How to split matrix into 2 subsets

hello everyone, i want ask about my project and my program. i have a image : </matlabcentral/answers/uploaded_files/22111/coba1.png> and i want to split into block nxn, for example : for one secret image with 16x16 pixel, i want to split into 4x4 for each block. So i have 16 block with 4x4 pixels. Then, for each block i want to spilt into 2 subsets with conditional H(C^q)-(H(C^q+1)<=1. </matlabcentral/answers/uploaded_files/22112/example.png>. Thanks before :).