I am applying dtw2 to an image (512*512)and after level 1 decomposition, I am getting approximation(256*256) and other details. How can I scale up only the 256*256 approximation to 512*512 size?

I am applying a discrete wavelet transformation on an image(suppose of size512*512) . Then I am getting 4 subband images after level 1 decomposition(approximation, horizontal,vertical and diagonal details) each of size 256*256.

now I want this approximation details scaled up in the size of 512*512.