error occured when image-size isn't 512 * n

[hazy-wu]

dear author:
I notice that if the image size isn't 512 x 512, it will have some error. I use image size 1280 x 496 and i got tensor size error at calculate puzzle module:the original feature is 31 dims and re_feature is 32 dims. So i have to change image size to 1280 x 512 and i work.
So i think this maybe a little bug. It will better that you fixed it or add a notes in code~
Thanks for your job!