Help for 'imread'

Hi dear, Can someone help me telling me what this means?

img = imread('imgs/lego.png');

blue = img(:,:,1);

What return in 'blue'?

Answer 1

[Walter Roberson]

If imgs/lego.png is an RGB color image, then "blue" will hold the red channel information. If imgs/lego.png is a grayscale image, then "blue" will hold the brightness information. If imgs/lego.png is an indexed (pseudocolor) image, then "blue" will hold the index information but there will be no information available about what color each distinct index is to correspond to.

The first pane, (:,:,1) of an RGB image is the Red information. The second pane, (:,:,2) is the Green information. The third pane, (:,:,3) is the Blue information.

[Filipe Ribeiro]

Thanks Walter!

[Image Analyst]

Filipe, I'd recommend you use better variable names. "blue" for the red channel is a very deceptive name. Here is the snippet I like to share:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);