Re-size Image in ExtendScript

I have a script for After Effects, I want the user to be able to set a max dimmensions on an image. I'm getting the dimmensions with

AVItem.height & AVItem.width

But how do I change these values? In the documentation I've found:

"

In a CompItem, the value is linked to the composition, and is read/write.

In a FootageItem, the value is linked to the mainSource object, and is read/write only if the mainSource

object is a SolidSource. Otherwise, it is read-only.

"

In my case this is not a 'SolidSource' type, how can I change the dimmensions? Any work arounds? Besides creating a new CompItem and inserting the image and then changing the values of the CompItem