Matlab creating windows on image

Hi, I really need help with sliding windows in matlab.

My algorithm is as follows:

1. Create 32x32 sliding window on image
2. Check mean intensity of each window
3. If mean intensity is less than 200, discard the window
4. The remaining 32x32 windows are divided into 8x8 windows.

I am really struggling to find any help with this! Can anyone please help meee!

Thanks