UV automaticly squeezed without my permission

[salt サルト]

Before posting this, I tried many way to solve this myself, but I failed.
Here is my issue :
http://imgur.com/796EaNe
I unwrapped my model and everything looks fine.
but then workshop requirement said it must be 128W x 256H
so I create new image and use that size.
it turned to be like this
http://imgur.com/pAuvbsE
Apparently, my UV was squeezed, and I don't want that.
I want to have 128x256 image with 256x256 UV map.
Anyone know how to solve this?
-
(Note : I tried new image first then unwrap it, it stills the same)

[HellJumper]

Don't actually change the size of the UV. Just push everything to one half the size of the square.

[salt サルト]

@HellJumper
I tried it, and it still revolves around the same problem
the object supposed to be all black ( I'm testing if your advices work or not )
http://imgur.com/JS2PGIR
or maybe i did something wrong ?

[salt サルト]

*FIX : I noticed it can be solved using "Project from view " from your videos, but what make difference between Project from view and normal Unwrap ? I formerly use normal Unwrap for all of my models

[HellJumper]

It shouldn't make a difference how you unwrap it as long as the unwrap turns out ok (no giant stretches or weirdness). Projection unwrapping is a useful tool for more complicated shapes, and you should try to use it when you can.