How would i extract ONLY even numbered elements of an image?

I have an image that I am suppose to `Half' the size of the image (i.e.  reducing it to 256x256) by extracting only even numbered elements. This is my code so far:

% Part i.

imgroup0=imread('selfie2.tif');

A1= rgb2gray(imgroup0);

imgroup1=imresize(A1, [512 512]);

% Part ii.

evens=imgroup1(mod(imgroup1,2)==0);

But i dont understand how mod will help me 'extract' the even numbers from the image or how i would display it afterwards. Can someone explain?

Answer 1

[Bhaskar R]

Part ii

% for even values
even_values = imgroup1(mod(imgroup1, 2) == 0);
% for display purpose
evens = imgroup1.*uint8(mod(imgroup1, 2) == 0);
figure, imshow(evens);  

[Jenalyn Palacios]

Thank you!!