I am now trying to dynamically insert a Canvas component with an image
component inside of it. I need to re-used the code for many images.
Apparently it is only working if I give the canvas a width and height, which
needs to be the size of the image file.

How can I do this?

Images are just display objects. You should be able to grab the measuredWidth
and measuredHeight properties off of it to determine how big your canvas needs
to be. If you're dynamically changing the source of your image, watch for the
dataChange event that the image dispatches when its source changes.