color palette.

2. Clear the other color channels: im(:,:,2:3) = 0; imshow(im);

3. Use the ind2rgb function with a color map you build accordingly.

Answer 2

Try this:

% display one channel only
clear all;

im=imread('images/DSC1228L_512.jpg');
im_red = im;
im_green = im;
im_blue = im;

% Red channel only
im_red(:,:,2) = 0; 
im_red(:,:,3) = 0; 
figure, imshow(im_red);

% Green channel only
im_green(:,:,1) = 0; 
im_green(:,:,3) = 0; 
figure, imshow(im_green);

% Blue channel only
im_blue(:,:,1) = 0; 
im_blue(:,:,2) = 0; 
figure, imshow(im_blue);