MATLAB - Splitting an image converts the blocks into grayscale - matlab

Question

Using MATLAB, I am trying to convert a randomly sized image into four equal blocks. I am working with "for" loops to create blocks. The problem I am facing is that these blocks are being converted into gray scale whereas I want the blocks to retain their original form i.e. RGB channel. Here is the code I am using:
clear all;
img1 = imread('ABC.png');
[rs, cols, colorchan] = size(img1);
rnew = int32(rs/2);
cnew = int32(cols/2);
for i = 1:4
for j = 1:4
imgij = img1((i-1)*rnew+1:i*rnew, (j-1)*cnew+1:j*cnew);
figure();
imshow(imgij);
%do some other stuff here%
end
end
I am new to MATLAB and that's the best I could do myself. Can somebody please tell me how to retain the original form of every block of the parent image? Any help will be highly appreciated.

Answer 1

You have considered only the width and height of the image. But actually for a colour image, colour is the 3rd dimension in Matlab. Try the following code.
img = imread('onion.png');
figure; imshow(img);
w = size(img,2); % width of the original image
h = size(img,1); % height of the original image
wm = floor(w/2); % middle of the width
hm = floor(h/2); % middle of the height
figure;
imgtl = img(1:hm,1:wm,:); % top left image
subplot(2,2,1); imshow(imgtl);
imgtr = img(1:hm,wm+1:w,:); % top right image
subplot(2,2,2); imshow(imgtr);
imgbl = img(hm+1:h,1:wm,:); % bottom left image
subplot(2,2,3); imshow(imgbl);
imgbr = img(hm+1:h,wm+1:w,:); % bottom right image
subplot(2,2,4); imshow(imgbr);
Original image:
Partitioned image: