why the local generator can't enlarge image size?

[DejaVuyan]

I want to enlarge images size by pix2pixHD model,for example: when I input image 256*256,the local generator can enlarge the image size to 512*512,when I use 2 local generator,it can enlarge the image size to 768*768.But it did not achieve this effect，it will output the image size as same as the input image size；when I chekout the LocalEnhancer in network.py , I found the number of down-sampling modules is the same as up-sampling,Why is that?Pix2pixHD how to achieve super resolution？