NSImageView Unproportional Zoom

I had this weird problem when I tried to implement a zoom functionality in my hobby project, a manga reader called Yomu. When I tried to zoom an NSImageView programmatically it's being zoomed unproportionally, my expectation was the image should be stretched horizontally and vertically without moving from its center point. It was like this

Zoom 100%

Zoom 140%

Damn, there was an ugly gap :( between header border and the image. I had a hard time finding the solution, it took me almost 3 days to debug this problem (maybe because I'm a newbie). It turns out the solution is really simple, by default apple will set image view to scale proportionally down, changing it to proportionally up or down will fix the problem.

The culprit T_T

Fixing it 🍻