what's the problem in this code, while i'm trying to extract the 3 channels of an RGB image?

while i'm reading an rgb video, i wanted to extract for each frame its 3 channels(R,G and B) but the results looks weird, here there is the code i uused:

videoReader = vision.VideoFileReader('video.avi');
J=0;
while ~isDone(videoReader);
    J=J+1
    frameRGB = step(videoReader); 
    figure;imshow(frameRGB);
    imwrite(frameRGB,'frame.jpg');
    a=imread('frame.jpg');
    figure,imshow(a(:,:,1));
    figure,imshow(a(:,:,2));
    figure,imshow(a(:,:,3));
  end

ps: i used writing frame , to make sure about results

[Image Analyst]

What's weird? It looks like you should get the 3 color channels in separate figures. Each one will be grayscale, of course, because they are not true color images anymore, and you have not applied a colormap to the gray scale images either. What were you expecting?

Answer 1

[Walter Roberson]

R = frameRGB;
R(:, :, 2:3) = 0;
imshow(R) ;

and likewise for the other two panes, setting the channels except for the one of interest to 0

[bay rem]

can i know you you really did in here? i don't understand and how can i extract the 2 other channels

[Meghana Dinesh]

Well, do you know how an RGB image is stored in MATLAB? It has three channels, R, G and B.

To view only the R channel, make G and B channels zero. (As shown above)

To view only the G channel, make R and B channels zero.

 G = frameRGB;
 G(:, :, 1) = 0;
 G(:, :, 3) = 0;
 imshow(G) ;

To view only the B channel, make R and G channels zero.

 B = frameRGB;
 B(:, :, 1:2) = 0;
 imshow(B) ;

It is very trivial, and has already been discussed in several questions on this forum. Perhaps you would like to do a simple google search.