Current image width?

I'm scaling an UI image while preserving its aspect ratio, sometimes causing the rect transform to outgrow the image size in width. I want another UI object, a green plain, to retain the width of the image with, not the rect transform width.

In short, I need to get the image width. The scaled width, not the source image width.
Any help would be appreciated... everything I have tried only gives the original width, not run-time scaled width.

 

See attachment for what I mean.

 

not exactly sure i understand what you are trying to do but try using rectTransform.sizeDelta for manipulating the size. it accounts for changing resloutions.