Channel in Digital Image Processing

I don't have very knowledge about digital image processing. I tried myself. If you help me, i will be very happy.

My tried code block:

I=imread('C:\Users\metec\Desktop\608918.jpg'); %2048x1024 image

[r c]= size(I);

A=I(1:r/1,1:c/1);

B=I(1:r/1,c/1+1:c);

C=I(r/1+1:r,1:c/1);

D=I(r/1+1:r,c/1+1:c);

L=([B C;D A]);

figure, imshow(L), title('Image changed');

[Rooter Boy]

@Image Analyst Sir, can you help me?